Evaluation of Best Production Practices for Olive (Olea europaea) in Oregon. Part I

Final report for SW18-057

Project Type: Research and Education
Funds awarded in 2018: $193,575.00
Projected End Date: 03/31/2022
Grant Recipient: Oregon State University
Region: Western
State: Oregon
Principal Investigator:
Expand All

Project Information

Abstract:

Olives are a high value specialty crop that continues to expand its cultivation in Oregon with some limitation, mainly due to winter climatic and environmental conditions that directly affect field establishment and plant survival. In the Pacific Northwest, low winter temperatures can negatively affect tree development during establishment, particularly during the planting year. Oregon growers are also facing a shorter growing season than traditional growing regions to ripen their fruit, in addition to a lack of scientific research-based knowledge of best production practices for the region. Production techniques to assist with orchard survival and possible cultivars that may be sufficiently resistant and produce quality fruit to adapt the crop to these conditions in Oregon’s shorter ripening season, must be identified. An additional important goal of the project is to reduce the cost of orchard establishment by providing information on propagation practices to facilitate local availability of adapted cultivars and for growers to be able to produce their own planting stock. Unfortunately, as most olives are produced in milder, traditional growing climates, comprehensive, peer reviewed and replicated relevant information on the production practices, propagation, and resistance to winter damage of olive cultivars does not exist for our region where winter temperatures are lower and growing seasons shorter. Our project is addressing these challenges by: a) obtaining multiple cultivars from multiple sources as cuttings or plants, rooting them, propagating them to experimental numbers, and evaluating them in a replicated, multi-year commercial field setting in Aurora OR (USDA hardiness zone 8b), and at the same time in a collaborative effort with growers that already have trees of different ages; b) replicated field trials at the North Willamette Research and Extension Center (NWREC) and Oregon State University Woodhall III Vineyard where potted nursery plants of commercial age of four cultivars currently grown in Oregon orchards will be both planted directly in the field, and also kept in protected structure over winter after transplanting to 3 and 6-gallon pots as they develop in size and age, to assess their respective susceptibility to freeze injury after field planting; and c) evaluating propagation season (by obtaining cuttings at different times in the year), rooting hormone (type and concentration), cultivar rooting ability, and growing substrates. As planned, the project has continued research and extension activities, but final outcomes have been delayed due to the global COVID pandemic. Once the data has been collected and analyzed for all three project components, final study results will be shared with industry and the public through multiple media forms and publications, as well as field days and presentations hosted in collaboration with the olive growers in Oregon. 

Project Objectives:

The main goals of the project are to assist in making olive production economically feasible and reduce climatic limitations (winter damage) during establishment of orchards for olive growers. In order to achieve these goals the specific project objectives include:

  1. Determine most effective olive propagation techniques for Oregon by evaluating timing, rooting hormones, cultivar rooting ability, and propagation medium to successfully root potentially locally-adapted cultivars.
  2. Establish the relative winter damage resistance (freezing cold hardiness) of olive cultivars through a multi-year field evaluation, to determine which are best adapted to our region and produce high-quality fruit in western Oregon.
  3. Evaluate overwintering and up-potting practices to achieve rapid/successful orchard establishment and determine if plant size and maturity at time of planting influences subsequent cold hardiness as well as comparing planting location, season, and orchard floor management practices.
  4. Conduct a comprehensive Oregon olive grower survey to determine grower needs and research priorities. Disseminate the information obtained via research and grower survey to industry stakeholders, existing and potential growers, project participants, and the general public via tours, visits, in-person communications, written media, social media, and classes, during and following the duration of the project.

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Neil Bell (Educator and Researcher)
  • Heather Stoven (Educator and Researcher)
  • Tessa Barker (Educator and Researcher)
  • Bogdan Caceu - Producer
  • Paul Durant - Producer
  • Marni Redding - Producer
  • Louise Ferguson (Educator)
  • Dan Flynn (Educator)
  • Tom Vail - Producer
  • Myron Redford - Producer
  • Daniel Battaglia - Producer
  • Phil Gouy - Producer
  • Chris Barry - Producer
  • Peter Vetter - Producer
  • Compton Chase-Lansdale - Producer
  • Steve Saxton - Producer

Research

Hypothesis:

This project is not specifically based on one hypothesis but multiple objectives that ultimately seek to ascertain how viable olive production is in Oregon and the Pacific Northwest as well determine the best practices for orchard establishment. 

The main goals of the project are to assist in making olive production economically feasible and reduce climatic limitations for olive growers. In order to achieve these goals the specific project objectives include:

  1. Determine most effective olive propagation techniques for Oregon by evaluating timing, rooting hormones, cultivar rooting ability, and propagation medium to successfully root potentially locally adapted cultivars.
  2. Establish the relative winter damage resistance (freezing cold hardiness) of olive cultivars through a multi-year field evaluation, to determine which are best adapted to our region and produce high-quality fruit in western Oregon.
  3. Evaluate overwintering and up-potting practices to achieve rapid/successful orchard establishment and determine if plant size and maturity at time of planting influences subsequent cold hardiness as well as comparing planting location, season, establishment irrigation practices, and bed shaping and orchard floor management practices.
  4. Conduct a comprehensive Oregon olive grower survey to determine grower needs and research priorities. Disseminate the information obtained to industry stakeholders, existing and potential growers, project participants, and the general public via tours, visits, in-person communications, written media, social media, and classes, during and following the duration of the project.
Materials and methods:

Objective 1: Olive Propagation Study

Currently, olive growers in Oregon are reliant upon purchasing plant material from California for establishing and replacing trees in their orchards.  This is limiting to growers, as it reduces available cultivars to that which is often most appropriate for California, growers are reliant on nursery availability, and purchasing can be cost prohibitive due to available sizes and shipping. Secondly, growers are concerned about potential quarantines for diseases and pests present in California as well as their transfer to Oregon with infected plant material. Although a few local growers are able to propagate olives via cuttings, information about how to do so is not widely available and an accepted best method for this region has not yet been determined.  It is therefore necessary to provide replicated data on successful propagation techniques for the olive growers within Oregon due to our varying climate and resources.  Even though worldwide tissue culture of olives is gaining in popularity (Bati et al, 2006), due to current lack of knowledge regarding best cultivars for this region, it is more useful for Oregon growers to have documented information on how to have success with rooting of their own cuttings rather than produce research on tissue culture techniques.

This project component aims to compare semi-hardwood propagation techniques in a greenhouse at OSU’s North Willamette Research and Extension Center (NWREC) located 30 miles south of Portland in the Willamette Valley, as well as utilize grower facilities for olive grower-led propagation studies. The studies will be replicated by a grower as a means to gain experience in propagation as well as allowing us to determine the success of such proposed techniques under producer environments and facilities. The growers collaborating on the propagation studies will receive assistance with setting up their studies (instruction and labor for taking cuttings and sticking cuttings), provided propagation supplies (potting media, pots, etc.), and funding if needed for facility upgrades to help with standardization of the study, such as providing mist benches and heat mats. Training will be provided to growers on olive propagation techniques and procedures, assisting with the success of the trial and providing a background for future success in propagation, allowing them to be able to replicate the propagation on their own. We will communicate with growers via email or in person as needed while their studies are underway, as well as being available for questions.  We will collect the data from their facilities, with their involvement. The grower experiences will be documented before and after the trials, obtaining feedback on the trials. Three studies will explore four aspects of propagation: timing of collection and propagation of cuttings from orchards, rooting hormone type and concentration, cultivar rooting ability, and media substrate. 

The first study, performed in 2018 and repeated in 2019, evaluated the best timing for propagating cuttings in Oregon, along with rooting hormone type and concentration. Timing of taking propagative cuttings has been evaluated in other parts of the world (Fabbri et al, 2012), but has not been documented in our state or region. Three timings of collecting semi-hardwood cutting material were done: spring (May), summer (July) and fall (October).  The spring, summer, and fall timings utilized mist and the fall timing additionally utilized trays with a plastic dome for regulating humidity without mist. The fall timing without mist gave us the opportunity to collaborate with growers who do not have mist systems, allowing for grower experience in propagation and data regarding propagation in different environments. For each propagation timing, twenty-four 3-4” semi-hardwood cuttings of one easy-to-root cultivar (‘Arbequina’) were dipped in one of the rooting hormone treatments and then placed in a completely randomized design on a mist bench with bottom heat. The hormone treatments were a high and low concentration of IBA + NAA (2000ppm/1000ppm “2D” and 4000ppm/2000ppm “4D”, IBA/NAA respectively) and a low and high concentration of IBA only (3000ppm “3H” and 8000ppm “8H”).  These concentrations were chosen based on olive propagation literature (Fabbri et al, 2004, DeOliveira et al, 2003), and personal communication with regional olive propagators.  After three months, the cuttings were evaluated for rooting percentage, as well as number and length of roots. Olive growers received assistance with the evaluation, set up and oversight of the study at their facilities.

The second study occurred in 2019, was repeated in 2020, and evaluated soilless substrate media utilizing the cultivars ‘Leccino’ and ‘Picual’ with differing rooting capabilities (high and medium) according to Fabbri et al.  Sixteen cuttings each of the three cultivars were stuck in four soilless substrate mixes 1) 1:1 by volume ratio of horticultural peat moss and coarse propagation grade perlite (referred to as “PP11”), 2) 3:7 by volume ratio of horticultural peat moss and coarse propagation grade perlite (“PP37”), 3) 1:1 by volume ratio of coconut coir and coarse propagation grade perlite (“CP11”), and 4) 3:7 by volume ratio of coconut coir and coarse propagation grade perlite (“CP37”).  The rooting hormone concentration was determined based on results from the 2018 study and was 3000ppm IBA. Plants were placed on heated mist benches in a completely randomized design and at the end of three months rooting percentages, as well as length and number of roots for each of the treatments was determined.

The final propagation study took place in 2020 and combined the first two studies, focusing on cultivar rooting ability and rooting hormone.  Olive cultivars with comparatively high and medium rooting capabilities (‘Leccino’ and ‘Picual’) were tested with the two best performing rooting hormones (2000 ppm/1000 ppm IBA/NAA, and 3000ppm IBA), to determine if a best hormone can be chosen for different olive rooting abilities.  One rooting media that performed best in the second study (1:1 peat:perlite) was used, along with one timing (spring).  Twenty-four cuttings of each cultivar were dipped in one of the two rooting hormone treatments then completely randomized on a mist bench with bottom heat. At the end of three months rooting percentages, as well as length and number of roots for each of the treatments was determined.  Having this experiment replicated by growers was important to tie all the three studies together, allowing us and them to evaluate rooting hormones and cultivars of local interest. As before, growers had assistance with experimental set up, assistance as needed during the trial as well as monthly scheduled check-ins, and evaluation. Treatments in all three studies were organized in a completely randomized design (CRD) with 24 replicates (first and third study) or 16 replicates (second study) and data will be analyzed with analysis of variance using a complete factorial of each design. Means will be separated at the 5% level using Tukey’s honest significant difference test.

Objective 2. Cold Hardiness Evaluation

To date, there has not been a comprehensive evaluation of olive cultivars for winter cold hardiness. This is partly due to the large number of named cultivars as well as the relative unimportance of cold injury as a limiting production factor in most traditional growing regions. Studies of cold hardiness done in Mediterranean production areas have compared only a few cultivars in most cases, and are often concerning frost injury to flowers and not tissue injury from low winter temperatures to foliage and stems (Bartolozzi and Fontanazza, 1999).

The cold hardiness evaluation study will involve acquisition of cultivars from domestic sources. The goal is to acquire as many cultivars as possible and to evaluate them for hardiness as well as fruit quality. Inter-institutional and grower cooperation has already begun and various sources of support for this trial are actively participating in the project. The first 29 cultivars were obtained as cuttings in June 2017 from the USDA National Germplasm Repository in Davis, CA. Further cuttings from this collection, the largest olive germplasm collection in North America, were obtained in 2018 and 2019. Grower-cooperators in the Willamette Valley and elsewhere provided a further 60 cultivars in summer 2017. Cuttings of several cultivars were acquired as cuttings from the orchard of Bogdan Caceu near Dallas, OR. Michael Remmick, researcher with Hortifruit in Dayton, OR, provided older age, developed plants in one- through five-gallon sized pots, which were planted in a stock block at NWREC. We also received finished liners of three reputedly very hardy Lebanese cultivars through Olive Grove Partners of Dripping Springs, TX to include in the stock block for re-propagation and inclusion in the evaluation. Cuttings were collected in August 2019 from the established plants in the stock block and all other collected accessions. These cuttings were rooted and grown on in 2020 for a simultaneous planting of all acquired cultivars in the hardiness evaluation in a one acre plot at NWREC established summer 2021. In the future, there is also an opportunity to receive cuttings from the extensive collections of cultivars from the Olive World Collection in Cordoba, Spain. This part has been postponed as it has been logistically challenging to find funds to travel internationally for this purpose. Assuming import quarantine requirements from USDA-APHIS can be met, this offers the possibility of evaluating many previously unavailable cultivars.

Cuttings were prepared and rooted in a greenhouse at NWREC. Three to four-inch cuttings of current-seasons growth were treated with hormone and placed in cell trays in 50:50 peat: perlite under periodic mist.  After rooting, cuttings were grown on in 1 gallon pots and protected through the winter of 2020-21. In July 2021, the young trees were planted out in a 1-acre field planting at NWREC on a Willamette Silt Loam soil. The planting is a completely randomized design with four single-plant replications of each cultivar.  There are a total of 118 accessions in the trial. Trees are spaced 12' apart and the plants are 10' apart within the row. Fertilizer was applied at the time of planting and a microsprinkler system was installed to provide irrigation. Weeds will be managed by installing landscape fabric in the tree rows, as well as by hand weeding and mowing the aisles. Data to be collected starting in 2022 include plant size (height, trunk diameter) at the end of each growing season, flowering (timing, flower number in season) as well as ratings of cold injury in late spring each year. Data will be analyzed then using a factorial on the CRD Contrasts will be used to compare the effect of cultivar on measured variables. Means will be separated at the 5% level using Tukey’s honest significant difference test.

An additional component of this trial,  includes direct farmer participatory research. A datasheet and cold injury rating system was created and compiled to be utilized by area growers to allow them to collect their own cold hardiness and temperature data, using a consistent procedure which can be compiled and compared across sites. Weather data at participating grower locations was monitored with KESTREL/HOBO data loggers installed on-site. Collection of winter injury data from grower sites was not necessary in 2020/21 due to lack of cold injury, low temperatures did not reach damaging levels. The 4 grower sites utilized in 2021/22 will be evaluated in late spring when symptom development is most apparent.  This will provide additional data from an array of locations and enhance knowledge of the performance of individual cultivars in different environments. Once the trees have matured, fruit ripeness and development will be evaluated, depending on changing seasonal weather conditions across years. A collaboration with the Linus Pauling Institute at Oregon State University has been established and is in development, which will include phenolic/anthocyanin and phytochemical content analysis in oil.

Objective 3. Overwintering, up-potting, and field establishment research

Growers in Oregon are looking to diversify their crops in anticipation of future climate conditions. Olives can be used to produce a value-added product that is shelf stable and can generate income by being available for sale throughout the year. Oregon’s climate may provide adequate growing conditions for this developing crop. Existing information on olives focuses on growing them in temperate but warm Mediterranean regions. “The sensitivity to frost reduces the extension of olive cultivation northwards; in the marginal northern limit of olive cultivation, culture is confined to coastal areas” (Therios, 2009). Oregon’s Willamette Valley has a relatively mild climate for a northern latitude, with cool, wet winters and warm, dry summers. This temperate climate, influenced by coastal marine weather, makes the growing conditions within the Valley adequate for production of olives, once the correct cultivars and growing methods are determined. This study aims to evaluate overwintering and up-potting practices to assist with rapid orchard establishment and determine if plant size and maturity at time of planting affects survival and/or susceptibility to winter injury. Overwintering involves moving potted plants to a protected structure in the winter months allowing for protection from winter cold damage and the development of more mature plants. Up-potting is a procedure that transfers an immature plant that has outgrown its initial container into a larger container to accommodate root growth and encourage further development of its trunk and canopy. Combined, these methods may allow growers to produce planting stock that is less susceptible to cold damage once transplanted into the field.

Our up-potting trial will address observations made by growers that larger, more mature olive plants are more resistant to winter cold damage than smaller, younger plants. While trees may be planted directly in the field from their industry standard purchased size (4-to-6-inch planting sleeves or “liners”), this practice is not considered optimal for commercial purposes in Oregon’s climate. This is because the growth rate of the canopy is slower than that of the root system (Fabbri, 2012), which may be particularly detrimental in Oregon as the winters are colder than in other olive growing regions, leading to greater winter injury to young, newly developed branches (Sibbett and Osgood, 2015).

In this study, four cultivars ‘Frantoio’, ‘Leccino’, ‘Ascolano’ and ‘Amphissa’ were evaluated. These have been recommended by local olive growers as more “tolerant to winter cold damage”. Plant size/age to be compared include 4-inch liners, transplanted in a gallon pot for 3 to 6 month period, then transplanted to the field, and 3 and 6-gallon plants up potted from 4-inch liners. Up potted containers were protected in a double-walled greenhouse in the winter for 1 season (3 gallon-sized pots) and 2 seasons (6 gallon-sized pots) to avoid cold injury and encourage additional growth. Back-up heat operated only when night temperatures was forecasted to drop below 25°F, to reduce cost and make it feasible for growers to implement. Optimal stage of development (1 year old/directly from nursery, 2 years old/1 season of growth at NWREC greenhouse, and 3 years old/2 seasons of growth at NWREC greenhouse) for transplanting was evaluated for the different age trees across years. The treatment combinations were arranged in a randomized block split-plot design with ten replicates. Data collected includes trunk diameter at 10 cm above soil level, length of longest shoot, and shoot number for all shoots longer than 5 cm, twice per year, at spring (June) and fall (November). Data was analyzed using analysis of variance and means will be separated at the 5% level using Tukey’s honest significant difference test.

Anecdotally, olive producers in Oregon have had better success on sloped land at a higher elevation than on flatter sites in the Valley. Including sites with both conditions in our research will increase the scope of our findings. The study will be conducted at two sites, NWREC and OSU’s Woodhall Vineyard, the first located on Willamette Valley flat and low elevation land and the second on sloped higher elevation hills toward the coastal range, respectively. Expanding collaboration and interest from managers and researchers at both sites allowed these experiments to expand the scope of research to include for full irrigation for a spring planted crop and irrigation during establishment for fall planted field. Additionally, spring-planted fields will demonstrate use of raised beds with woven weedmat for weed protection, while fall-planted fields will utilize flat beds with rotational cover-cropped aisles.

Objective 4. Disseminate Research Findings

Initial project outreach included a comprehensive survey of all known Oregon olive growers during 2018-2019, to establish baseline industry statistics, document current grower practices, and determine grower needs and research priorities for fine-tuning objectives for this and future funded projects. Survey results have been shared with the research project advisory council and at yearly grower meetings.

During and following research, results will be disseminated via written and video media publications; online platforms, including social media platforms; and in-person meetings. Oregon olive growers will be given yearly research progress reports and will be able to access Oregon olive publications, once the project is concluded; best practices, as determined by these trials; and regularly updated data from other participating growers at a yearly in-person event. Written media publications will continue to be pursued as opportunities arise. To date, the olive research team has been featured in articles in the Capital Ag Press, the Polk County Itemizer-Observer, and the Marion County Extension & 4-H Service District newsletter.

How-to videos were filmed at the conclusion of the project (2021). Filming of the how-to videos was conducted on-farm and showcased propagation practices and up-potting providing visual references for olive growers throughout the state and in similar climates around the world. The videos are posted on the OSU Small Farms Olive website.

We have created an OSU Olea Project website where growers can find our contact information to communicate directly with the researchers as well as find general information about the project. Data from growers will be presented anonymously and include maps of olive cold hardiness results across Oregon, and graphs of the results from the propagation and up-potting trials in our yearly in person meeting. The how-to videos will also be shared via OSU media resources.

Updates on the project will also be disseminated via social media. Anecdotally, olive producers and other small farmers prefer Instagram as a social media platform to share information. At the date of this writing, for example, the Olea Project account which posts exclusively on olive research project updates, workshops and field days, and highlights olive growers in the region, has 223 followers, and all content is cross-posted on the general OSU Small Farms Mid-Willamette Valley Instagram account, which has 1026 followers. Additionally, Instagram is the primary social media outlet for multiple collaborators. Posts on both the Olea Project account and OSU Small Farms account about the olive project have yielded positive responses as well as support from other organizations.

In-person meetings have included annual meetings with our advisory council and growers, Extension workshops, and olive field days. Updates on the research projects have been given at regional presentations such as the OSU Small Farms Conference, Small Farm School, and other venues in the region. Beginning in the third year, Extension workshops were hosted to demonstrate best practices (postponed due to COVID, see below for more discussion). In the final year (2021), a two day olive workshop was held on April 22-23. The first workshop days included farm tours and presenters from the Olea project and UC Davis. In 2022 a grower meeting and research update was given at a grower site in February.

Research results and discussion:
  1. Olive propagation techniques for Oregon

The second year of propagation trials involved the replication of the 2018 timing/hormone trial and completing the substrate/cultivar trial.  In repeating the timing/hormone trial, rooting hormones at two different rates were used (IBA and IBA + NAA) to root ‘Arbequina’ olives during three timings (May, July, October).  After 90 days the spring and summer timings were evaluated by determining percentage rooted and root number and length. 

In the substrate trial, two different cultivars were used, ‘Leccino’ (high rooting capability) and ‘Picual’ (medium rooting capability).  Both of these cultivars were propagated at a grower site and at NWREC with 4 different rooting substrates which were varying combinations of coir: perlite and peat: perlite. After 120 days the percent rooted, root number and length were measured.

A second grower site was initiated in fall 2019.  This site is currently evaluating a “low input” scenario, for growers who want to root some of their own cuttings without building a greenhouse or mist system.  A preliminary trial at NWREC in fall 2018 used clear plastic domes placed over flats of cuttings on a heat mat to maintain humidity for olive cuttings, rather than a mist system.  High rooting success encouraged our second collaborator to build an open window structure against a building which is south facing.  This structure has bottom heat, however the space will only receive additional ambient heat during extreme cold spells.  The success rooting, number and length of roots for the NWREC were evaluated in January 2020 and additional analysis is needed for the grower results.

A third grower (commercial nursery) asked to be added to our propagation trial, to evaluate our techniques and methods to improve their current protocols for larger scale production. Following our same protocols in larger trays they have achieved high rooting success and automation of the system with minimum supervision in the fall. We will continue to collaborate with this grower and data will be collected and a analyzed to evaluate his fall 2019 results as his 2020 spring and summer trials were cancelled due to the pandemic. The grower will communicate to us if they decide to continue further evaluations when regular operations resume, but this may be past the time of the grant extension request.   

First Study – Timing/hormone

For the 1st study, timing/hormone, the two years of studies were analyzed for both locations, the grower site and the NWREC site. For both sites, rooting of the Arbequina olives was overall successful, with some differences seen for timing and hormone rates.  In 2018, at the grower’s site, overall, the highest number and longest roots on average were seen in fall at 8, and 50cm, respectively using the “2D” hormone.  This treatment also produced the highest rooting percentage during fall of 88% success, however, “3H” in the summer had 92% rooting success, which was significantly higher than the other treatments.  At NWREC the highest primary root number (13) occurred in the spring, root length was not significantly different for hormone, but was longest in the spring (52cm).  Rooting percentages varied between 58% and 96% with the 96% rooting occurring in spring with the “2D” and “8H” hormones.

This study was repeated in 2019 at both sites.  In 2019 at the grower site, the highest average number of primary roots (12), and average longest roots (57cm) was in the spring using “8H” hormone treatment.  Rooting percentage was also significantly highest in the spring at 81%.  At NWREC, a power outage in the greenhouse in late May required re-sticking of the spring cuttings two weeks after the original sticking date which was May 16th.  This later date appears to be less optimal due to the lower average rooting seen from this data set (65%).  As a result, the summer treatment had the highest average root number (4) and root length (32cm) and 76% success rooting, however the spring “3H” treatment also fared well with an average of 4 primary roots, 35mm total root length and 75% rooting percentage.

After evaluating both locations during all seasons it was decided to use a mid-May sticking date with the 3H hormone for the 2nd year media/cultivar study and the 3rd year compilation study.

In a separate side study which aimed to examine if growers without mist systems would be able to propagate cuttings successfully on a small scale, we repeated the above timing/hormone study in fall without mist, covering the trays of plants with clear plastic domes. This was done at NWREC in 2018 and 2019, and is currently underway at a grower site in Yamhill, OR, in an outdoor structure with south-facing windows. The grant provided heat mats, trays, media and rooting hormone for this small-scale olive grower to propagate their Arbequina olives. The Yamhill site was stuck in October 2020 and will be evaluated in February 2021.

The non-misted olives grown at NWREC had a strong rooting success rate (72%), which was not statistically different from those cuttings grown under mist (69%). For both methods, the average number of primary roots was 4, and the average root length was 19cm. This trial has shown that a low-input site can be used to propagate cuttings in the fall with high success.

Second Study – Media Trial

The 2nd study, the media trial, was completed in 2019 and 2020. This study looked at varieties with different rooting abilities, ‘Leccino’ (high) and ‘Picual’ (medium), and propagated them in 4 media combinations.  This study was completed both years at a grower site in Dayton, Oregon and at NWREC.

Both sites had consistent results regarding the media and cultivar results, however here we will discuss in more detail the grower site in Dayton. ‘Picual’ rooted at 64% and ‘Leccino’ at 56%, although the differences were not significant (see Table 1). However, the number of primary roots for ‘Picual’ was significantly greater at 6, in comparison to 3 for ‘Leccino’.  The total root length was not significantly different between ‘Leccino’ and ‘Picual’, but there was a cultivar by year interaction that requires further analysis. In 2019 rooting was significantly greater in Dayton with 68% of the cuttings rooting compared to 52% in 2020.

When looking at substrate rate, the percent cuttings rooted was 70%, 63%, 59% and 48% for Peat:Perlite 1:1, Peat:Perlite 3:7, Coir:Perlite 1:1 and Coir:Perlite 3:7, respectively; however these differences were not significant.  Significant differences were seen for both root length and root number. Cuttings rooted in the Peat:Perlite 1:1 media had highest root number and root length.  The substrate with the comparatively lowest root number and length was the Coir:Perlite 3:7, and it therefore would not be recommended to use this media for rooting olives.  The data from this trial allowed us to determine the Peat:Perlite 1:1 media as the most successful, and utilize these components and rates for the 2020 compilation trial.

Third Study – Compilation trial

The compilation study aimed to combine the previous studies, using the timing which was most successful in the first study (mid-May), the media which was most successful in the second study (Peat:Perlite 1:1), and the best two rooting hormones (3H and 2D). ‘Leccino’ and ‘Picual’ were once again chosen as the varieties due to their common use by olive growers and their positive qualities in our region. This trial was completed at both NWREC and a grower site in Dayton.

When comparing the two sites, cuttings performed better at NWREC overall (Table 2). In general, this was seen in the other studies as well, but it was directly analyzed in this study.  Both sites had a similar set up with bottom heat set at 72⁰F, heated greenhouses with similar temperature settings, and a mist system with Netafim Coolnet fogging nozzles. However, daily mist clock settings, overall irrigation, and grower experience would be different at the two sites, therefore it is likely that at least some of the differences in cutting success and growth could be attributed to human influence.

As in the 2nd study, ‘Picual’ had a greater root number and length of 5 and 26cm, respectively.  For rooting percentage, there was an interaction between the hormone and the cultivar, with ‘Leccino’ grown with 2D hormone having a significantly higher rooting percentage (75%), in comparison to 3H (25%). This difference was not significant with ‘Picual’, which rooted at 81% with 2D, in comparison to 65% with the 3H rate of hormone. Overall, when looking at both olive varieties together, the hormone 2D had a significantly greater number of roots (4) as well as longer roots (24cm) when compared to 3H (at 2 and 15cm, respectively).

After analyzing data from the compilation trial, the hormone rate “2D” was found to produce the highest number of roots and longest roots for ‘Leccino’ and ‘Picual’ olive varieties.  From the media trial, Peat:Perlite 1:1 was the most successful media for rooting ‘Leccino’ and ‘Picual’. Based on the 1st study with ‘Arbequina’ olives, Mid-May was the best timing to take and propagate cuttings when a mist system is present. These recommendations would be a good starting place for growers looking to begin propagating their own olives.  However, there may be some variability with different varieties, and further research will be needed, especially as our research continues and we are able to examine the cold-hardiness field trial.

PLEASE SEE ATTACHED MEDIA (Propagation Addendum) FOR ADDITIONAL REFERENCE

WSARE Report Propagation Addendum

2. Cold hardiness of olive cultivars

The cold hardiness project consists of two separate components: a forthcoming field evaluation of most olive cultivars currently available in North America, planted at the OSU North Willamette Research and Extension Center (NWREC) in Aurora, OR and a corresponding effort to collect data on cold injury to cultivars currently planted in grower orchards in western Oregon. 

Field Evaluation: Olive cultivars have been obtained as cuttings through annual requests to the USDA National Clonal Germplasm Repository (NCGR) in Davis. CA, which is the only repository of olive cultivars in North America and holds approximately 123 olive accession. These requests are limited to 30 accessions per year per NCGR policies, therefore acquisition of the available cultivars must occur over more than one year. 

Olives are thought, through anecdotal data, to increase in hardiness with plant age. As a result, all cultivars to be planted in the field evaluation must be propagated at the same time.  To satisfy this requirement, germplasm requests were made to NCGR in 2017, 2018 and 2019. Cultivars rooted from these requests were potted and were grown on at NWREC. These cuttings were stuck at NWREC and at this point all accessions held at NCGR Davis should be in our possession. We also received a donation of some mature plants from a local source, which were planted out at NWREC in a stock block in August, 2018 and were grown on for cutting collection in 2019.  

Cuttings of the last of the NCGR Davis accessions were received and stuck at NWREC in July, 2019. In mid-August, cuttings were taken from all stock block accessions as well as potted plants from prior NCGR Davis acquisitions. Cuttings were treated with 3000ppm IBA and stuck in a 50:50 mix of peat:perlite in 4” deep square Anderson trays on bottom heat and under mist in the NWREC greenhouse. A total of 152 accessions were stuck in 2019 for rooting and growing on in 2020 for the cold hardiness evaluation. 

Cuttings were potted into 4” band pots in spring 2020 and then up-potted to 1-gallon containers in late summer 2020 and grown on in a covered hoophouse in winter 2020-21. The field evaluation of all accessions rooted in sufficient quantity (n=4) were planted at NWREC in 2021. An inventory taken in December 2020 showed 92 accessions for which there were at least 4 plants available and an additional 9 accessions for which 3 plants each were available for the field evaluation.

Although the stock block is not a research evaluation in itself, as of the ~60-70 cultivars planted in there, plant age varies significantly and most are represented by only 2 individual plants and some by only one, it is still a fairly diverse collection and so some data were collected on vigor, flowering and fruit set on this collection in July 2020. This was followed up by harvesting fruit from the trees in October 2020.

Vigor of stock block plants were assessed by relative length and abundance of current season growth on a 1-5 scale. In general, the plants in the stock block show good vigor in the soils and climate of the Willamette Valley, an observation which is similar to other Mediterranean-climate plants grown in the region and attributable to relatively fertile soil and abundant moisture.

Flowering was assessed by observing the relative abundance of flowers present on the previous-season growth and rated on a 1-5 scale. This characteristic varied widely among the various cultivars in the stock block, possibly influenced by differing ages and hence precociousness of the plants. Some cultivars clearly flowered more heavily than others, including ‘Aglandau’, ‘Amphissa’, ‘Arbosana’, ‘Balkan’, ‘Chemlali’, ‘Coratina’, ‘Koroneiki’, ‘Mixan’, ‘Redding-Picholine’ and ‘Tragolea’.

The data on fruit set involved assessing on a 1-5 scale the relative percentage of flowers that had produced viable fruit. This was quite revealing as a relatively few number of the cultivars which had exhibited good flowering also exhibited high fruit set. Cultivars which did show relatively high fruit set included ‘Arbosana’, ‘Carboncella’, ‘Mixan’ and ‘Tragolea’.

These data were followed up by harvest in October and only a few of the cultivars produced significant amounts of fruit. Again this is probably partly due to the variation in plant age. Simply using a yield of 1 pound of fruit per plant as a benchmark, those cultivars that achieved this include ‘Arbosana’, ‘Bouteillan’, ‘Canino’, ‘Carboncella’, ‘Coratina’, ‘Frantoio’, ‘Lucca’, ‘Mixan’ and ‘Taggiasca’. Since some of these did not rate highly in earlier observations of flowering or fruit set, there may be some compensation in fruit size and weight or other factors at work. These observational data certainly show a complicated interaction of vigor, flowering, fruit set and fruit size, as well as other factors in determining yield of olives in the Willamette Valley.

As the trees in the cold-hardiness field planted in July 2021 are further established, similar data to those collected from the stock block and reported above will be collected starting in spring/summer 2022.

Cold Injury in Established Orchards: The effort to document cold injury to olive cultivars at grower sites includes 6 collaborator farms in the Willamette Valley and one in the Umpqua Valley. It also includes one greenhouse in the Willamette Valley. A total of 11 weather sensors (ONSET® HOBO® and Kestrel® DROP®) were installed at these sites in fall 2018/winter 2019, 2019/2020, 2020/2021 and 2021/2022. Temperature data will be collected from these sites throughout the winter season and correlated to evaluations of cold injury to cultivars undertaken in late spring each year. Four weather sensors were also installed at our own research sites at NWREC and Woodhall Vineyard in Alpine, OR for the same purpose. Additional weather data is available from Bureau of Reclamation AGRIMET weather stations in Aurora, Corvallis, Forest Grove and Roseburg. An AGRIMENT weather station was installed at the Woodhall Vineyard/Alpine site in summer 2020. As a further component of this effort, a review of available literature on cold hardiness of olive was conducted which included a survey of various methods of assessing cold injury to woody plants.

Fortunately for growers but unfortunately for research purposes, the winters of 2018-2019, 2019-2020, and 2020-2021 were mild and when we conducted the spring evaluation we saw little to no freezing damage or winter cold injury at any site. Data analyzed presented zero mortality and a minimal damage in very few sections of tissue at limited sites. This showed that in “mild” winter years, damage can be reduced to a minimum in already established orchards.

PLEASE SEE ATTACHED MEDIA (Cold Hardiness Addendum) FOR ADDITIONAL REFERENCE

WSARE Report Cold Hardiness Addendum

WSARE Cold Hardiness Addendum 2022

3. Overwintering, up-potting, and field establishment research

In 2020 we received our final shipment of over 400 trees from the nursery supplying research plants, including the third batch of plants for experimental plots, as well as the remainder of additional pollinizer trees. Trees were transplanted to 1-gallon pots. 80 of these 1-gallon trees were planted in the two spring-planted fields at NWREC and Woodhall, completing the experimental plots at both sites in May. 120 trees, including 1-gallon, 3-gallon, and 6-gallon sized plants, were planted in the fall-planted fields at both sites in October. At the same time, all remaining experimental potted plants were transplanted to the next largest pot size, and moved to the winter greenhouse as in previous years.

Data was collected in spring and in fall, shortly after each planting. This was the first year that any significant fruit set was seen in the fields, and a small initial harvest was conducted in early November. Few to no trees have been lost in the winter due to cold damage, though some tree losses have occurred post-transplant (spring-planted fields) or mid-summer (fall-planted fields), and we are continuing to learn about ways to reduce these losses.

Changes in response variables (shoot number, length of longest shoot, and trunk diameter at 10 cm above soil surface) were calculated for single growing seasons, taking the difference of end of season (fall) measurements minus start of season/time of planting (spring) measurements for spring-planted trials, and end of season (fall) measurements minus time of planting (fall) measurements for fall-planted trials. Tree mortality has also been tracked.

Trees planted in Fall 2018/Spring 2019 at NWREC had a greater increase in shoot number and trunk diameter compared to trees planted in Fall 2019/Spring 2020). In general, fall-planted trees had greater shoot numbers and trunk diameter compared to spring-planted trees. ‘Leccino’ had the greatest shoot number, ‘Amphissa’ had the lowest, while ‘Frantoio’ and ‘Ascolano’ shoot numbers were not different from ‘Leccino’ or ‘Amphissa’. The impact of planting year on shoot length varied depending on production system, with 2018/2019 spring-planted trees having twice the shoot length of 2019/2020 spring-planted trees, and four times the shoot length of both fall-planted sets of trees. Spring-planted ‘Leccino’, ‘Frantoio’, and ‘Ascolano’ had the greatest shoot length, and were not different from spring-planted ‘Amphissa’, which itself was not different from fall-planted ‘Amphissa’ and ‘Ascolano’, while fall-planted ‘Frantoio’ and ‘Leccino’ had the shortest shoot lengths. Shoot length and trunk diameter were impacted by the interaction of planting year and cultivar. All cultivars planted in 2018/2019 as well as 2019/2020 ‘Ascolano’ had greater shoot lengths, compared to 2019/2020 ‘Amphissa’ and ‘Frantoio’, while 2019/2020 ‘Leccino’ was not different from the highest and lowest values. 2018/2019 ‘Amphissa’, ‘Frantoio’, and ‘Leccino’ had the greatest trunk diameters, with 2018/2019 ‘Ascolano’ and 2019/2020 ‘Amphissa’ having the smallest trunk diameters, and 2019/2020 ‘Ascolano’, ‘Frantoio’, and ‘Leccino’ not different from the lowest values. 

Across two growing seasons, ‘Frantoio’ and ‘Leccino’ had the greatest shoot at 216 and 204 respectively, with ‘Amphissa’ at 102 and ‘Ascolano’ at 141, half and nearly half the shoot number of other cultivars, respectively. The interaction between cultivar and production system persisted throughout two growing seasons, with spring-planted ‘Leccino’, ‘Amphissa’, and ‘Leccino’ having the greatest shoot lengths, spring-planted ‘Ascolano’ not different from spring-planted ‘Amphissa’ and ‘Leccino’, and all fall-planted cultivars with the shortest lengths, ranging from 13-21 cm. Similar to year two, ‘Frantoio’, ‘Leccino’, and ‘Amphissa’ had the greatest trunk diameters, all higher than ‘Ascolano’ which was nearly half that of ‘Leccino’.

Spring-planted trees at NWREC showed higher survival rates as of Fall 2020 at 99%, compared to fall-planted trees at 91%. This includes trees planted during the 2018/2019 and 2019/2020 seasons, with no difference between the years. While temperatures did not drop low enough during any part of the experiment for trees to experience mortality, observations suggested that fall-planting was associated with higher levels of tip die-back than with spring-planting.

At NWREC there was no difference in survival rate for trees planted at 1.5 years of age, compared to trees planted at 2.5 years, with each averaging 95% survival as of Fall 2020. Cultivar also was not found to affect survival rates for trees planted at 1.5 years of age in 2018 and 2019.

At Woodhall, trees planted at 1.5 years of age had nearly twice the number of shoots compared to those planted at 2.5 years of age. ‘Frantoio’ and ‘Ascolano’ had the greatest shoot numbers, with ‘Ascolano’ not different from ‘Amphissa’ and ‘Leccino’. Trees planted at the younger age had eight times the shoot length of those planted at 2.5 years of age. ‘Frantoio’, ‘Leccino’, and ‘Amphissa’ had the greatest trunk diameters, with ‘Ascolano’ not different from ‘Leccino’ and ‘Amphissa’. Trees planted at 1.5 years of age had lower survival rates as of Fall 2020, compared to trees planted at 2.5 years of age. There were no differences based on cultivar in survival rates for trees planted at 1.5 years of age in 2018 and 2019, with trees of different planting years analyzed separately.

This study demonstrates how, barring extreme winter cold events over the first three years, olive orchards may be successfully established with multiple cultivars in Oregon’s climate. Results show how spring-planting may be preferable to fall-planting, and the importance of establishment irrigation. Without the ability to test the hypothesis of older, larger trees showing better establishment than smaller, younger trees, we are not able to say if up-potting and overwintering gives an advantage, as high amounts of vegetative growth were seen in trees transplanted at both sizes and ages. Across both sites, production systems, and multiple years, ‘Leccino’, ‘Frantoio’, and to a slight lesser extent ‘Amphissa’ show increased growth compared to ‘Ascolano’, suggesting that these cultivars seen widely as too vigorous for super-high or high-density plantings in other regions, may be more well-adapted to growing in a climate such as Oregon’s.

PLEASE SEE ATTACHED MEDIA (Up-Pot Addendum) FOR ADDITIONAL REFERENCE

WSARE Report Up-Pot Addendum 2022

4. Outreach

2020 opened with three successful outreach events. The first was an Olive Oil Analysis event held in collaboration with OSU’s Linus Pauling Institute. This event featured speakers from the Olea research team, Linus Pauling Institute staff discussing options for oil analysis for phenolic content and other compounds of interest, as well as Paul Durant from the Oregon Olive Mill. The workshop included an Oregon olive oil tasting, and tour of the lab facilities. The second was the Culinary Breeding Showcase, where the research team hosted a tasting table for multiple grower collaborators as in previous years. The final event before COVID was a presentation at the 2020 OSU Small Farms Conference, again with over 40 people in attendance.

The arrival of COVID-19 severely impacted plans for outreach events intended for the final year of the project. However, the research team quickly adapted, and began hosting a series of Instagram live workshops on the social media platform. These sessions included a virtual class on pruning potted olives (April), and a webinar and virtual class covering on-farm olive propagation (May). Each session was attended by upwards of 20-40 people and allowed the research team to continue building connections and sharing research findings and best practices with perhaps an even wider audience than could be accomplished with traditional in-person events. This initiative led to the research team being presented with one of OSU’s “Stay at Home Hero” awards, for continued dedication to research and serving the community during the pandemic.

2020's Advisory Council and Olive Grower Meeting was held as a virtual event, with similar numbers of attendees as in years past (between 30 and 50.) Once again, the virtual nature of the event allowed prospective growers from outside the Willamette Valley, and as far as away as southern Oregon, to easily attend the event and network with other growers, which may not have been possible had the event been held in-person.

Other virtual events included multiple presentations at the American Society for Horticultural Science annual conference, focused on findings from the 2018-2019 Oregon Olive Grower Needs Assessment and Survey, and a presentation covering initial considerations for small olive orchard establishment. This presentation was given as part of the eOrganic student article contest, in which an article on practical lessons from the olive research project was submitted, and selected as one of the winning entries. This also resulted in a publication on the eOrganic website, authored by all members of the research team (http://eorganic.org/node/34189, see below).

Initial Considerations Olive Orchards PNW_ eOrganic

The final virtual event of 2020 was a meeting discussing a potential Oregon Olive Growers Association which occurred in October. This event drew a number of experienced and prospective growers who are seeking to further develop the olive industry in Oregon. The OSU Olea project has been invited to have a permanent seat to further research efforts by the potential association.

In April 2021 a two-day field event and tour was hosted at two separate grower sites and at NWREC. The growers gave tours of their olive operations as well as an olive mill. Experienced California olive oil producers (Bondolio) came to NWREC and discussed their olive oil marketing strategies. Louise Ferguson and Dan Flynn from UC Davis also presented at the event, providing expertise about managing olives.  The Olea team gave research updates as well as tours of the various projects as part of this grant -propagation, up potting, and cold hardiness. Forty individuals attended the event, however registration was limited due to COVID restrictions.

In February 2022 a meeting was held with olive growers to discuss an Oregon olive grower's group as well as Olea research updates. Twenty-three growers were in attendance.

Other outreach updates include the transition to a permanent webpage on the OSU Small Farms website (https://smallfarms.oregonstate.edu/smallfarms/olive-research-oregon), and the creation of the olive-specific Instagram account (@oregonolives) used in the first months of the pandemic and beyond to reach growers and visually showcase olive trials and grower sites.

PLEASE SEE ATTACHED MEDIA (Outreach Addendum) FOR ADDITIONAL REFERENCE

WSARE Report Outreach Addendum

Outreach addendum 2022

Research conclusions:

For the propagation study, after analyzing data from the compilation trial, the hormone rate “2D” was found to produce the highest number of roots and longest roots for ‘Leccino’ and ‘Picual’ olive varieties.  From the media trial, Peat:Perlite 1:1 was the most successful media for rooting ‘Leccino’ and ‘Picual’. Based on the 1st study with ‘Arbequina’ olives, Mid-May was the best timing to take and propagate cuttings when a mist system is present. These recommendations would be a good starting place for growers looking to begin propagating their own olives.  However, there may be some variability with different varieties, and further research will be needed, especially as our research continues and we are able to examine the cold-hardiness field trial.

The cold hardiness research plot is established and will be continuing beyond the timeline of this grant. The 114 replicated olive accessions have all survived their first winter and will be evaluated for cold hardiness, growth and harvest in the future providing necessary information to olive growers regarding the optimal cultivars to plant in the maritime Pacific Northwest.

This up potting study demonstrated how, barring extreme winter cold events over the first three years, olive orchards may be successfully established with multiple cultivars in Oregon’s climate. Results show how spring-planting may be preferable to fall-planting, and the importance of establishment irrigation. Without the ability to test the hypothesis of older, larger trees showing better establishment than smaller, younger trees, we are not able to say if up-potting and overwintering gives an advantage, as high amounts of vegetative growth were seen in trees transplanted at both sizes and ages. Across both sites, production systems, and multiple years, ‘Leccino’, ‘Frantoio’, and to a slight lesser extent ‘Amphissa’ show increased growth compared to ‘Ascolano’, suggesting that these cultivars seen widely as too vigorous for super-high or high-density plantings in other regions, may be more well-adapted to growing in a climate such as Oregon’s.

Participation Summary
12 Farmers participating in research

Education

Educational approach:

During and following research, results were disseminated via written and video media publications; online platforms, including social media platforms; and in-person meetings. Oregon olive growers were given yearly research progress reports and will be able to access Oregon olive publications. Written media publications will continue to be pursued as opportunities arise. To date, the olive research team has been featured in articles in the Capital Ag Press, the Polk County Itemizer-Observer, and the Marion County Extension & 4-H Service District newsletter.

How-to videos were filmed at the conclusion of the project (2021). Filming of the how-to videos were conducted on-farm and showcases propagation practices, and up-potting providing visual references for olive growers throughout the state and in similar climates around the world. The videos are hosted on the OSU Small Farms Olive page, see Scholarly Publications and Educational Materials below.

We have also created an OSU Olea Project website where growers can find our contact information to communicate directly with the researchers as well as find general information about the project. Data from growers will be presented anonymously and include maps of olive cold hardiness results across Oregon, and graphs of the results from the propagation and up-potting trials in our yearly in person meeting. The how-to videos are also shared on the website.

Updates on the project will also be disseminated via social media. Anecdotally, olive producers and other small farmers prefer Instagram as a social media platform to share information. At the date of this writing, for example, the Olea Project account which posts exclusively on olive research project updates, workshops and field days, and highlights olive growers in the region, has 331 followers, and all content is cross-posted on the general OSU Small Farms Mid-Willamette Valley Instagram account, which has 1026 followers. Additionally, Instagram is the primary social media outlet for multiple collaborators. Posts on both the Olea Project account and OSU Small Farms account about the olive project have yielded positive responses as well as support from other organizations.

In-person meetings included annual meetings with our advisory council and growers, Extension workshops, and olive field days. Updates on the research projects were given at regional presentations such as the OSU Small Farms Conference, Small Farm School, and other venues in the region. Extension workshops were hosted to demonstrate best practices.

Producer & Ag Professional Educational Activities

Research updates will and have been provided to the advisory council and a larger public meeting of all interested current and prospective growers on a yearly basis. Annual ‘Olive Field Day’ events will and have been hosted at the research site(s) as an educational opportunity for growers to learn the practical application of the olive research as well as a forum to share findings and development in the research. Growers participating in on-farm trials, including propagation, and overwintering and up-potting trials, will also share updates and results from their trials. Additional workshops on specific topics have and will continue to be hosted in response to grower interest. Updates on the research projects also took place at the OSU Small Farms Conference, Small Farm School, and other venues in the region. Field days, workshops, tours, and advisory council and grower meetings are promoted and communicated via an email list of olive growers, and announced at advisory council/grower meetings. Additional new and prospective growers are continually invited to join the email list when they reach out for consultations and via the Mid-Willamette Valley Small Farms team newsletter mailing and website.

Scholarly Publications & Educational Materials

Publications included trade publications such as Small Farms News, Capitol Press (see 2020 “Oil of Olea” publication referenced below), and Western Farmer-Stockman, OSU Extension publications and peer-reviewed as well as refereed publications. Data from early experiments has been presented in ASHS meetings in 2018, 2019, and 2020, as well as other national and international horticulture events and conferences. An initial publication on considerations for small organic olive orchard establishment in the Pacific Northwest west of the Cascades was published in eOrganic in January 2021.  Research updates and photos have been posted in our Instagram accounts. Five how-to videos on best practices for growing olives in Oregon, were filmed and are hosted on the site at https://agsci.oregonstate.edu/smallfarms/videos-resources. Topics include general propagation, materials for propagation, taking and maintaining olive cuttings, and up potting. Proper citation of Western SARE in all materials produced from this proposal were be observed.

Evaluation and Producer Adoption

To evaluate changes in producers’ knowledge, skills, attitudes, and awareness, a comprehensive pre-trial survey was issued to growers in 2018 specific to current propagation, transplanting/up-potting/field establishment practices, and knowledge of cold hardy cultivars. Propagation practices surveyed included propagation method (by cuttings or other means), cutting collection timing, and use of mist or no mist. transplanting/up-potting/field establishment practices included in the survey consisted of plant sourcing, cultivars grown, plant size and maturity at planting, as well as planting location, fertilization and irrigation techniques and time of planting during the year. Cold hardiness of current plantings will be observed as part of the on-farm grower trials. Multiple growers have already stated to our team that practices have improved greatly (rooting rates and planting time), which indicates a great success in early adoption of practices.

Educational & Outreach Activities

149 Consultations
8 Curricula, factsheets or educational tools
4 Journal articles
35 On-farm demonstrations
2 Online trainings
15 Published press articles, newsletters
42 Tours
30 Webinars / talks / presentations
4 Workshop field days
1 Other educational activities: Olive Oil Analysis workshop in collaboration with the Linus Pauling Institute.

Participation Summary:

175 Farmers
25 Ag professionals participated
Education/outreach description:

Down at the farm article

Oil Analysis Workshop 2019 v4

Small Farms Conference Olive Poster

Olive Growers Meeting flyer

2018-4_OregonWinePress_Oregons Growing Olives

2018-5_Digger_Are Olives Viable Oregon

2018-5_Oregonian_Yes You Can Grow Olives

2019-5_Olive Oil Times_Oregon Project Aims Promote

2019-10_Epicurious_Great Olive Oil Comes From... Oregon

2019-12_TheExpress_The research behind the horticulture industry

2020-3_Capital Press_Oil of Olea

2020-04_CFGrower_Olive productions grows in Oregon

2020-9_Oregon Ag Progress_Pressing Forward Budding Olive

Up-Potting Handout Fall 2019

Survey Handout Fall 2019

Propagation Handout Fall 2019

Cold Hardiness Handout Fall 2019

In 2019, we had our second grower/advisory council meetings taking place at the OSU extension Marion county offices. Input and collaborations were obtained and discussed to continue to move forward with the collaborative research at grower sites. We have presented preliminary data on the propagation trials at ASHS annual meeting as well as continue to outreach to more growers interested in learning more about the project. We’ve participated in various meeting where we’ve presented the progress of the project and answered basic questions about our goals and possible outcomes including: Extension Annual Conference, Durant Olive Fall Festival, Olive Master Class at UC Davis, Small Farms Conference and Linus Pauling Institute. Additional outreach will be conducted in the future as planned. 

In mid-2019 we hosted an Olive Field Tour at the North Willamette Research and Extension Center. We have presented preliminary data on the propagation and up-potting trials and an update on the cultivar evaluation. Over 50 participants joined us for a tour of the greenhouse and field trials. We continue to conduct outreach to more growers interested in learning about the project. We’ve participated in various meeting where we’ve presented the progress of the project and answered basic questions about our goals and possible outcomes including: Extension Annual Conference, Durant Olive Fall Festival, Olive Master Class at UC Davis, Ag West Trade Show. Additional outreach will be conducted in the future as planned. 

2020 opened with three successful outreach events. The first was an Olive Oil Analysis event held in collaboration with OSU’s Linus Pauling Center. This event featured speakers from the Olea research team, Linus Pauling Center staff discussing options for oil analysis for phenolic content and other compounds of interest, as well as Paul Durant from the Oregon Olive Mill. The event concluded with an oil tasting, and tour of the center lab facilities. The second event was the Culinary Breeding Showcase, where the research team hosted a tasting table for multiple grower collaborators. The final event was a presentation at the 2020 OSU Small Farms Conference, again with over 40 people in attendance.

The arrival of COVID-19 severely impacted plans for outreach events intended for the final year of the project. However, the research team quickly adapted, and began hosting a series of Instagram live workshops on the social media platform. These sessions included a virtual class on pruning potted olives (April), and a webinar and virtual class covering on-farm olive propagation (May). Each session was attended by upwards of 15-20 people, and allowed the research team to continue building connections and sharing research findings and best practices with perhaps an even wider audience than could be accomplished with traditional in-person events. This initiative led to the research team being awarded one of OSU’s “Stay at Home Hero” awards, for continued dedication to research and serving the community during the pandemic.

2020's Advisory Council and Olive Grower Meeting was held as a virtual event, with similar numbers of attendees as in years past (between 30 and 50.) Once again, the virtual nature of the event allowed prospective growers from outside the Willamette Valley, and as far as away as southern Oregon, to easily attend the event and network with other growers, which may not have been possible had the event been held in-person.

Other virtual events included multiple presentations at the American Society for Horticultural Science annual conference, focused on findings from the 2018-2019 Oregon Olive Grower Needs Assessment and Survey, and a presentation covering initial considerations for small olive orchard establishment. This presentation was given as part of the eOrganic student article contest, in which an article on practical lessons from the olive research project was submitted, and selected as one of the winning entries. This also resulted in a publication on the eOrganic website, authored by all members of the research team (http://eorganic.org/node/34189).

The final virtual event of 2020  was the inaugural meeting of the newly formed Oregon Olive Growers Association in October, formed by project collaborators with the support of the olea project research team. This event drew a number of experienced and prospective growers who are seeking to further develop the olive industry in Oregon.

In May 2021 a two-day field event and tour was hosted at two olive grower's sites and at NWREC. The growers gave tours of their olive operations as well as an olive mill for producing olive oil. Experienced California olive oil producers (Bondolio) were invited to NWREC and discussed their olive oil marketing strategies and did an olive oil tasting. An additional local olive farmer and collaborator, Marni Redding also gave a tasting of her olive oils. Louise Ferguson and Dan Flynn from UC Davis also presented at the event, providing expertise about growing olives.  The Olea team gave research updates as well as tours highlighting the grant objectives -propagation, up potting and cold hardiness. Forty individuals attended the event, however registration was limited due to COVID restrictions.

Other outreach updates include the transition to a permanent webpage on the OSU Small Farms website (https://smallfarms.oregonstate.edu/smallfarms/olive-research-oregon), and the creation of the olive-specific Instagram account (@oregonolives) used in the first months of the pandemic and beyond to reach growers and visually showcase olive trials and grower sites.

A website to provide updates on research, share information on growing olives, and house upcoming event information was created, though is still in development. In addition, an Instagram account (@oregonolives) has been created to reach growers and visually showcase olive trials and grower sites.

Learning Outcomes

20 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas taught:
  • Olive propagation Techniques
  • Winter protection and up-potting
  • Planning for site selection and project evaluation
  • Field Preparation, Irrigation, Fertilization
Key changes:
  • Farmers participating in this part of the research informed that the knowledge gain in regards to techniques had increased in particular related to plant watering, systems used, media, hormone types and technology to adapt and used in the greenhouse. Three growers collaborated with us for the propagation study during 2019. The hormone study was repeated with both collaborators and one collaborator participated in the substrate study. Both collaborations have led to an increase in knowledge regarding propagation techniques. Changes in techniques have occurred as well as improved success of rooting olive cuttings.

  • Multiple new growers (approximately 6) have determined that using up-potting techniques and keeping plants in pots, have made it easy to protect from cold damage as well as given them more time for root development and planning the orchard in general.

  • 3 growers preparing their projects, have begun to evaluate their site conditions for cold pockets, temperatures and sun exposure prior to planting. Some even getting their own weather stations to reduce possible impact of winter injury and damage and to historically know what happens in the winter at their sites.

  • Growers with no experience in Olive or tree fruit production have evaluated their field planting irrigation and determined their water availability for establishment based on our success and also plant loss without irrigation. Multiple growers also asked the Olea project about field preparation and cover cropping prior to planting.

Project Outcomes

10 Farmers changed or adopted a practice
30 Farmers intend/plan to change their practice(s)
7 Grants received that built upon this project
10 New working collaborations
Project outcomes:

To the date, the following are the current outcomes for all project objectives:

  1. Olive propagation techniques for Oregon

Propagation studies finished in 2020.  Results from the propagation studies show distinct differences from different hormone rates and substrate types. Personal communication with our propagation growers/collaborators has indicated that the rooting percentage achieved during the olive propagation trials are greatly improved compared to their prior propagation results. They have changed their propagation techniques including rooting hormones and propagation media to reflect those which were most successful in the studies. Multiple additional growers have started propagating their own plants and some have expressed interest in starting olive nurseries in order to address the need of locally produced olive trees.

Olive propagation trials have been presented at the American Society of Horticultural Science annual meetings in 2018 and 2019, see citations below:

Barker, T., H. Stoven and J. Fernadez-Salvador. 2018. Cultivar and Growing Media Affect Root Length and Number during Fall Olive Propagation in Oregon.

Barker, T., J. Fernandez-Salvador, and H. Stoven. 2019. Impact of Season and Rooting Hormone Rate on Root Number and Length for Propagated Olive Cuttings in Oregon.

  1. Cold hardiness of olive cultivars

The one acre collection of cultivars for the cold hardiness evaluation has been planted, with a total of 118 accessions.  This planting contains the most complete comparison of olive cultivars in the Pacific Northwest. This site will be evaluated at the plants grow, and as cold winters occur, noting plant growth, olive fruit data, and cold damage. Olive growers will continue to have access to the information from this trial allowing them to compare cultivars in our region and decide what grows best in our climate.

Temperature and winter cold damage tracking was done annually at grower collaborator sites, with growers having immediate access to all of their farm’s weather data. Winter cold damage data collected each following spring has also been shared with growers each year.

 Transplanting and up-potting practices

Overall have found that in years with mild winters, and fields with only establishment/limited irrigation, more tree losses occur in spring and summer than in winter. However, in fields with irrigation, spring planting is preferable to fall planting. We have also found that young trees are particularly sensitive to over and underwatering, with root rot as a primary concern in both the field and greenhouse. Otherwise, pest/disease pressure has been very low. Without the ability to test the hypothesis of older, larger trees showing better establishment than smaller, younger trees, we are not able to say if up-potting and overwintering gives an advantage, as high amounts of vegetative growth were seen in trees transplanted at both sizes and ages. Across both sites, production systems, and multiple years, ‘Leccino’, ‘Frantoio’, and to a slight lesser extent ‘Amphissa’ show increased growth compared to ‘Ascolano’, suggesting that these cultivars may be adapted to growing in a climate such as Oregon’s.

Our main collaborator for the up-potting trial has been O. O. Agriculture/Compton Chase, a grower who is replicating our practice of keeping plants in a protective greenhouse over the winter for one or more seasons before planting. This was the third winter that this collaborator has been overwintering their plants, with some plants from the initial batch ready for planting in the field fall 2020. For the third year in a row, we have installed a temperature and RH sensor in their greenhouse, and have found it valuable to compare this data to that of our own overwintering greenhouse. There are plans to collect observational data in this grower’s fields in the following years to determine the success of their adoption of the up-potting methods.

  1. Outreach

While the first years of the project laid the groundwork for future communication and collaboration between the research team, growers on the Advisory Council, and the general public, the COVID-19 pandemic required swift adaptation, flexibility, and creativity in order to continue buildings these relationships and disseminating research findings. Growers have been able to share input both in formal meetings as well as through less formal farm visits and interviews. We plan to continue participation in industry and other outreach events. The website and Instagram account have also served to inform a wider audience about research progress.

Success stories:

A Yamhill County olive grower has credited our project with multiple improvements in propagation as well as monitoring of weather patterns for field establishment. Two additional olive growers who now propagate their own olives also credit the project with improvements in their techniques and rooting percentage increases. 

The Olea Project Instagram account was used to great success in the early days of the COVID-19 pandemic, in order to host virtual tours, workshops, and webinars focused on olive pruning and propagation. These Instagram-live events were extremely well attended, and drew a wider audience than may have been possible with in-person events.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.