Scaling up on-farm drying equipment for Elderflower and other perennial herbs in the Upper Midwest.

Final report for FNC20-1242

Project Type: Farmer/Rancher
Funds awarded in 2020: $17,726.00
Projected End Date: 12/31/2022
Grant Recipient: Main Street Project Research and Demonstration Farm, LLC
Region: North Central
State: Minnesota
Project Coordinator:
Wyatt Parks
Main Street Project Research and Demonstration Farm, LLC
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Project Information

Description of operation:

Sharing Our Roots (formally Main Street Project) operates roughly 100 acres of diversified perennials, grazing systems and high value specialty crops. Crops include: Elderberry and Elderflower, dried Botanical herbs, garlic, asparagus, hazelnuts, fruit and hay. Before receiving this grant we implemented sustainable practices such as cover cropping, perennial ground cover, multi-species rotational grazing, and an overall perennial based farm design. The farm was established in 2017 and has been certified organic since 2020.


Farmers looking to produce small fruits, and particularly elderberry, have always struggled to manage pests. In both organic and conventional settings management practices have been limited to what is safe for the plants and what is safe for the end consumer. As many small fruits are consumed as field fresh products special care has to be given to factors like post-spray harvest windows and transport durability. All drosophila species present a risk to product quality but Spotted Wing Drosophila (SWD) poses a particular challenge. SWD’s ability to lay larvae in unripe fruit means that management needs to begin earlier in the season and extends all the way to the end consumer.

Spotted Wing Drosophila’s life cycle is highly dependent on access to fruit and berries in which to lay their larvae. Elderberry in particular appears to be a favorite host species for SWD in the Upper Midwest as there is a wide abundance of plants growing around farms, ditches, and windbreaks. In commercial settings this host-pest relationship is critical to manage if the farmer wants to yield quality produce. Our project aimed to test the hypothesis that by removing host fruit the number and impact of SWD can be significantly reduced over time.
Our plan to scale forced drying equipment offers a strategy to reduce SWD prevalence in elderberries by creating a marketable product from the flowers. The U.S. currently imports the majority of its elderberry and elderflower products from Europe though many Midwestern farmers are adding elderberry to their diversified operations. An appropriate scale of stand alone forced drying equipment suited for mid sized elderberry and elderflower producers does not currently exist and there has been little effort to develop this type of on-farm processing equipment in our region. Food and beverage companies, and retail health food stores, are interested in sourcing dried elderflower (and other herbs) locally instead of from large-scale herb distributors. Currently, local growers cannot supply these markets with an appropriate quantity of dried elderflower because of the inefficiency of small scale equipment.

Our research approach is two fold, observe the impacts of host-habitat reduction in our elderberry field and test the production and market viability of dried botanical products. We view that it is important for both of these two areas to be tested simultaneously as one without the other will fail to be a commercially viable business. In our elderberry patch we have been focusing our harvest capacity exclusively on the flowers since 2020. At the same time we have been working on improving our dryer system to constantly yield quality botanical products.

Our market and dryer development has so far been a significant success. Through our field day, one-on-one meetings, and word of mouth we have had the opportunity to share our experience and provide feedback to existing and would be farmers. The infrastructure at Sharing Our Roots has also created the opportunity for our land access program participants to develop their own dried botanical based ag businesses.

Our results in impacting the prevalence of SWD in our field has been harder to quantify. Both 2021 and 2022 saw significant drought impacts on our area. One consequence of this was the reduction of potential host plants in the areas surrounding our farm as well as the increased day time temperatures regularly exceeding the max breeding temperature of SWD. We believe our harvest system did reduce the SWD population present in our field but also believe environmental conditions played a significant role in our success. The plan is to continue a flower based harvest regime in the coming years that will continue to provide insight into the impacts of SWD. 

While we have provided a number of farmers as well at the Midwest Elderberry Coop with design instructions for our dryer and preliminary observation of our field harvest plan we do not know of any farmers that have explicitly adopted our system on their farm.

Project Objectives:
  • Scale up on-farm forced drying equipment for herbals, specifically elderflower to meet current yield and
  • Increase supply of shelf stable, value-added dried elderflower for local and regional food, beverage, and health
  • Share findings with other farmers through field days and conference
  • Long term: reduce on-farm Spotted Wing Drosophila presence in elderberry crop by harvesting pre-fruiting flower and reducing overwintering habitat for
  • Long term: test and expand forced drying equipment ability to include additional specialty crops.


Materials and methods:

We began the project by reviewing the existing methods available for drying of botanical crops. This included reviewing dryers as small as at home countertop type dryers to much larger commercial kitchen models. We also looked at commercial scale forced air, microwave, and tunnel dryers to understand how large industries approached drying of products. Generally speaking there is a lot of available information about the function and technique employed in small home scale dryers and less available for the larger models. Published marketing materials, manufacturer websites, and demonstration videos provided the majority of material reviewed. As we had already determined that using a shipping container was the best platform to begin with due to prior experience with a similar dryer, we used the review period to identify what traits of other units were most important to incorporate. 

Initially we planned to collect information regarding initial moisture content, weight, color, and aroma for the harvested and dried elderflower throughout the project. As harvest got underway we began to focus exclusively on harvest weight records and spent little time recording data on other characteristics. The logic of this was to focus first on the financial viability of the crops rather than the final quality. As such 2021 harvest records were quite detailed including the initial wet weight as well as the final dried weight. Financial viability was then estimated based on labor costs per row feet. Harvest records and yields are included for 2021 and a summary of dry dow ratios and drying duration was collected for 2022. 

Market development work was primarily completed in 2020 and 2021 and focused on small commercial scale buyers. Working with the buyers we were better able to understand the forms and quantities that are needed in the marketplace. 

Spotted Wing Drosophila (SWD) monitoring was performed every year from 2018 through 2022. Drosophila specific traps were used to help in the positive ID of SWD within the field. Observation data was collected and notes take regarding the first noticed presence of SWD as well as the relative density and impact on the existing fruit.

Research results and discussion:

Effects on Spotted Wing Drosophila 

As part of the grant project, Sharing Our Roots staff conducted both observational and trap based surveys of Spotted Wing Drosophila (SWD) in their elderberry field. Observations were collected weekly to coincide with existing harvest days throughout the normal harvest season in 2020, 2021, and 2022. Traps were used in 2021 only to allow for the positive ID of SWD as well as other drosophila species that were present. A summary of results is presented below followed by a brief analysis of trends.

2018: Suspected SWD first observed by staff in elderberry field. SWD was likely present prior to 2018 but no existing staff member was trained to ID the pest. Harvest had also previously been intermittent so effects on berry quality had not been significant to harvest yields. In 2018 there was a noticeable degradation of expected harvest quantity and quality when compared to published standards and yields by other growers. The berries were immediately frozen post harvest in accordance with Midwest Elderberry Coop standards but ultimately were unfit for sale. The primary concern was the flavor and sugar content appeared to have been heavily affected by SWD infestation.

2019: Due to the previous year's harvest failure the decision was made to not expend any staff time on harvesting berries for market. A small amount of the fruit was harvested as U-Pick by a handful of customers who were willing to sort the available fruit to maintain quality standards. As a result of this 2019 had the most significant infestation of SWD of any year from 2018 onwards. At any given time during the active fruiting season there was SWD present on each berry observed. SOR staff also constructed a small forced air dryer from plywood and a leaf blower as an initial test of drying elderflower. Weather conditions were highly favorable for SWD throughout the season. Ample rain and relative humidity fostered near perfect conditions for the lifecycle of SWD.

2020: In 2020 baseline monitoring of SWD was begun by SOR staff. The initial goal of monitoring was to positively identify SWD alongside other drosophila species. At a glance it can be difficult to distinguish between them and as the season progresses the prevalence of other drosophila species increases. The first field observation was conducted the same week as the first flower harvests; the last week of June. At that time no significant infestation was observed. At our site the majority of the harvestable flowers are available over a three to four week period. In that time roughly 60% of the harvestable flowers were removed completely from the field. The first observation of SWD came in mid-July and coincided with the beginning of fruit set in the elderberries. This observation indicates that early and timely harvest alone would not be sufficient in avoiding damage from SWD as the flies are appearing prior to any fruit becoming fully ripe. This is an issue unique to SWD as most other drosophila species would be unable to cause significant damage in unripe fruit. The presence of other host plants, including wild elderberries, in the immediate area of our farm allows for SWD to proliferate prior to the elderberry harvest. It did appear that as the season progressed the volume of SWD present began to decrease. Regular observations were not conducted after the commercial harvest period was over but field walks in late July and August saw fewer drosophila on the remaining crop. Environmental conditions and a reduction in host fruit are believed to have played a key role in a decrease in SWD present. A small flock of sheep was also allowed to graze the elderberry field after the harvest had been completed. The goal was to reduce low lying vegetation around the plants that various pests utilize.

2021: There was a significant reduction in SWD observed in the field in 2021. Traps showed an overall decrease in drosophila present, not just SWD throughout the season. Salt bath tests observed no drosophila larvae at the time of initial fruit set. A goal of harvesting 75% of the flowers was established at the beginning of the season and was nearly met. A handful of rows of elderberry were also removed prior to the start of the season. The goal of doing so was to increase airflow around individual plants and decrease the amount of vegetative habitat around the base of the plants. The low, moist, and stagnant area around the base of the plant is perfect habitat for SWD larvae and adult flies to reproduce. June 2021 also saw incredibly high temperatures. The two weeks leading up to the initial harvest had day time temperatures averaging over 90 degrees at the farm. SWD is highly sensitive to temperature for its breeding cycle. Roughly 70 degrees is the optimal breeding temperature and as temperatures increase above 90 degrees their ability to reproduce drops off significantly. The summer of 2021 also was at the beginning of a significant drought affecting both commercial crops as well as wild host species. This combination of environmental factors is likely the primary contributing factor to a reduction of SWD observed in the field. Starting a few weeks after the fruit set, evidence of SWD began to be visible. Most umbels had some evidence of fruit fly damage but not all berries appeared to be affected.

2022: A continued decrease in SWD presence was observed in the field. The entire crop appeared to be highly affected by the continued drought reducing the total number of flowers and the duration of plants setting new umbels. An interesting impact of the drought appeared to be an increase in early fruit termination. Many of the plants exhibited increased water stress that resulted in fruit being aborted prior to reaching full ripeness. Even the few berries that appeared to reach maturity had no sugar development and were smaller than previous years. The vast majority of the fruit in the field never made it to this stage though. As a result no SWD was observed in the field at any point in the season. As SWD specific traps were not utilized this year we do expect some flies were present, just not on the plants and berries observed. The total harvest of flowers appeared to be depressed throughout the season. Many plants will continually produce new flowers until August but very few did so in 2022. Anecdotally it appeared there was a 90% reduction in late season flowers compared to previous years. The impact of this on future years' SWD presence is not entirely known but we expect a continued suppression of SWD populations for the next few years as a result of this.

Dryer Description

The dryer is made up of a 20’ shipping container. We chose a used unit that was in near new condition with good working doors, intact air seals, and clean interior. To convert it to a dryer we added 6 one-way 4” air vents along the top of the walls of the container. These vents included bird screens to prevent pest intrusion. On the floor we installed a custom cut grain bin floor with 0.05” perforations. We also used the supplied floor support system though we would recommend having the floors cut to the width rather than the length of the dryer and simply using stand 2x6 framing lumber to support the floor. Or initial design utilized a transition to pull air from outside the container in through a hole that was added on the back wall of the container. The hole was cut such that the fan discharge was underneath the bin flooring. One of our major adjustments was to remove the transition, block the hole and move the fan inside the container. This eliminated the introduction of excessively moist air and significantly reduced the volume of the dryer from the outside. A dehumidifier was also added to reduce the interior humidity and help in the drying process. Various other shelves and bins were utilized to maximize the available space in the dryer.

Botanical Drying time and yield results.


In 2020 we did not collect significant harvest or drying time records. Our primarily goal was to run small batches of a variety of products through the dryer to observe what happened with each. We watched temperature and humidity most closely and used that insight to make changes for the 2021 season


Expected drying time and fresh-to-dry ratio varied significantly between different crops. The chart below shows the recorded fresh and dry yields for each of the crops monitored for the project in 2021. Both Red Clover and Feverfew were excluded from the average ratio as records were incomplete for both these crops. The dry yield figures also include shrinkage from the final sifting stage of the crop. This step was primarily to remove stems and foreign material from the crops where needed. Some crops needed no removal of stems as the entire plant was marketable thus increasing the ratio. 

Environmental factors like humidity at harvest, wind speed, temperature, and time of day all also contributed to yield ratios and drying time but are not effectively captured in the data. Harvest time and duration was primarily affected by staff availability and not optimum timing for maximum yield. Harvest technique also played a role in the ratio but that information was not recorded as part of this grant.

Each crop was harvested an average of 12 times throughout the season suggesting that a variety of environmental conditions were experienced during harvest. The only conditions that were never experienced was during or immediately after a rain event. Plants were checked to confirm no surface moisture was present prior to harvest.

Most crops on average had dried to storage safe moisture contents within 48hrs of entering the dryer. As the ambient temperature increased throughout the season the drying times fell to as little as 24 hrs for light and thin crops while climbing to three to five days as temperatures decreased in the fall. The key factor in preventing damage to the crops was humidity fluctuations in the dryer itself. Our initial dryer design that we used in 2020 was pulling air in from outside the container 24/7 but for 2021 we altered the dryer configuration to recirculate the air already in the dryer.

2021 Harvest Data





Anise Hyssop












California Poppy












Lemon Balm




Mountain Mint




















Red Clover













In 2022 Sharing Our Roots began the process of transitioning their botanical production to one of the farmers participating in their land access program. Delanie Harrman of So Below Apothecary, who previously had worked for Sharing Our Roots Farm, assumed production and drying responsibility for the existing botanicals on-site as well as introducing new crops as part of her business. Included is a summary of her 2022 season including information about dryer management, observations, and harvest dry down ratios.

General Overview

In 2022, I grew over 18 varieties of aromatic and medicinal botanicals to dry in Sharing Our Roots custom dryer.  Overall, the dryer worked well to dry the botanicals just as it did last year and I would recommend this set up to botanical farmers. However, I identified three major improvements that could be made to the dryer, which are maintaining consistent temperature, lowering humidity, and organization. Below I will also include proposed solutions for 2023 to increase drying efficiency and yield. 



The dryer was operated from June 3, 2022 through October 15, 2022, and outside temperatures ranged from 30°F - 94°F.  Inside the dryer would average 7 degrees higher than the outside temp, but this could be lower if there were consecutive cloudy days, and higher for intense sunny days.

The first, and biggest, issue faced this year was the temperature of the dryer.  Temperature fluctuations would speed up or slow down the drying process by several days, leading to an unreliable harvesting schedule.

The dryer worked best when outside temperatures reached at least 78°F, and higher temperatures resulted in faster drying, improving overall yield. In southern Minnesota, this gave me about 3 months of ideal drying time, but the season in which to harvest botanicals can last around 5 months.  

I found the majority of botanicals I grew this year dried best at  90°F - 95°F. At this temperature, the color and aroma stayed intact, and they dried quickly.  A small heater in the dryer would help maintain consistent temperatures throughout the season, and add season extension to include early season botanicals (eg. dandelion greens and flowers, stinging nettle) and frost hardy herbs (eg. calendula, mint).  This year we experienced an early frost, and everything that was in the dryer was lost due to inefficient temperatures outside, and this could have been easily prevented with a sufficient heater.


To control humidity within the dryer, a dehumidifier was run continuously, set at 30% humidity.  A hose was installed in the dehumidifier so it could run at all times, without the need to empty it.  Impacts on the humidity in the dryer included rain and general humid weather, but nothing incredibly significant.  The biggest impact was created by fresh plant material placed in the dryer, which would spike the humidity.  


This year the dryer was fit with two different types of shelving on which to dry botanicals.  One side was lined with bread racks, used to dry flowers and botanicals with low water content, such as calendula, elderflower, and echinacea leaf/flower.  The bread trays were 6” deep, so a single layer of flowers lined the bottom of each tray to promote air flow.

The other side of the dryer was fitted with three 48” NSF food safe epoxy wire shelving.  The individual shelves were spaced 15” apart to accommodate large botanicals.  Herbs with a high water or essential oil content, such as anise hyssop, tulsi, and sage, were evenly layered 3”-8” thick when fresh on the racks.  As the botanicals shrunk during dry down, they were spread out again to promote faster dry time.

Both shelving systems worked well when used as outlined above.   The bread racks were especially nice as they kept all the botanicals fairly confined. There was minimal loss in terms of plant material falling to the floor and becoming contaminated with other plant material.  

The epoxy shelves resulted in some loss of plant material, as the space between the wire allowed material to drop to the floor.  Though the floor under the racks is also a food safe space, this year I dried a different species of botanicals on each of the racks, and all three botanicals would fall to the floor, mix together, and contaminate one another.  

Next year I will do a big harvest of one botanical species to fill the epoxy racks with at a time, so that way I can also utilize the floor space under the racks and increase my yield. 


Botanical Drying Results


Rack Type

Days to Dry


Anise Hyssop

(Agastache foeniculum)

Epoxy Wire Shelf

3-4 days


Basil, Sweet

(Ocimum basilicum) 

Epoxy Wire Shelf

5-7 days


Basil, Cinnamon

(Ocimum basilicum var. cinnamomum) 

Epoxy Wire Shelf

4-6 days



(Calendula officinalis)

Bread Rack

5-7 days


California Poppy

(Eschscholzia californica)

Floor of Dryer



Chamomile, German

(Matricaria recutita)

Floor of Dryer

2-3 days


Echinacea Flower

(Echinacea purpurea)

Bread Rack

6 days



(Sambucus nigra)

Bread Rack

2 days



(Tanacetum parthenium))

Bread Rack

2-3 days


Lemon Balm

(Melissa officinalis)

Epoxy Wire Shelf

3-5 days


Mint, Bergamot

(Mentha citrata)

Epoxy Wire Shelf

3-5 days


Mint, Chocolate

(Mentha x piperita var. chocolate)

Epoxy Wire Shelf

3-5 days


Mint, Peppermint

(Mentha x piperita)

Epoxy Wire Shelf

3-5 days



(Mentha spicata)

Epoxy Wire Shelf

3-5 days


Monarda Flowers

(Monarda fistulosa)

Bread Rack

4 days


Mountain Mint, Slender

(Pycanthemum tenuifolium)

Epoxy Wire Shelf

2-4 days



(Salvia officinalis)

Epoxy Wire Shelf

4-6 days



(Ocimum tenuiflorum)

Epoxy Wire Shelf

6-9 days


Participation Summary
4 Farmers participating in research

Educational & Outreach Activities

2 Consultations
5 On-farm demonstrations
2 Tours
1 Workshop field days

Participation Summary:

25 Farmers participated
10 Ag professionals participated
Education/outreach description:

In 2021 we were able to host an in-person Elderflower workshop at our farm as well as continue some 1-1 conversations with individuals interested in our work. We also were able to include demonstrations of our dryer to participants of a Climate Land Leaders event and a Minneapolis Foundation staff and donor event hosted at our farm.

Learning Outcomes

5 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Lessons Learned:

The primary lesson learned regarding the dryer was the importance of conditioning the air entering the dryer. Uncontrolled, the ambient air outside the container fluctuated too greatly to create quality dried botanical products. Humidity had the greatest ability to affect the quality and could easily ruin a dryer full of product if not controlled. We briefly looked at various ways of controlling the characteristics of incoming air including altering the timing of the fan running, ie turning the fan off and on based on relative humidity. The problem with this method was we lacked staff capacity to have someone return to the farm late in the evening and early in the morning to turn on the fan as needed. Automation could account for this but the expense of building a system at the time felt prohibitive. 

Another valuable lesson we learned was in the management of space within the dryer. The examples we used to base our design off of all placed material directly on the floor and only dried a single product at a time. This approach allows for a more tailored drying method but is difficult for smaller producers to replicate. Our dryer regularly had multiple crops drying all at the same time requiring some level of separation to avoid cross contamination and intense monitoring to prevent damage to product from over or under drying. So Below Apothecary’s implementation of a rack and bin system was key to full utilization of the space. The density and volume of product able to be dried at any time was increased substantially by adding shelves that moved product off of the floor.

Project Outcomes

1 Farmers changed or adopted a practice
4 New working collaborations
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.