- Fruits: berries (brambles)
- Crop Production: high tunnels or hoop houses, season extension types and construction
- Pest Management: cultural control
We propose to examine the feasibility of producing early season, floricane producing raspberries and blackberries in Colorado. Early season (late June or July) locally produced fruit is in high demand in Colorado. Fruit at this time of year sells at a premium price compared to late season fruit and has the potential to drive sales of other early season produce at farm stands and farmers markets. Further, early season fruit ripens before spotted wing Drosophila (SWD), a new and now key berry pest, is most active in the field. Development of economically viable early season berry production techniques would both increase farm revenues and reduce management costs and losses from this pest. For producers that follow organic management practices (such as ourselves) there are few management options other than rigorous culling of damaged fruit that are effective in managing SWD damage. Shifting the majority of berry production to earlier in the season has the potential to be an environmentally and economically sustainable production strategy. Early season raspberries and blackberries are produced on floricanes. These are canes that have grown for one season and that produce lateral buds in the fall that will then flower and fruit the following spring. In cold climates successful overwintering of floricanes is difficult. Plants must receive enough chilling under short day lengths so that buds are fully cold hardy before a killing freeze occurs. In spring, late freezes can kill the developing fruiting branches if plants break dormancy too early. Floricanes don’t reliably overwinter in Colorado, therefore fall bearing primocane fruiting varieties are recommended and are currently grown in the region. Primocane fruit is produced on canes late in the same season that the cane emerged from the plant’s roots. However late season (primocane) brambles have drawbacks. They are more susceptible to pest damage, early fall frosts reduce yields, and overall they command a lower price due to competition with the region’s tree fruit. High tunnels have been used in New York and other cold weather locations to extend the season for bramble production. By increasing air temperatures, tunnels provide some protection from late fall and early spring frosts and accelerate plant growth. However, Colorado experiences a greater frequency and severity of early- and late-frosts and freezing events. We do not know whether passive management of high tunnels will offer enough protection to the canes by themselves. In fact, high tunnels could accelerate plant growth in spring too much, increasing the risk of cane damage from late spring freezes. In this project we will actively manage temperatures in the tunnels so that plants receive enough chilling hours under fall, short day conditions to achieve dormancy before killing freezes occur, and so that plant growth is not accelerated too much in spring that frosts or freezes will damage the plants. We will do this through opening the sides and ends of the tunnels (reducing temperatures to maintain dormancy and/or slow plant development) and by using row covers, fans, and supplemental heat from portable heaters (if needed) to prevent killing frosts within the tunnels. We suspect that in cases of moderate frosts or light freezes floating row cover will retain enough heat stored within the soil to prevent damage to the plants. Air circulation within the closed tunnel might be useful in this regard as well. For more serious cold spells, a low power electric or propane heat would provide enough heat to keep temperatures from dropping below freezing. Note that the goal is to prevent frost damage – not to heat the tunnel to provide off-season produce. This project will determine if active management of tunnel temperatures allows for early season raspberry and blackberry production in Colorado. With the added protection of high tunnels and minimal supplemental heat, organic floricane raspberry production in this region may be very feasible. This project will compare results from of high tunnel raspberry production to field production with row covers. Further, the data we record on the efficacy of frost and freeze protection within tunnels would be useful for many other crops grown in Colorado and other cold weather locations. We will also transfer the results of this project to other small growers and the public. We will use a combination of facebook posts (Garden Sweet has more than 1,600 followers currently), YouTube videos ,and traditional extension fact sheets. Demonstration of project techniques and outcomes will also be delivered through two field days and presented at CSU’s annual Horticulture Farm field day.
Project objectives from proposal:
1) Measure internal and external temperatures and determine the efficacy of fall and spring temperature management within high tunnels using a combination of: a. Side and end wall ventilation for cooling, b. Fans for frost protection, c. Floating row cover for frost protection, d. Portable heaters for freeze protection.
2) Measure the effect of fall and spring temperature management on fruiting timing and yield for seven raspberry and blackberry varieties.
3) Measure insect and disease pest pressure on these varieties and compare these to those seen on raspberries grown in the open.
4) Transfer the results of this project to small growers and the public using extension publications, YouTube or other social media videos, facebook posts, and field days.
1) Construct high tunnel – Summer 2015
2) Establish seven varieties of brambles within tunnels – Summer 2015
3) Monitor and manage temperatures year round beginning – September 2015 through July 2017
4) Harvest and track yields of each variety inside and outside of tunnels – 2016 & 2017
5) Track insect pest pressure throughout project September 2015 – July 2017
6) Host field days in July 2016 and July 2017
7) Record progress for posting to facebook and YouTube (digital images and video) May – July 2016 and 2017
8) Record and analyze 2016 data in November 2016
9) Record and analyze 2017 data in November 2017
10) Create outreach materials summarizing project results and recommendations for high tunnel bramble production in Colorado in November 2017.