Growing Blackberries Organically under High Tunnels for Winter Protection and Increased Production

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1 36 Fruits and Vegetables Gundacker Principal Investigator Erik Gundacker Scenic Valley Farms Danbury Way Rosemount, MN com Dakota County Project Duration 2009 to 2011 Award Amount $19,445 Staff Contact Jean Ciborowski Author: Cassie Boadway Keywords blackberry, high tunnel, trellis, winter protection Growing Blackberries Organically under High Tunnels for Winter Protection and Increased Production Project Summary Can organic blackberries be grown commercially in southeast Minnesota? Scenic Valley Farms (SVF) has been growing blackberries on a limited scale, and with limited success, using the labor intensive practice of tipping the plants and covering them with mulch for winter protection. Growing blackberries in high tunnels with auxiliary heat should allow us the opportunity to commercially produce organic berries with a decrease in labor. We will evaluate the yields and survival of several blackberry varieties grown in high tunnels for winter protection. Project Description Scenic Valley Farms was started in 2008 in Rosemount, MN with the goal of growing blackberries for commercial production in a northern climate. Our company designs and manages high tunnels, semi and fully automated climate control systems, and subterranean solar thermal heating systems. SVF maintains five semi-automated high tunnels that produce blackberries, raspberries and tomatoes. Market research indicates an annual demand for one million pounds of organic blackberries in the Upper Midwest. We have received interest from several U.S. organic wholesale food distributors; including Organic Valley Coop, Naturite Farms, and Sun Belle Inc. We plan to produce 3 acres of blackberries under high tunnels and anticipate a yield of 30,000 lb/a/yr. While the regional demand for organic blackberries is large, growing commercial grade blackberries in Zone 4 or colder zones without winter protection is virtually impossible. For instance, commercial blackberry farms grow blackberry cultivars that are viable in Zones In Zone 5 and above, the practice of tipping blackberry plants and covering them with mulch for winter protection is commonly used. However, we have found that this practice in Zone 4 provides only minimal winter protection and results in the loss of more than 75% of blackberry plants. Poor winter survival and the resulting poor yield, combined with the high labor costs to cover and uncover the canes, makes growing blackberries in a Zone 4 or colder climate unprofitable. Drip irrigation and fertigation system.

2 Fruits and Vegetables Gundacker 37 High tunnel T/V trellis system. that grew this year were tied to one side of the strand and they will bear next year s fruit. The canes that produce fruit next year will be pruned to the ground to make room for the following year s primocanes. The ventilation system in the tunnel consists of end doors, motorized side curtains, circulation fans, and gable end motorized ventilators. All of these systems are controlled using sensors. In 2009, we planned to test seven thornless blackberry cultivars (Natchez, Ouachita, Apache, Doyle, Triple Crown, Chester, and Doyle) but they were not available when we went to purchase them. The blackberry varieties were selected for their early to late season maturation dates and by the recommendation of Dr. John Clark, a blackberry breeder from the University of Arkansas. We decided to order and plant the aforementioned varieties in May, Since, we already had Prime Jan and Prime Jim established we built a PVC high tunnel over them in an attempt to extend the season. The primary objective of the project is to determine the viability of growing organic blackberries under a high tunnel for commercial production in a Zone 4 climate. The second objective is to research, record and evaluate the crop production processes required to grow organic high tunnel blackberries for commercial production. The final objective is to design a portable forced-air cooling system to provide post harvest management of the berries. In 2009, we worked with Poly-Tex of Castle Rock, MN and consulted with Terry Nennich to design a high tunnel suitable for blackberry production. Our requirements included straight side walls with sufficient height clearance to support a 7 trellis system; a gothic peak for optimal snow load capacity; and a price that is competitive with other high tunnels on the market. Poly-Tex designed and developed the Field Pro using these specifications. We prepared the land for the high tunnel by using black plastic to smother weeds and then fertilized the soil using well rotted horse manure and recycled mushroom compost. The high tunnel was put up with help from our relatives and friends. Inside the tunnel we installed a wooden T/V trellis system to support the berry canes. The T shaped posts were spaced 10 apart with two strands of wire that run tip of T to tip of T for a total of four runs. The canes The soil in the high tunnel was amended by mixing in equal parts mushroom and dairy manure compost at a rate of one wheelbarrow full per ten row feet and was tilled in. After planting, the canes were mulched with a combination of mushroom compost and straw. The floricane blackberry canes were planted on May 15 in a 30 X 60 gothic style high tunnel, which included: Triple Crown, Arapaho, Chester, Apache, Ouachita, and Natchez varieties. The canes were planted in four linear rows 7 apart with the outer two rows 4.5 from the side walls. The plants were spaced 3 on center with 80 total in the tunnel. The floricanes were tied to the trellis wire and tipped at 6 to encourage horizontal growth. The small PVC high tunnel we built over Prime Jim and Prime Jan protected the plants over winter. As soon as the new canes reached 5 they were tipped and within 2 weeks laterals appeared that supported blossoms. We pruned during the season which encouraged new blossoms. Both high tunnels employ in-line drip irrigation Acclima SC6 controller.

3 38 Fruits and Vegetables Gundacker /10/10 6/24/10 7/8/10 7/22/10 8/5/10 and Acclima moisture sensors to regulate irrigation and fertigation cycles. The sensors measure moisture content as a percentage, soil temperature and soil conductivity. The Acclima controller monitors six zones and waters each as needed. Initially, the plants were provided 3 gal of water per day in two 1.5 hour cycles once in the morning and once in the evening. Once the primocane varieties began fruiting, the irrigation levels were increased to a total of 4.5 gal divided between three watering cycles. For fertilization we used a one gallon EZ flow fertigation system with an organic fertilizer containing bat guano. 8/19/10 9/2/10 9/16/10 9/30/10 10/14/10 Yield (kg) 10/28/10 11/11/10 of the berries experienced Botrytis fruit rot due to cool and moist conditions. We started closing the tunnel at night to raise the temperature and the fungus mostly cleared up as the result of the warmer temperatures. The final harvest occurred on November 18. After that date, auxiliary propane heat was suspended and the brambles were allowed to enter the dormant phase. The photos below demonstrate the season extension capabilities of high tunnels when coupled with propane heat. In the high tunnel containing Triple Crown, Arapaho, Chester, Apache, Ouachita, and Natchez floricanes contained a few brambles that bore small yields (several berries or less per plant). Typically, floricane blackberries do not produce until the second year and no approximate cause was detected for these plants early yields. The floricanes displayed no visible signs of disease or pests throughout the growing season. This is typical during the first year when foliage development is relatively minimal. The second and third years have a much higher incidence of disease and pest outbreaks so the brambles will be monitored closely. However, in the early winter months rabbits entered the high Project Results In order to control weeds we utilized three techniques. In the PVC high tunnel a layer of wood chips was spread on the floor. In the gothic style tunnel, we laid down sheets of cardboard before spreading wood chips. In a third high tunnel at our farm in Wisconsin, we rolled out mil black polyester material in widths of 3 and 6. The most effective technique appears to be the black polyester material, which also has the added benefits of controlling soil erosion and reducing labor. Prime Jim and Prime Jan began fruiting in early August. Harvest started in August and continued through November (Figure 1). Individual fruit size averaged between 6-15 g and was often difficult to pick at optimal ripeness because of its softness. These varieties have thorns that made picking more difficult and required that pickers wear gloves and flannel shirts. During the summer it was difficult to maintain optimal temperatures of F inside the high tunnel. Some poor drupelet formation occurred due to temperatures in excess of 100 F. We think high temperatures would be easier to remedy in the larger high tunnel because they have greater ventilation capabilities. High temperatures were not the only problem we had in our high tunnel. In early September a small amount Primocanes Prime Jim and Prime Jan.

4 Fruits and Vegetables Gundacker 39 Photo taken on November 14 in Prime Jim and Prime Jan High Tunnel. tunnel and girdled the canes. Roughly 10-15% of all the canes were either destroyed or badly chewed. Within 2 weeks, the rabbit would have destroyed all of the canes. Interestingly, the rabbit only attacked the young thornless floricanes. We blocked off the possible entrances and set two traps inside. A few days later, a rabbit was found in one of the traps and we have not experienced any girdling since. The plants took a long time to freeze in the late fall due to the warmth provided by the high tunnel. In addition, snowfall in December created an insulating effect and the tunnel was F warmer than outside temperatures. After they were dormant we used a thermostatically controlled 170,000 BTU propane heater that was set to maintain minimum temperatures of a zone 7b climate (5-9 F). The plants were watered heavily before the irrigation system was turned off. A lack of moisture throughout the winter is a concern and we will provide updates on how this affected the plants. We are also concerned an expected temperature increase in the high tunnel in February may promote premature budding. Overall, the project has reduced labor and input costs. The moisture sensors provide automatic irrigation and fertigation in the high tunnel. For instance, the drip emitters reduced the amount of water required and the in-line fertigation provided precise amounts of liquid fertilizers. The black polyester material and wood chips dramatically decreased the amount of time devoted to weed management. The major inputs of labor occurred during site preparation and harvest (although even these periods were very manageable). In addition, the same management techniques that reduce input costs also had a positive environmental impact by conserving water and reducing soil erosion. Market Potential for Blackberries We did not market any of our blackberries this growing season. Next year, we intend to develop markets for the floricane varieties under production at our farms in Rosemount and Readstown. Wholesale food dealers generally pay $5-6/lb for organic blackberries from June 1 through November 30. We have received strong interest from Sun Belle Inc. of Chicago and Bergin Fruit and Nut Company of St. Paul. Other outlets include supermarkets, grocer cooperatives, CSAs, restaurants, and farmers markets. The lack of locally grown blackberries creates a tremendous opportunity for any grower capable of bringing blackberry production closer to major cold weather markets. The local, organic aspect of the blackberries, along with their exceptional taste and freshness, should be emphasized in any marketing campaign. Management Tips 1. Laying black polyester material between the rows is the most effective weed management technique. We recommend leaving sufficient space between the material and the base of the plant in order to allow new canes to form. 2. Be careful to monitor and manage temperatures within the high tunnel. Attempt to keep the temperatures between F because higher temperatures increase the risk of improper drupelet formation, Botrytis blossom, and fruit rot. 3. Do not use fish emulsion based liquid fertilizer in a drip irrigation system with emitters because it will clog them. 4. When ordering brambles such as blackberries, order plants early, no later than February.

5 40 Fruits and Vegetables Gundacker 5. Continually pruning of Prime Jim and Prime Jan resulted in continual blossoming. 6. Partial shade negatively affects plant development. Cooperators Terry Nennich, University of Minnesota Extension, Crookston, MN Brad Becker, Dakota County SWCD, Farmington, MN Craig Gundacker, Scenic Valley Farms, Rosemount, MN Rebecca Harbut, University of Wisconsin, Madison, WI Kathy Demchak, Penn State University, University Park, PA Project Location From I-35E, exit at Pilot Knob Rd. (exit 97A) and go south about 5 miles to McAndrews Rd. Go east.7 miles to Danbury Way. Turn south. Scenic Valley Farms is.6 miles on the west side of the road. Other Resources High Tunnels website sponsored by Kansas State Research and Extension, University of Missouri Extension, and University of Nebraska Cooperative Extension. Nennich, T., David Wildung, and Pat Johnson Minnesota High Tunnel Production Manual for Commercial Growers. M1218.html Safley, C. D., O. Boldera, and G. E. Fernandez Estimated Costs of Producing, Harvesting, and Marketing Blackberries in the Southeastern United States. HortTechnology 16: extension/blackberry_budget.pdf University of Minnesota High Tunnel Production Website: hightunnels.cfans.umn.edu Raspberry and Blackberry High Tunnel Production Guide: hightunnelsrasp2009.pdf Pruning and Trellising Brambles: MDBayAreaBramble%20Pruningv2% Demchak.pdf Growing Raspberries and Blackberries in a High Tunnel Iowa State University: