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

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2009: $5,100.00
Projected End Date: 12/31/2011
Region: North Central
State: Minnesota
Project Coordinator:
Erik Gundacker
Scenic Valley Farm

Annual Reports


  • Fruits: berries (brambles)


  • Crop Production: conservation tillage
  • Education and Training: demonstration, farmer to farmer, on-farm/ranch research, workshop
  • Energy: energy conservation/efficiency
  • Farm Business Management: budgets/cost and returns, marketing management, e-commerce, feasibility study, risk management
  • Pest Management: biological control, economic threshold, field monitoring/scouting, integrated pest management, cultivation
  • Production Systems: agroecosystems, organic agriculture
  • Soil Management: soil analysis, organic matter
  • Sustainable Communities: local and regional food systems, new business opportunities, employment opportunities

    Proposal summary:

    Growing commercial grade blackberries in zone 4 or colder without winter protection is virtually impossible. Commercial blackberry farms grow blackberry cultivars that are viable in zones 5 -10. In Zone 5 and higher the practice of tipping blackberry plants and covering them with mulch for winter protection is commonly used. However, we have found tipping blackberry canes in a zone 4 region and covering them with mulch provides minimal winter protection and results in more than 75 percent blackberry plant loss (results from 2007). Not only is blackberry production drastically reduced but the added labor to cover and uncover the canes with mulch, makes growing blackberries in a zone 4 climate or colder unprofitable. Currently high tunnels are primarily used in zone 4 for season extension (three seasons). High tunnels for winter crop protection have not been used due to:
    1) Insufficient testing of crop production processes used in a high tunnel.
    2) The high costs of erecting the high tunnel and its associated production processes.
    3) The difficulty in managing and automating the crop production processes.

    Objective One: Determine the viability of growing organic blackberries under a high tunnel for commercial production in a zone 4 climate and the amount high tunnels will increase yield compared to traditionally grown organic blackberries. This proof of concept project will determine if the capital investment and labor involved in growing organic blackberries for commercial production under a high tunnel is economically justifiable.

    Objective Two: Research, record and evaluate the crop production processes required to grow organic blackberries for commercial production. Specifically, the amount of irrigation and feeding required as well as the most efficient schedule; the heating/cooling processes needed to increase the temperature to a zone 7 climate; the ventilation needed to disperse the excessive heat and humidity generated by the enclosed high tunnel; and the security required to protect the crops from deer, turkey and other wild life.

    Objective Three: Test the following sustainable agricultural practices: (1) organic farming (2) Integrated Pest Management (IPM) that employs black plastic as an alternative weed control and weed elimination; drip irrigation, anti-condensation and rainfall protection to reduce pests; high tunnel cover and beneficial insects to control insects; and motion sensors and electric fences to prevent wildlife intrusions to insure wildlife preservation (3) bumblebees for pollination (4) nutritional management

    Testing- We will develop and test organic blackberries in a single high tunnel with the intent to duplicate the system for a commercial operation.

    • The land to be used has 5-6 foot perennial weeds including thistle and burdock. After removing weeds, the field will be covered with 6 mm black plastic and 4-6 inches of mulch. Smothering black plastic demonstrates weed elimination and control. Weed elimination occurs within two months, thereby allowing immediate planting versus waiting three years under traditional plowing. Employing black plastic to smother and control weeds is an acceptable organic practice as long as the plastic is removed after weed elimination.

    • 120 plants of 6 different thornless blackberry varieties will be planted in 6 foot and 8 foot rows.

    • A 30 footx96 foot snow-load-tolerant gothic-style high tunnel will be covered with an anticondensation plastic film covering (eliminating moisture drips on the foliage control disease.) The covering will radiate heat back into the ground at night trapping passive solar radiation. The plastic contains a high light diffusion percentage providing for fuller, more uniform plants. The berries will be planted in six-foot rows, versus the standard eight-foot rows, to take advantage of the light diffusion. Our goal is to increase yields by making the plants denser.

    • Cooling and circulation requirements will be semi-automatically managed. The high tunnel will be outfitted with a thermostatically controlled fan and curtains (roll up sides) to displace excess heat. Snow buildup on sides of high tunnel in winter prevent roll up sides for ventilation. The fan is needed in the winter to disperse excess passive radiation heat.

    • The high tunnel will be outfitted with a thermostatically controlled propane tube heater. The inside temperature needs to be controlled to induce zone 7 like conditions of 0 to 10 degrees. The floricane (next year's fruit canes) may be severely impacted if the temperature falls below zero degrees. On average, there are 27 below zero days in Southern Wisconsin and Minnesota and, therefore, auxiliary heat is needed to raise the temperature above zero degrees on those days.

    • The irrigation system will be semi-automatically managed by moisture sensors in the ground. Micro drip irrigation emitters will be placed next to each plant and a controller, using the sensor data, will be used to control the irrigation cycles. The only water the plant receives is from drip irrigation. Not allowing rain water to reach the plants helps control disease formation on the leaves.

    • The high tunnel fertigation requirements will be semi automatically nutrition managed. Total Dissolved Solids (TDS)IEC sensors/meters will be placed in the ground to monitor nutrient levels. Also soil analysis and leaf nutrition analysis will occur. Valves connecting the fertigation to the irrigation system will be manually turned on when it's time to fertilize.

    • Inside the tunnel will be placed 7 foot high trailing posts with t- wires. One side of the "t" for the primocanes and the other side for the floricanes. The plants will be aligned such that each row of floricanes are facing each other for optimum pollination and picking.

    • For optimum pollination a bumblebee beehive shall be located inside the high tunnel.

    • We will scout and monitor for spotted spider mites and whiteflies. If spider mites appear we will release predators such as a Neoseiulus mix. Other predators will be released if white flies or aphids appear.

    • The high tunnel security requirements (control of wild animals including deer and turkey) will be managed by motion/light sensors that control an electric fence attached to the tunnel.

    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.