- High tunnels are unheated structures that resemble greenhouses and allow crops to be grown earlier and later than outside by utilizing the natural heat gain inside the structure. They provide advantages like earlier and later production, higher yields, natural pest and disease control. - Crops that can be grown include vegetables normally grown in the region like tomatoes, peppers, cucumbers, which produce earlier and have higher yields inside high tunnels. - Key components of high tunnels include good drained soil, roll up sides, UV treated plastic covering, and can be built from various materials like wood or metal frames. High tunnels take advantage of the principles of plant growth related to time, heat and light to extend the growing season

1. Basics of High Tunnel
Production - 2012
Terrance T. Nennich
Extension Professor
Vegetable and Small Fruit Production
University of Minnesota Extension
nenni001@umn.edu

2. High Tunnel Research Sites in
Minnesota
Experiment Stations
Grower Cooperators

3. What are High Tunnels
• High tunnels are not a poor persons
greenhouse
• High tunnels are a separate intense
technology which allows crops to be
grown up to three zones earlier and later
and eliminate considerable risk.

5. What are High Tunnels?
• Structures that resemble some
greenhouses - in appearances only
• Use no artificial heat (except for
emergencies)
• Use no artificial ventilation such as fans,
tubes or forced air
• Plants are grown in the ground.
• Many shapes and sizes

7. What Can be Grown in High
Tunnels in Zones 2 and 3.
• Any crop that can normally be grown in
the area
• Most crops in zones 4 through 5.
• Some in zone 6 and be on.

21. Winter Tour

26. Advantages of High Tunnels
• 4-8 weeks earlier production in the spring
• 2-5 weeks later possible production in the
fall
• Grow crops not usually grown in the area
• Very high yield per plant
• Crop mix
• Very cost effective
• Usually no pesticides needed
• Organic production

27. Advantages of High Tunnels
• Natural disease control
• Insect control
• Control water
• Guarantee a crop
• Reduce cull fruit.

28. Advantages of High Tunnels
• Natural disease control
• Insect control
• Control water
• Guarantee a crop
• Reduce cull fruit.

29. Concerns of High Tunnels
• Cost involved
• Education
• Planning
• Management
• Time

30. Key Components of high Tunnels
• Good well drained raised soil
• Roll Up sides
• 6 mil UV treated plastic
• Can be built from many materials

51. Why High Tunnels Work
• Lets review the principles of plant growth
Time
Heat
Light
Stress

52. Time
• All plants need time to advance in growth and
mature
• How much growth that occurs in a given length
of time depends on how ideal the environmental
growth factors are.
• In northern climates heat is the one factor that
we need to be concerned about.
• Seed catalogs use maximum conditions in
deciding growing days.

53. Heat
• Plants are classified by there ideal heat
requirements.
• Tomatoes , peppers, 80-90 degrees
• Cucumber , melons , 85-95 degrees
• Heat is measured in growing degree days
• Duration of Temperature is Critical

54. Growing Degree Units
• Normal figure used for warm season crops
is 50 low and 86 high
• Growing degree Units =
(high for day+ low for the day) – 50
Divided by 2
(86) (50)

55. Growing Degree Days units for
Tomatoes
• Early to mid-season tomatoes will require
1400 to 1600 GDD to the first ripe fruit.
• Late season varieties will require 2000 to
2200 GDD

56. Growing degree day samples
Low of 40, high of 60 = 5 GDD
Low of 40, high of 50 = 0 GDD
Low of 50, high of 70 = 10 GDD
Low of 60, high of 86 = 23 GDD

57. Growing Degree Comparison
Inside and Outside Tunnel
• Inside Tunnel • Outside Tunnel
• March 281 GDU • March 5 GDU
• April 435 GDU • April 99 GDU
• May 502 GDU • May 183 GDU
• June 570 GDU • June 366 GDU
• July 624 GDU • July 505 GDU
• Aug 544 GDU • Aug 374 GDU
• Sept 570 GDU • Sept 396 GDU
• Oct 303 GDU • Oct 101 GDU

58. Growing Degree Days units for
Tomatoes
• Early to mid-season tomatoes will require
1400 to 1600 GDD to the first ripe fruit.
• Late season varieties will require 2000 to
2200 GDD

59. High Tunnel Planting Dates
Northern Minnesota
• Onions , radishes, lettuce Mar 25-Apr 7
• Cabbage, broccoli ect Apr 7-15
• Tomatoes, peppers April 25 -
May 10

60. Different Locations in the state
• March 31
• Bemidji Minnesota high 45 Low 20
• Austin Minnesota high 47 Low 28

61. • January 2006

72. Production Data
• Tomatoes : first harvest in tunnel July 18
• First harvest outside Aug.11
• Yield 10-25+ per plant
• Cucumbers: first harvest June 16
• Yield per plant 30-35 pounds

73. Common Mistakes Beginning
Growers Make
• Tunnels get to hot >130+
• Don’t shut roll up sides early enough in
the evening-loose growing degree units
5 GDU a day for a month = 5-8 day
• Weed Control inside and out
• Monitor the water uptake
• Punning and trellising

75. Tunnel Direction
• Narrow end against prevailing high winds
• The outside air direction has little to do
with the cooling of the tunnel
• Recommend tunnel construction for 100
MPH winds

107. Yield Potential & Nutrient Needs
• Yields in a high tunnel can be 3 to 4 times the
yield obtained in the field
• Higher yields will required more nutrients, but
knowing how much to apply is a challenge
– Lack of nutrients – deficiencies
– Excessive nutrients – salt build up
– Both situations affect yield and quality

108. Cucumber Results
Cucumbers
All the fruit from all 26 cucumber plants were weighed
and evaluated for quality. All data is in pounds per plant.
Sweet Success
First Harvest June 8
Total Yield/Plant 65.12
Culls 8.0
MKT/sq/ft 9,52
Total sq/ft 10.85
Total Yield Acre = 472,628 or 236 tons.

109. Soil Nutrient Research
Sweet Success Cucumbers
0-6 inch soil depth
N P K
Before Season 335 330 1050
After Harvest 12 175 256

110. Soil Nutrient Research
Sweet Success Cucumbers
6-12 inch soil depth
N P K
Before Season 100 150 580
After Harvest 7 69 320

111. Tomato Results
Variety First harvest Total yield Culls Marketable sq/ft Total
sq/ft
Cobra June 28 37.0 4.0 3.89 4.63
Sunshine June 24 16.5 5.1 1.90 2.75
Mt. Spring July 11 18.5 4.2 2.38 3.08

112. Soil Nutrient Research
Cobra Tomatoes
6-12 inch soil depth
N P
K
Before Season 100 150 580
After Harvest 8 80 320

113. Soil Nutrient Research
Cobra Tomatoes
12-24 inch soil depth
N P K
Before Season 18 60 275
After Harvest 8 55 260

114. Soil Nutrient Research
Cobra Tomatoes
0-6 inch soil depth
N P K
Before Season 335 330 1050
After Harvest 11 215 235

125. Berry quality

134. High Tunnel Roof Vent

142. • Air leaves the solar panels at about
125-175 degrees depending on the
amount of sun
• Air leaves the soil at 50 – 75 degrees to
be recirculated through the solar panels
(this is a closed system )

147. Solar Heating of the Soil
• Cucumbers – May 15
• Tomatoes – June 5

148. Results to Date
• Soil temperatures have been kept at
minimum of 52 degrees even though
outside temperature have been well below
10 degrees.
• At this temperature, cool season crops are
doing very well

149. Local High Tunnel List Serve
• Be sure to sign up for the Minnesota/North
Dakota List Serve.
• Talk to local producers, be informed of
upcoming events.

150. On line at:
www.hightunnels.cfans.umn.edu
Minnesota Fruit and Vegetable
Growers Association – (763) 434-0400

151. Minnesota High Tunnel Web
Site
•http://hightunnels.cfans.umn.edu/

153. Upcoming Research
• Plant density studies
• Fertility studies
• Variety Studies
• Irrigation Studies
• Raspberries, Perennial crops , Overwintering

154. Seminars on High Tunnels
• Getting Started with High Tunnels
• Crops and Yields
• Marketing
• Soil Fertility/Nutrient Use
• Irrigation
• High Tunnel design
• Organic Production
• Fruit Production

155. QUESTIONS
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