The document summarizes research on overwintering garlic in high tunnels. Over four years, garlic was planted inside two types of high tunnels and outside in fall. Garlic inside tunnels had a 92-95% survival rate compared to 2-79% outside. Tunnel garlic was harvested 3-4 weeks earlier and was 30% larger. In a subsequent study, 15 varieties planted in a tunnel all had over 85% survival, even with temperatures reaching -50F. The research demonstrates high tunnels can successfully overwinter garlic in colder zones 2 and 3.

1. Overwintering Garlic in High
Tunnels
Terrance T. Nennich
Extension Professor
Commercial Fruit and Vegetable Production
University of Minnesota Extension.
nenni001@umn.edu
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3. Purpose of the Research
The Question??
• With winter temperatures reaching as low as –
40 to – 50 F degrees in Zone 2 and 3 and the
inside soil of high tunnels receiving no snow
protection, would fall planted garlic inside
high tunnels survive the winter and produce a
good early crop of garlic the next spring?
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4. Research Strategy
• The variety Music Garlic would be planted
both inside high tunnels and in outside plots.
• If that was successful we would they try less
winter hardy varieties.
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5. Research Location
The location of the research was Bagley
Minnesota, about 25 miles west of Bemidji.
Zone 2 – 3
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6. • The garlic research project was conducted
over a four year period
– 2005, 2006 ( planted, harvested)
– 2006, 2007
– 2007, 2008
– 2008 , 2009
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7. Variety Selection.
• The variety Music was selected for the first
three years of this study.
• For the fourth year a large selection of less
winter hardy varieties were selected
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8. Tunnel Design
• Two different high tunnel designs were used in
this research project.
– Gothic V roof design
– Small round design.
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10. Planting Dates - Outside
The garlic was planted on the following dates
outside of the tunnel
The First Three years
2005 September 21
2006 September 23
2007 September 19
Six inches of straw was applied following
planting.
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11. Planting Dates Inside the Tunnels
2005 October 20
2006 October 18
2007 October 22
Six inches of straw was applied 30 day
after planting
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12. Cold Temperature Data
Days below 0 F Coldest Day
2005-06 17 days -37 F
2006-07 24 days -41 F
2007-08 33 days -38 F
The 2006-2007 winter had 8 consecutive
night -20F or colder.
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13. Snow Fall Data
• 2005-2006 Ample but below average
• 2006- 2007 Little snow cover
• 2007- 2008 Average snow cover
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14. Survival Rate (%) Inside Tunnel
Gothic
• 2005 – 06 94%
• 2006-2007 92%
• 2007-2008 95%
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15. Survival Rate (%) Inside Tunnel
Round
• 2005 – 2006 92%
• 2006 – 2007 87%
• 2007 – 2008 94%
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16. Survival Rate Outside Tunnel
• 2005 – 06 69%
• 2006 – 07 2%
• 2007 – 08 79%
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17. Harvest Data
• Average 3 year harvest was 21 -30 days
earlier in high tunnels.
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18. Size Difference
• The size of the garlic grown in the high tunnels
was about 30% more then outside.
– Hard to statically compare because of different
soils, fertility, rainfall, ect.
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19. Results
• The effect of extreme cold winter temperatures of
the variety Music Garlic grown in high tunnels in
zone 2 or 3 has little effect on garlic winter survival.
• The garlic grown in high tunnels had a much higher
survival rate and increased size then the garlic grown
outside. Drastic differences were noted in 2006 -07
when there was very little snow cover outside.
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20. 2008-2009 Research
• In the fall of 2008, 15 different varieties, many
soft neck were planted in the high tunnel for
a winter survival study
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21. Research Strategy
• 20 cloves from 15 different varieties were
planted in a Gothic high tunnel on October 20,
2008 to be harvested spring 2009
• Cloves were covered with straw at a 6 inch
depth.
• Drip tape was placed in the high tunnel before
planting
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22. Significant Weather Data
• In 2009 there were two nights that that
temperatures dropped near or below
-50 F
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23. Garlic Varieties Used
• Music
• Russian Silverskin
• Asian Tempest
• Moroccan Silverskin
• Blossem
• Moroccan Hardneck
• Chesnok Red
• Japanese
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24. Garlic Varieties
• Creole Red
• Inchellium Red
• Silver White
• Burgandy
• Montana Giant
• Spanish Red
• Chinese
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25. Results
• All varieties had over a 85% survival rate.
• The following slides picture the varieties
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39. Future Research
• Given this data, how will other perennial
plants overwinter in high tunnels????
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40. Questions
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