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Gardening Beyond the Frost

Britney Hunter Horticulture Extension Faculty

Davis County

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250,000 Tiny Greenhouses, Each Containing One Head of Lettuce

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Overview

• Intro to high tunnel greenhouses

• Understanding weather

• Temperature management

• Growing calendar

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High Tunnels

Walk in, drive in

Don’t overheat as quickly as low tunnels

Space for mature plants

7’

14’ 2’

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42’ x 14’ USU High Tunnel

72 plants per tunnel

~10lb per plant

= 720 lbs!

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Backyard Warm Season Tunnel

Winter Squash

Beans Peppers

Tomatoes

Zucchini

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“Don’t try to create an endless summer; instead, work with the

seasons.” Farm manger, Barbara Fuller. La Nay Ferme in Provo

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Understanding the Weather

“Wind and frost (the true garden killers)…”

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Freeze Free Period (a.k.a Growing Season)

Utah Climate Center

http://climate.usurf.usu.edu/reports/freezeDates.php

Location Freeze Free Period (AVERAGE)

Logan (Cache) May 14 – Sept 26 (125 days)

Brigham City (Box Elder) May 4 – Oct 11 (159 days)

Kaysville (Davis) May 1 – Oct 13 (165 days)

Salt Lake Airport April 26 – Oct 18 (175 days)

Provo (Utah) May 1 – Oct 12 (165 days)

Moab (Grand) April 17 – Oct 17 (184 days)

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec

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Frost vs. Freeze

Definition of frost/freeze warnings issued by National Weather Service.

Warning Wind Speed Air temperature

Frost Below 10 MPH Above 32oF

Frost/freeze Below 10 MPH Below 32oF

Freeze Above 10 MPH Below 32oF

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Night Time Radiation Freeze 32°F

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GROWTH RESPONSE TO TEMPERATURE

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Temperature Responses Cool Season Crops

Crop Min Opt Max

Onion 45 55-75 85

Cabbage 40 60-65 75

Salad 45 60-65 75

Potato 45 60-65 75

Perennial 45 60-65 80

Warm Season Crops

Crop Min Opt Max

Bean 50 60-70 80

Corn 55 65-75 90

Melon 55-60 70-80 90

Tomato 65 70-80 85

Sw Potato 65 70-85 95

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How does it work? The original “greenhouse effect”

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Managing temperatures

High tunnel Low tunnel

Floating

row

cover

Ventilation and shade

• How cold or heat can plants tolerate?

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Cultural and Environmental

• Microclimates

• Plastic mulch

• Raised beds

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Covers Type Protection

*near freezing Advantages Disadvantages Cost/10

tomato plants

Row cover cloth (Reemay®)

2-4 °F Can leave on Can blow around, not air tight

$15

Plastic 2-4 °F Air tight Needs support Must ventilate

$18

Plastic + cloth 4-13 °F Better protection custom size

Needs support Must ventilate

$33

Wall o’ water 10-22 °F Can leave on Size, not air tight $33

Plastic/glass cloche 2-5 °F Air tight Size, must ventilate $80

Paper cloche (HotKap)

2-4 °F Inexpensive flimsy, limits light $10

*Environmental factors prevent 100% accuracy

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Air Temperature with Soil Heating Cables

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Cold Frames

• Temperature Protection

• depends on materials (2-10°F near freezing)

• Advantages

• Sturdy

• Compatible with automatic opener

• Greens year round

• Disadvantages

• Not big enough for mature plants

• Overheat quickly

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Tunnels

• Temperature Lift

• 2-4 °F near freezing • Added protection by stopping wind

(hard to measure)

• Advantages

• Tall enough to grow most plants

• Can be built for individual needs

• Disadvantages

• Must be ventilated • Can get expensive

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Tunnel Design: Low Tunnels

• Heat up quickly

• Not tall/wide enough for mature plants

Insect net

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Colorado State Extension

http://www.ext.colostate.edu/mg/gardennotes/722.html

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The Yearly Growing Calendar

- Mellow Management: Season Extension

- Small scale growers

- Backyard gardeners

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec

Cool Crops Cool Crops Warm Crops

Seed indoors warm Crops

Direct seed Thanksgiving cold crops

Transplant Thanksgiving cold crops

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Time Line – Garden High Tunnel

Seed tomatoes Mar. 1

Plant tomatoes April 15

Seed lettuce Jan 15 - Feb 15

Plant lettuce Feb 15 - Mar 15

COOL SEASON WARM SEASON

Seed spinach Aug 1 - Sept 1

Plant spinach Sept 1 - Oct 1

COOL SEASON

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Idea for winter watering:

• Use a large water tank for watering in the cold season – If by chance it does freeze solid, it will likely be during a

time when you don’t need water

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First Harvest July 7, 2009

Outdoors: ~ August 10

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Warm Season Tunnel

Winter Squash

Beans Peppers

Tomatoes

Zucchini

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Late July in Warm Season Tunnel

• “Lots of powdery mildew on the winter squash and zucchini”

• “Tomatoes and peppers are doing well”

• “beans have yet to blossom”

• “no fruits on the melon”

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Considerations for Success

• Drip irrigation

• Plant spacing

• Temperature requirements

• Fertilizer

• Pollination

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Summary:

• Covers and structures increases temperatures during the day so plants start growing earlier, and will fruit sooner.

• Ventilation and cooling is critical

• Covers and structures protect plants a little at night, but plants can still freeze

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Selecting a Design

Type Ideal Situation Why to use Why not to use

Cloth Cover Few plants Easy Benefit is limited

Cold frame Fanatic about greens Easy Not big enough for tomatoes

Low tunnel Don’t mind ventilating Custom size If you forget, the party is over

High tunnel Farming/ small business $ Premium Ventilation and maintenance

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extension.usu.edu/publications

Illustrated web version

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Keys to Success Soil amendment and aeration Between crops

Seeding tool makes it easy and fun

Wire support increases efficacy and keeps the cloth clean

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5 - 6’

SNOW LOAD

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Cost/Economics

• 14’ x 42’

• $500 (materials)

• ‘FarmTek’

• 14’ x 24’

• $800 to $1000 (materials)

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USU Garden Tunnel

$260.00

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Other Resources

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Questions?

http://extension.usu.edu