garden under cover: winter vegetable production in low tunnels

Garden Under Cover: Winter Vegetable

Production in Low Tunnels

Cathy Rehmeyer, PhD Four Petal Farm

www.gardenundercover.com www.motherofahubbard.com

Four Petal Farm Because Locally-Grown Should Always Be ‘In-Season’

Banner, Kentucky

Our Climate: Plant Hardiness Zone 6b

Winter Lows: 2014 = -8 F 2015 = -14 F Average snow (season total) = 24 inches

Eliot Coleman

Winter growing methods: Open field and low tunnels covered with

fabric row cover (no clear plastic!)

Urban Ag. Holler Ag.

Farmer’s Market

W i n t e r

C S A

Online Storefront

Restaurant Sales

Micro Greens and Edible Flowers

Farm to School

Value-Added Products

Summer is our “down-time.”

Find a niche and make it work for you!

Winter Growing:The Essential Elements

1. CHOOSING THE RIGHT PLANTS

The garden still freezes — the key is selecting the right crops that can take it.

January 8, 2014

January 9, 2014

January 14, 2014 (-8 F the previous week)

January 24, 2014

Five Cold-Tolerant Crop Families• Alliaceae (Leek, onion, garlic, shallots)

• Amaranthaceae (Beet, orach, spinach, swiss chard)

• Apiaceae (Carrot, celeriac, cilantro, fennel, parsley, parsnip)

• Asteraceae (Catalogna, chicory, endive, escarole, lettuce, radicchio, salsify, scorzonera)

• Brassicaceae (Arugula, Asian greens, broccoli, Brussels sprouts, cabbage, cauliflower, mustards, radish, rutabaga, kale, turnips)

Crops Appropriate for Low Tunnel Production: Root Crops• Root Crops (carrots, rutabaga, daikon radishes, beets,

turnips, parsnips, scorzonera, salsify, parsley root)

Crops Appropriate for Low Tunnel Production: Greens

Crops Appropriate for Low Tunnel Production: Overwintered Brassicas

Heirloom varieties are generally more cold hardy

Superior cold-hardiness

• selection by gardeners for centuries/decades prior to cheap transportation and the grocery store

Winter Vegetables (in decreasing order of cold hardiness)

Varieties (open-pollinated italicized)

Mache Vit, Verte de Cambrai

Scallions Evergreen Hardy White

Parsnips Harris Model, Hollow Crown

Asian greens* Chinese Thick-Stem Mustard, Serifon

Cabbage, overwintering Deadon, Marabel, January King

Spinach, savoy types Tyee, Bloomsdale Longstanding

Kale, Scotch types Dwarf Blue Curled, Winterbor

Leeks, winter varieties American Flag, Blue Solaise, King Sieg

Fava beans, small-seeded Diana, Sweet Lorane

Broccoli, sprouting Matador, Santee, Early Purple Sprouting

Garlic Inchelium Red, Georgia Fire

Collards* Blue Max, Champion

Rutabagas Laurentian, Purple Top, Gilfeather

Kale, Napus types Ragged Jack, Russian Frills

Cauliflower, overwintering Galleon, Mumbles

Asian greens* Senposai, Komatsuna

Carrots Napoli, Snow White, Danvers 126

Turnips, roasting Golden Globe, Purple Top

Kohlrabi Early White Vienna, Winner

Winter radish Black Spanish, Violet de Gournay

Daikon Bravo, Misato Rose, Green Luobo

Endive/escarole/catalogna De Meaux, Green Curled Ruffec

Brussels sprouts Jade Cross, Diablo

Lettuce Marvel of Four Seasons, Winter Density

Swiss chard, green-stemmed Verde de Taglio

Arugula Astro, Sylvetta

Beets Cylindra, Red Ace

Orach Orach Pink

Turnips, salad Hakurei, White Egg, Tokyo Market

Pak Choy* Tatsoi, Mei Qing Choi, Joi Choi

Radicchio Bel Fiore, Palla Rossa

Cabbage, standard Late Flat Dutch, Stonehead

Broccoli, standard Calabrese, Premium Crop

Cauliflower, standard Snowball, Violetta Italia

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Winter Vegetables (in decreasing order of cold hardiness)

Varieties (open-pollinated italicized)

Mache Vit, Verte de CambraiScallions Evergreen Hardy WhiteParsnips Harris Model, Hollow CrownAsian greens* Chinese Thick-Stem Mustard, SerifonCabbage, overwintering Deadon, Marabel, January KingSpinach, savoy types Tyee, Bloomsdale LongstandingKale, Scotch types Dwarf Blue Curled, WinterborLeeks, winter varieties American Flag, Blue Solaise, King SiegFava beans, small-seeded Diana, Sweet LoraneBroccoli, sprouting Matador, Santee, Early Purple SproutingGarlic Inchelium Red, Georgia FireCollards* Blue Max, ChampionRutabagas Laurentian, Purple Top, GilfeatherKale, Napus types Ragged Jack, Russian FrillsCauliflower, overwintering Galleon, MumblesAsian greens* Senposai, KomatsunaCarrots Napoli, Snow White, Danvers 126Turnips, roasting Golden Globe, Purple TopKohlrabi Early White Vienna, WinnerWinter radish Black Spanish, Violet de Gournay

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Mache (Corn Salad)

• $5 for only 3.5 oz in Krogers and Whole Foods!

• Very cold-tolerant – stays beautiful with minimum protection (Agribon-19 or GG17)

Baby Asian Greens and Kale• Salad Greens =

$5 - $6 per 8 oz bag

• Grown under AG-30 or GG34

Root Crops• $3-4 per bunch • Grown under AG-30 or GG34

(Hakurei turnips an exception)

Cabbage• $4-5 per head, with

leaves • Savoy and January

King types overwinter

Purple Sprouting Broccoli• continuous production

of broccoli florets beginning late March

April 2, 2012

Variety REALLY matters…

Purple 68 Napoli

Winter Growing:The Essential Elements

1. CHOOSING THE RIGHT PLANTS

2. CROP PROTECTION – Dessication is more damaging to plants than cold

temperatures – protect them from winds – Gro-Guard 34 (equivalent to Agribon 30) is

ideal – add additional layer when <15 F*

– no more clear plastic in production system to minimize labor (e.g., venting on clear days)

Low Tunnel Construction and Management

Low Tunnels made with 1/2” EMT

PVC vs EMT

• Cost comparable, but MAJOR difference in structural integrity

Bending EMT with a Johnny’s Selected Seeds’

Quick Hoops Bender ($59)

Low Tunnel Construction

Rebar isn’t required — use with caution!

Opening and Closing Low Tunnels

Row Cover is Gro-Guard Medium Weight (GG34) from Deerfield Supplies

Extra-Low Low Tunnels

Mini-hoops for salad greens

Space 2-3 ft apart for snow load readiness

Mini-hoops for salad greens

Winter Salad Mix = hardy Asian greens, mache, kale

High Tunnel $1.40 per ft2

EMT Low Tunnel $0.23 per ft2

x 2400 ft2 = $3360

x 2400 ft2 = $552

Replace plastic every 4 years = $0.20 per ft2

Replace cover* every 4(?) years = $0.03 per ft2

* = Polypropylene Fabric

Need low tunnels in high tunnels in extreme weather

Why low tunnels?Inexpensive!!!

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Cost Comparison for 4 ft X 50 ft bed (200 sq ft)

EMT Wire Hoops

Cost of Hoops 11 hoops @ $2.35 each$25.85

22 hoops @ $0.48 each$10.56

Cost of Row Cover $15.42 per 60 ft length X 2$30.84 $15.42

Sandbags 0.70 0.70

Total Cost $57.39($0.28 per sq ft)

$26.68($0.13 per sq ft)

($0.11/sq ft relative to high tunnel covered paths)

($0.23/sq ft relative to high tunnel covered paths)

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Why low tunnels?

Topography

Why low tunnels?

Snow Happens

Effect of snow cover on low tunnel temperatures

Snow

Ambient temperature

0 F

No snow cover

Why Low Tunnels?

Versatility

• hoops can be used to support insect barriers in spring/summer

• shade cloth support

Why Low Tunnels?Mobility

• Avoid accumulation of soluble salts

• At winter’s end, tunnels are easily moved to help other crops get an early start

• Cover crops (reduce dependence on compost/fertilizer)

Soil Fertility Matters: 50% of garden in cover crop in any given season

WINTER SPRING SUMMER FALL

Block 1 winter salad mix cover crop (Ph) cover crop (Ph) alliums & kale

Block 2 alliums & kale alliums & roots alliums & roots (B) roots

Block 3 roots cover crop (CS) cover crop (CS) cover crop (R,V)

Block 4 cover crop (R,V) cover crop (R,V) solanaceae roots & Asian greens

Block 5 roots & Asian greens

spring salad mix cover crop (H) cover crop (O,CC,F)

Block 6 cover crop (O,CC,F)

corn & beans corn & beans fall salad mix & peas

Block 7 cover crop (R,P) cover crop (CS) cover crop (CS) heading brassicas

Block 8 heading brassicas peas & potatoes cover crop (B) cover crop (O,CC,V,P,F)

Block 9 cover crop (O,CC,V,P,F)

cover crop (O,CC,V,P,F)

winter squash cover crop (R,V,P)

Block 10 cover crop (R,V,P) cover crop (R,V,P) sweet potatoes winter salad mix

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Why Low Tunnels?

• Reduced dependence on irrigation — row cover is somewhat permeable to water

• Jump start on spring planting with relatively drier beds

Why NOT Low Tunnels?• Areas subject to frequent

straight-line winds would be challenging

• Plant hardiness zone 5 and colder? Only try plants with greatest cold tolerance.

• Areas with continuous snow cover (tunnel access is difficult) or extended #nights in sub-zero temperatures

Winter Growing:The Essential Elements

1. CHOOSING THE RIGHT PLANTS

2. CROP PROTECTION – Dessication is more damaging to plants than cold

temperatures – protect them from winds – Gro-Guard 34 (equivalent to Agribon 30) is ideal

– add additional layer when <15 F*

3. DELAYING HARVEST – Plants must reach desired size before really cold

temperatures and less light arrive

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Goal: Have crops nearing maturity (or the size desired) near onset of

“Persephone Days”

Use days to maturity to count back from Persephone Days onset (+2-3 weeks

slower growth in fall)Enter the date of your latitude’s last 10 hour

day:

11/22

Crop Days to Maturity

Transplant? (1 = yes, 0 = no)

Target date to sow seed

(direct, or for transplants)

Target date to set transplants in field

Carrot, ‘Napoli’ 58 0 September 11 0

Broccoli, ‘Arcadia’ 63 1 August 9 September 6

Turnip, ‘Hakurei' 38 0 October 1 0

Brussel Sprouts, ‘Jade’ 120 1 June 13 July 11

Carrot 75 August 25 0

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb MarArugula :::: ::…. ^^^ ^^^ ^^^ ^ |Asian greens :::: ::::::: :…. ^^ ^^^ ^^^ ^^^ ^ |Beets :::….. .. ^^ ^^^ ^^^ ^^^ ^Broccoli, standard t tt TT ^^^ ^^^ ^Broccoli, sprouting t tt TT ^^^ ^^^ ^^^ ^^^ ^Broccoli raab (rapini) ::: ^^^ ^^^ ^^^ ^^^ ^Brussels sprouts tttt TT ^^ ^^^ ^Cabbage, Asian ::: ^^^ ^^^ ^^^ ^^Cabbage, heading t tt TT ^^^ ^^^ ^Cabbage, overwintering ttt tt TT ^^^ ^^^ ^^^ ^Carrots :: :::::… .. ^^^ ^^^ ^^^ ^Cauliflower, standard tttt t TT ^ ^^^ ^|Cauliflower, overwintering tttt t TT ^ ^^^ ^^^ ^^^ ^^^ ^Celeriac tt T TT ^^^ ^^^ ^| ttttttCollards :::::: ….. ^^ ^^^ ^^^ ^^^ ^Daikon :::: ::… ^^^ ^^^ ^^^ ^^^Endive/escarole/catalogna tt ..TT ^^^ ^^^ ^^^ ^^^ ^Garlic bbb bbGreens, specialty* :: :::…. ^^^ ^^^ ^^^ ^^^Kale :::::::: ::.…. ……. ^^ ^^^ ^^^ ^^^ ^Kohlrabi tt :::T T ^ ^^^ ^^^ ^^^ ^Leeks t tt T TT ^^^ ^^^ ^^^Lettuce :::::::. ……. .. ^^ ^^^ ^^^ ^^^ ^Mache ::: ::::… ^^^ ^^Mustard greens ::::: ::::… ^^ ^^^ ^^^ ^^^ ^Onions, bunching :::::Onions, perennial bbb bb

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Soil Temperatures for Germinating Vegetable SeedsMinimum (°F) Optimum Range (°F) Optimum (°F) Maximum (°F)

Bean, Fava 40 60-95 70 85Beet 40 50-85 85 95Broccoli 40 45-85 85 95Cabbage 40 45-95 85 100Carrot 40 45-85 80 95Cauliflower 40 45-85 80 100Celery/Celeriac 40** 40-75 70 80Chard, Swiss 40 50-85 85 95Collards 40 60-95 85 100Endive/Escarole 35 35-85 70 80*Kale 40 65-85 80 100Kohlrabi 40 65-85 80 90Leek 40 45-95 75 90Lettuce 35 40-80 75 85*Mache 40 40-70 68 70Mustard/Asian greens 40 45-85 80 100Onion 35 50-95 75 95Parsnip 35 50-70 65 85Pea 40 40-75 75 85Radish 40 45-90 85 95Radicchio/Chicory 45 45-85 70 85*Rutabaga 40 45-85 80 85Salsify/Scorzonera 40 65-75 70 -Spinach 35 50-70 65 85*Turnip 40 60-105 85 105Garden Under Cover: Winter Vegetable Production in Low Tunnels

Not all seeds are created equal.• There can be CONSIDERABLE differences in cold-hardiness in a given

variety from different companies.

• Find seed suppliers nearest your own climate

• colder climate seed sources aren’t always better

• be aware that some companies may source their seed elsewhere

• Patronize seed companies/growers that specialize in winter growing

• Johnny’s Selected Seeds, Osborne Seed Company, Adaptive Seeds, Wild Garden Seed, High Mowing Organic Seeds

• Even’ Star Farm (available via Southern Exposure Seed Exchange)

• Seed Savers Exchange Yearbook and local seed swaps

Why grow your own seeds?• Cost-savings?

• perhaps, depending on scale

• micro greens seed stock

• Control of seed supply

• kale seed shortage in 2014 and 2015

• seed no longer listed by company

• crop failure due to disease outbreak/GMO contamination in major seed hub (beets in Skagit Valley)

Choosing varieties for winter growing/seed saving

Least Profitable Most ProfitableBroccoli Collards Arugula Carrots

Brussels sprouts Kale (baby) Asian greens Kale (mature)

Cabbage Lettuce (baby) Beets Turnip

Cauliflower Mache Daikon/Winter Radish Rutabaga

Kohlrabi Parsnips Endive/Escarole

Onions, yellow Spinach Garlic

Swiss chard Leeks

Broccoli, sprouting Lettuce (mature)

Onions, bunching

Radicchio

Garden Under Cover: Winter Vegetable Production in Low Tunnels

Low Tunnel Management

• Heat is your enemy, not cold! – Tunnel temps >65° F shift plant cold tolerance

and promote disease • vent tunnels on warm sunny days, or completely

remove covers in warm stretches • Thicker row cover isn’t necessarily better – Light is equally important to temperature in

winter growing – heavier row covers limit transmission

Consider your area’s unique frost/freeze climatology

National Weather Service, Jackson, KY. http://www.weather.gov/jkl/frostfreezeclimo

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