Hoophouse in fall and winter Pam Dawling

The Hoophouse in Fall and Winter
©Pam Dawling 2015
Twin Oaks Community, Central Virginia
Author of Sustainable Market Farming
Published by New Society Publishers
SustainableMarketFarming.com
facebook.com/SustainableMarketFarming

What’s in this presentation
1. Overview of the hoophouse in fall and winter
2. Tables of cold-hardiness
3. Suitable crops for fall and winter
4. Scheduling
5. Tasks and challenges
1. Winter hoophouse tasks
2. Irrigation
3. Soil fertility, crop rotations
4. Cold weather pests
5. Persephone Days and Nitrate accumulation
6. Resources
7. My contact info

The hoophouse in fall and winter
We are amazed at how incredibly productive hoophouses are.
• Rate of growth of cold-weather crops is much faster inside
• Crop quality, especially leafy greens, is superb.
• Plants tolerate lower temperatures than outdoors; they recover in
the pleasant daytime condition. Salad greens in a hoophouse can
survive nights with outdoor lows of 14°F (–10°C). Add thick
rowcover and they can survive an outdoor low of -12°F (-24°C)
• Working in winter inside a hoophouse is much more pleasant
than dealing with frozen rowcovers and hoops outdoors.
• Get a hoophouse if you can. Get another!

Growing in the winter hoophouse
 Night-time protection of two
layers of plastic and an air gap –
big difference!
 Fall sowings thrive on sunny
winter days.
 When the daylight falls below ten
hours, growth slows down till
spring.
 In colder climate zones and
outdoors here, mature plants are
mostly being stored for harvest.
 For most of the winter, our zone 7
central Virginia hoophouse plants
are actively growing, so we
continue sowing new crops even
in December.
• Photo credit Wren Vile

Winter hoophouse crops
• Salad crops
• cooking greens
• Asian greens
• roots
• onions
• early peas, fava beans
• bare root transplants for setting outdoors in February &
March
Our hoophouse keeps night time temperatures about 7F
warmer than outdoors, sometimes 10F.
Plus, plants tolerate lower temperatures – it seems to be the
night+day average that counts.

Cold-hardiness table for hoophouse
crops – Frosty weather
Some starting numbers of outdoor killing temperatures, although
your results may vary. In the hoophouse (7F warmer than outside),
plants can survive 14F colder than outside without extra rowcover,
21F colder than outside with thick (1.25ozTypar/Xavan) rowcover.
• 35°F (2°C): Basil.
• 32°F (0°C): some pak choy, peppers, tomatoes.
• 25°F (–4°C): Chinese Napa cabbage, endive (hardier than lettuce,
Escarole more frost-hardy than Frisée), large leaves of lettuce
(protected hearts and small plants will survive even colder
temperatures), some mustards and Asian greens (Maruba Santoh,
mizuna, most pak choy, Tokyo Bekana), some onion scallions.
A test year: Lettuce and Mizuna survived a hoophouse
temperature of 10.4°F without rowcover, -2.2°F with.

Colder
• 22°F (–6°C): Some arugula, tatsoi (both have varieties
which survive much colder than this).
• 20°F (–7°C): Some beets, celtuce (stem lettuce), Tendergreen,
Tyfon Holland greens, radishes, turnips with mulch or
rowcover to protect them (Noir d’Hiver is the most cold-
tolerant variety).
• 15°F (–9.5°C): Some beets (Albina Verduna, Lutz
Winterkeeper), beet leaves, endive, fava beans (Aquadulce
Claudia), Russian kales, kohlrabi, Komatsuna, some lettuce,
especially small and medium-sized plants (Marvel of Four
Seasons, Rouge d’Hiver, Winter Density), parsley, Asian winter
radish (including daikon), large leaves of broad leaf sorrel,
turnip leaves, winter cress.
A test year: Lettuce, Mizuna, Turnips, Russian kales survived a
hoophouse temperature of 10.4°F without rowcover, -2.2°F with.

Colder still
• 12°F (–11°C): Some carrots (Danvers, Oxheart), most
collards, some fava beans, Senposai, some turnips
(Purple Top).
• 10°F (–12°C): chard (green chard is hardier than multi-colored
types), Belle Isle upland cress, some endive (Perfect, President),
perhaps Komatsuna, Asian winter radish (including daikon) with
mulch or rowcover for protection, large leaves of savoyed spinach
(more hardy than flat leafed varieties), most tatsoi, Yukina savoy.
For a complete list of cold-hardy crops indoors and out, see my
slideshow Cold-hardy Winter Vegetables on SlideShare.net
A test year: Lettuce, Mizuna, Turnips, Russian kales, Senposai, Tyee
spinach, Tatsoi, Yukina Savoy survived a hoophouse temperature of
10.4°F without rowcover, -2.2°F with. Brite Lites chard got frozen
leaf stems.

Coldest
• 5°F (–15°C): Some kale (Winterbor, Westland Winter, perhaps
Blue Ridge), some leeks (Bulgarian Giant, Laura, Tadorna),
some bulb onions (Walla Walla), smaller leaves of savoyed
spinach and broad leaf sorrel, a few unprotected lettuces if
small (Winter Marvel, Tango, North Pole, Green Forest).
• 0°F (–18°C): Chives, some collards (Blue Max, Winner), corn
salad, Vates kale (although some leaves may be too damaged
to use), Even’ Star Ice-Bred Smooth Leaf kale, a few leeks
(Alaska, Durabel), some onion scallions (Evergreen Winter
Hardy White, White Lisbon), salad burnet, salsify, some
spinach (Bloomsdale Savoy, Olympia, Tyee).
Remember these are outdoor temperatures. It’s warmer inside!

Which Crops are Most Profitable?
Some crops offer more money per area, some are more profitable
in terms of time put in.
Clifton Slade at Virginia State
University in his 43,560 Project
(how to earn $43,560 from one
acre), recommends choosing crops
which produce one vegetable
head or stalk, or 1 pound of
produce, per square foot. Leafy
crops feature prominently.
--------------------------------------------------------------------------------
Richard Wiswall Organic Farmer’s
Business Handbook
Leafy greens, parsley and basil
earned more than fruiting crops.
Michihili cabbage.
Credit Southern Exposure Seed Exchange

Which Crops Take Most Attention?
Steve Solomon in
Gardening When it Counts
provides tables of vegetable
crops by the level of care
they require.
His Difficult List includes
bulb onions, leeks, Chinese
cabbage, asparagus, celery,
celeriac, cauliflower,
Brussels sprouts, early
cabbage and cantaloupe.
Your results may vary!
Onion bed. Photo Kathryn Simmons

Reasons to Grow Crops That Don’t
Make the Highest Income
 provide a good crop rotation for your farm,
 provide diversity (customers will only buy so much
parsley and basil).
 provide for times of the year when fewer growers are
selling produce:
fall crops to harvest before serious cold,
crops for all-winter harvests,
early spring harvest markets with
overwintering crops.
Kohlrabi. Photo McCune Porter

Salad Crops
• Lettuce heads may
survive much colder
temperatures than you
ever imagined!
• Baby lettuce mix is
popular and easy
• Many cooking greens
can be used as salad
crops while plants are
small.
• Several small greens are
very winter-hardy.

Lettuce
Heat-tolerant varieties also tolerate cold. There are also
specialized cold-hardy varieties that do not tolerate heat
(because they have a relatively low water content). Sow these in
fall and winter only.
Lettuce germinates at 40°F–85°F (4°C–29°C). Optimum 75°F
(24°C)
Sow late afternoon/evening - better emergence than mornings.
Adolescent lettuce are more cold-hardy than full-sized plants.

Lettuce varieties for fall and winter
Particularly cold-hardy:
 Brune d’Hiver
 Cocarde
 Esmeralda
 Galactic
 Green Forest
 Hyper Red Wave
 Kalura
 Lollo Rossa
 North Pole
 Red Tinged Winter
 Rossimo
 Rouge d’Hiver
 Sunfire
 Tango
 Vulcan
 Winter Marvel
Rouge d’Hiver Lettuce
The Salad Bowls are not so good outdoors
in cold weather but do well in the
hoophouse. Icebergs do not survive frost.

Baby Lettuce
Lettuce Mixes Small-leaf lettuces: Osborne’s
Multileafs, Johnny’s
Salanovas, Tango, Oscarde,
Panisse. Photo credit Osborne Seeds
Lettuce Mix. Credit Twin Oaks Community

Asian-type brassica salad mixes
Wild Garden Pungent Mix,
Brassica juncea, (Wild Garden
Seeds, Fedco).
A cross of pungent Indian
mustards for those who like
Big Flavor. 40 days to harvest.
Photo credits Wild Garden Seeds
Pink Petiole Mix, Brassica
rapa (Wild Garden Seeds,
Fedco).
Fast-growing, cold tolerant,
adds a touch of color to the
brassica portion of winter salad
mixes. A varied mix of colors
and shapes. Ready in 40 days.

Mizuna/kyona
• Ferny leaves - add color and loft in
salad mixes
• Mild flavor
• Available in green or purple (but
Ruby Streaks is much better then
Purple Mizuna!)
• Regrows vigorously after cutting
• Use for baby salads after only 21
days
• or thin to 8"–12" (20–30 cm)
apart, to grow to maturity in 40
days
• Very easy to grow, tolerates cold
wet soil.
• Fairly heat tolerant (well, warm
tolerant)
• Cold tolerant to 25°F (-4°C)
Photo credit Ethan Hirsh

Ruby Streaks, Golden Frills, Scarlet
Frills, Red Rain
Johnny’s Red Splendor Ruby Streaks
Golden Frills

Other salad crops
• Sylvetta, Surrey and Astro
varieties of arugula are
particularly cold-hardy.
Even’Star arugula photo credit
SouthernExposure Seed Exchange
• Parsley, Belle Isle upland
cress, winter purslane,
salad burnet and mache
(corn salad) are also very
winter-hardy.
Belle Isle Upland Cress. Photo Credit Southern
Exposure Seed Exchange

Leafy cooking greens in the hoophouse
Brassicas and spinach are the most productive
crops in winter (more so than lettuce)
Night-time protection of two layers of plastic
and an air gap – big difference!
Photo credit Twin Oaks Community

Hardy cooking greens
• Spinach – we like Tyee and are trialing Abundant Bloomsdale
• Russian kales (better than Vates in the hoophouse). Most Napus
kales (Siberian and Russian) make faster growth during the low-light,
colder months of winter, compared to Oleracea kales like Vates. Many
Oleracea kales are more cold tolerant than napus sp., but they enter
a dormant phase and then bolt in early spring. Thanks Clara Coleman
• Swiss chard germinates best at 85°F (29°C) - useful as a substitute if
the fall is too hot to sow spinach. Fordhook Giant, Artgentata, Leaf
Beet are hardy varieties
• Senposai
• Other Asian greens
• Bright Lights chard. Credit Wren Vile

Asian Greens
• Grow particularly well in the
hoophouse, all winter in zone 7.
• Huge range of attractive
varieties
• Grow when you normally grow
kale
• Short spring season, bolt when
it gets hot
• Long fall season, no bolting.
Blues Napa Chinese cabbage
Credit Ethan Hirsh
 Green in Snow mustard (Shi-Li-Hon) is
reportedly the hardiest Asian green.
 In spring the order of bolting of Asian
greens is: tatsoi, pak choy, Komatsuna,
mizuna, leaf radish, mustards.

Advantages of Asian greens
 A quick way to fill out your
market booth or CSA bags
 A catch crop for spaces where
other crops have failed or
otherwise finished early. Keep a
flat of seedlings ready, pop plugs
into empty spaces as they occur.
 Better able to germinate in hot
weather than lettuce.
 Faster growing than lettuce
 Some of the faster-growing types
are ready for transplanting 2
weeks after sowing (or you can
direct sow them)
 Trial many kinds, use unwanted
seed in baby salad mix!

Healthful Diversity!
 Flavors vary from mild to
peppery - read catalog
descriptions before growing lots
 Colors cover the spectrum:
chartreuse, bright green, dark
green and purple.
 Nutritious as well as tasty.
 High in carotenoids, vitamins A
and C, calcium, iron, magnesium
and fiber.
 Help prevent high blood
pressure, heart disease and
stroke.
 Also contain antioxidants which
fight against cancer and protect
eyes from macular degeneration
Photo Credit Ethan Hirsh

Senposai - Our star of Asian greens
• Senposai is quite heat and cold
tolerant, a big plant with large,
round, mid-green leaves.
• Transplant it at 12"–18" (30–45
cm) spacing.
• Only 40 days to mature.
• Usually harvested leaf-by-leaf. It
can be very productive.
• Cooks quickly (much quicker
than collards), and has a
delicious sweet cabbagey flavor
and tender texture.
• A cross between komatsuna and
regular cabbage.
Senposai. Photo Ethan Hirsh

Komatsuna
• Also known as mustard spinach (as
Pak Choy is too!) and Summer Fest
• Green or red (purple)
• Baby salad size in 21 days, full size
in 35 days
• Grows into a large plant 18" (45
cm) tall
• Individual leaves can be picked and
bunched
• Or the whole plant can be
harvested
• The flavor is much milder than the
English name suggests - mildly
peppery
• Cold-tolerant to 15°F (-9.5°C),
perhaps 10°F (-12°C)
Photo credit Fothergill Seeds
Photo credit Fothergill Seeds

Napa and Michihili
Wong Bok Chinese cabbage
• Very tender, light green leaves
• Excellent for stir-fries and pickling.
• Hardy to about 25°F (–4°C)
• The cylindrical Michihili produces
16" (40-cm) tall heads 6" (15 cm)
across. Barrel-shaped Napa
cabbage produce less in the same
space.
• Michihili is more stress tolerant
and resistant to bolting and black
speck than Napa cabbage.
• Napa cabbage stores longer.
• We like Blues Napa cabbage (52
days from seed to harvest) and
Jade Pagoda (72 days) and the O-P
Michihili (72 days)
Photo credit Southern Exposure Seed Exchange

Celery cabbage, pe tsai:
Tokyo bekana and Maruba Santoh
Photo credit Johnnys Seeds
• Fast-growing, looseleaf, non-
heading vegetables with tender
chartreuse (yellow-green)
leaves and white petioles. Mild
flavor
• Can be harvested as baby leaves
after 21 days
• Or the leaves and wide white
stems of the mature plant
provide crunch for salads from
35 days after sowing.
• Or whole plants can be chopped
and lightly cooked
• More heat tolerant than Napa.
Cold tolerant to 25°F (-4°C).
Fairly bolt resistant

Pak choy/bok choi
• Sturdy white leaf stems, big green
leaves. Usually harvested as a
head 12"–15" (30–38 cm) tall
• 45–55 days to maturity
• Hardy down to 32°F (0°C), most
varieties to 25°F (-4°C)
• Can be picked as individual leaves,
for bunches of mixed braising
greens or stir-fry combinations
• We grow Prize Choy or Joy Choi
• There is also red choi (a 45-day,
red-veined baby leaf or maroon-
leaved full-size version)
• Photo credit Johnnys Seeds

More big Asian greens
 Tyfon Holland Greens - a strong
hybrid of komatsuna with a
heading brassica. Could be good in
a survival situation, or to grow for
goats. Hardy down to 20°F (-7°C).
 Tenderleaf – a big, sturdy, OP
plant. Quick-cooking, mild-
flavored, despite appearances.
Very disease-resistant . Cold
tolerant down to 20°F (-7°C). Can
be sown later in the fall than other
greens - could be the solution if
your original plan didn’t work. Can
be a useful salad mix crop at the
baby stage.
Mizspoona, Brassica rapa, a large
sturdy plant, 40 days to maturity. A
sweet flavor with a good balance of
mild zinginess. A gene pool (variable
plants). Mizuna crossed with Tatsoi.
Credit Wild Garden Seeds

Other big greens
• Chinese Thick-Stem Mustard (SESE,
Fedco, Even' Star Organic Farm,
Maryland). Multiple cuttings of balanced-
flavor salad mix crop to fill the CSA bags.
Extremely cold tolerant.
• Toraziroh, Brassica oleracea
algoblabria, a robust producer of high
yields of large leaves with a good, not
overpowering flavor. Related to Chinese
kale or Chinese broccoli. Relatively slow
to bolt, ready in 45 days

• Transplants of Red Giant Mustard
• Mature Red Giant Mustard
Photo credit Planet Natural
Mustard greens
Asian mustards such as Red Giant, Osaka Purple, and American Mustards (eg
Southern Green Wave) are hardy to light frosts. Attractive colors. 21 days to baby
leaves, 40–45 days full size

Tat soi/tah tsoi
• A small flat rosette of shiny,
dark green spoon-shaped
leaves, green-white stems
• 21 days for baby salads; 45
days for cooking
• Mild flavor, an attractive
appearance
• Very cold tolerant, hardy to
10°F (–12°C)
• Direct sow and then thin into
salad mixes, leaving some to
mature at 10" (25 cm) across
for cooking greens.
• Can transplant at 6" (15 cm)

Yukina Savoy
• like a bigger tatsoi,
• blistered dark green
leaves and stems
• delicious flavor
• about 12“ (30 cm) tall
• Tolerant to heat and cold
– down to 10°F (-12°C)
• Transplant at 12" (30 cm)
• 21 days to reach baby size,
45 days to full size

Small and/or short-lived crops
 Hon Tsai Tai (like a purple broccoli raab). Also known as
Choy Sum. Mostly stem with small clusters of buds. In
climates cooler than Zone 7 this might be productive in
the fall. For spring it could be a challenge most places. It
matures in only 35–40 days. Hardy to 23°F (–5°C).
Photo credit Johnnys Seeds
 Broccoli Raab We had the same trouble with this as with
Hon Tsai Tai
 Mei Qing Choi. A miniature 6" (15 cm) pak choy. These
might suit your market, but we do better with larger
vegetables. It matures in less than 45 days, a definite plus
 Vitamin Green/Bitamin-Na/Yokatta-Na A slender, white-
stemmed plant, about 12" (30 cm) tall. It can be planted
4" (10 cm) apart, or direct sown and thinned. Tolerates
heat and cold. Quick-growing with good flavor, not
pungent: 21 days for salad mix, 45 to its full size

Roots: Turnips
Turnips do very well in the winter
hoophouse. We sow our first ones
Oct 15 (around our first frost date)
for harvest from Dec 4. We like Red
Round and Hakurei and have tried
out Oasis and White Egg to find a
cheaper replacement for Hakurei
(Oasis is the closest). We do a
second sowing Nov 9 and a small
third sowing Dec 10.
Scarlet Ohno Revival turnip
White Egg turnip.

Carrots
• Carrots prefer soil
temperatures of 45°F–85°F
(7°C–29°C),
• They germinate in 6 days at
80°F (27°C), their optimum.
• Keep the soil surface damp
until they come through.
• Varieties suitable for winter
hoophouses include
Napoli, Nelson, Mokum and
Rainbow Mix

Beets
• Beets prefer soil temperatures of 50°F–85°F
(10°C–29°C)
• Only 3.5 days to emerge at 86°F (30°C), but
14.6 days at 50°F (10°C).
• Hand-sowing pre-sprouted seed is an option
if the soil is too hot when you need to make
fall sowings.
• Sow 1/2″-1″ deep, tamp the soil, and keep
the surface damp with daily watering until
they emerge.
• Varieties suitable for winter hoophouse use
include Bulls Blood (for beautiful leaves),
Babybeat (small, perfectly formed round
beets).
Crosby Egyptian Beet. Credit Southern Exposure Seed Exchange

Radishes
Easter Egg radishes. Photo credit Southern
Exposure Seed Exchange • Varieties that work well
for us: Easter Egg
(multicolored), White
Icicle, and Cherry Belle
• Sparkler got too fibrous
for us, as did Cherry
Belle after mid October
• We make 6 sowings of
radish between 9/6 and
1/26

Onions
Scallions
• We sow 9/6 for harvest
12/1 - 3/1 and 11/18
(following radishes) for
harvest in early spring
Bulbing onions
• We sow for growing to
maturity in the hoophouse
• We also grow seedlings for
planting outdoors.
Onion photo credit Kathryn Simmons

Peas and beans
Fava beans sown 11/15 and
harvested mid-May.
Photo credit Kathryn Simmons
Dwarf snap peas (sown 2/1)
Photo credit Kathryn Simmons

Bare-root transplants
• Plants dug up from a nursery
seedbed and transplanted
elsewhere.
• Save time and money,
compared to growing starts
in flats.
• Save on greenhouse space.
• Very sturdy plants - full
depth of soil to develop big
roots
• Little extra care needed -
less prone to drying out than
seedlings in flats.
In October we sow “filler”
greens and lettuce to use in the
hoophouse during the winter
In November we sow bulbing
onions to plant outdoors 3/1
Jan 24 we sow kale, collards,
spinach to plant outdoors in Mar.

Making a co-ordinated schedule
 Make a map of the bed
layout and plan the area
each crop will occupy.
 Decide on planting
dates
 Calculate harvest dates,
and plan follow-on
crops where possible.
 Draw up a planting
schedule in date order

Days to Maturity
 ‘Days to maturity’ in catalogs are generally for spring planting once conditions
have warmed to the usual range for that crop. When growing late into the fall,
add about 14 days for the slowdown in growth.
 It usually means ‘Days to First Harvest’ which may not be the same as ‘Days to
Full Harvest’.
 With carrots it exact size doesn’t matter, but an unheaded Chinese cabbage is no
good.
 With CSAs, you can distribute Pak Choy to some sharers one week, and others
the next.
 If it’s important to have a plentiful harvest when you do start, add another 7-14
days.
Carrot photo
Kathryn Simmons

Scheduling spinach and chard
• Spinach is a challenging crop to start in hot weather!
• Optimum germination temperature 70°F (21°C) Max
85°F (29°C). Wait for soil temperature to drop.
• For earlier planting, pre-sprout seeds one week. We
sow sprouted spinach 9/6 or so in our hoophouse.
• Swiss chard germinates best at 85°F (29°C), so
consider that as a substitute for a first sowing if the
fall is impossibly hot.
Tyee spinach. Credit Kathryn Simmons

Scheduling Beets
• Sow beets dry or soaked for 1-2 hours in a little water. (Don’t soak
too long, or in a lot of water – beet seeds are easy to drown.) We
usually sow pre-soaked by hand. Sometimes dry with the EarthWay
chard plate 2 passes.
• We sow Bulls Blood beets 9/7 to use the tops in salad mixes
• For early spring eating, sow Ace in 72 plug trays in mid Oct,
transplant them in the hoophouse and harvest from mid-March.
We are trying a new variety from Johnny's called Babybeat, seeded
in February, for harvesting late April.
• We sow Cylindra beets 2/15 for a late spring crop
Photo Detroit Dark Red Beet.

Fall Hoophouse Planting - September
 Early September : We clear and add
compost to one of the beds and sow
sprouted spinach seed, radishes,
scallions, Bulls Blood beet greens
and tatsoi.
 Sept 15 and Sept 24: We make
outdoor sowings of crops to later
transplant into the hoophouse at 2–4
weeks old. See next slide.
 At the end of September we clear
summer crops from one more bed,
add compost and work it in. We
transplant Tokyo Bekana and
Maruba Santoh at 2 weeks old,
Chinese cabbage, pak choy and
Yukina Savoy at 3 weeks.
Photo November hoophouse beds.
Ethan Hirsh

Fall outdoor sowings to transplant inside
• Sept 15: about ten varieties of hardy leaf lettuce and
romaines, pak choy, Chinese cabbage, Yukina Savoy,
Tokyo Bekana, Maruba Santoh, chard.
• Sept 24: another ten varieties of lettuce, Red and White
Russian kales, Senposai, more Yukina Savoy, mizuna and
arugula.
• We use hoops and ProtekNet, and water frequently.
Senposai. Credit Kathryn Simmons

Fall Hoophouse Planting - October
 By mid-October we clear and
prepare another bed and
transplant lettuce at 10" (25 cm)
apart, and chard.
 Oct 15 we sow our first turnips.
 Sow Ace beets in 72 plug trays in
mid Oct, transplant them and
harvest from mid-March.
 Late October we sow more “filler”
greens, baby lettuce mix, our
second spinach, turnips and
chard, and more radishes.
 In the fourth week of October, we
clear and prepare more beds and
transplant the Senposai, mizuna,
the 2nd lettuce, kale, arugula and
Yukina Savoy at 4 weeks old.
Mizuna Photo credit Ethan Hirsh
Early October, we sow more
radishes and some “filler” greens,
(spinach, lettuce and Asian
greens) to fill gaps later. We try
hard to keep all the space
occupied, mostly using lettuce and
spinach.

Hoophouse Planting –
November and December
 Nov 10 we sow more turnips, mizuna
and arugula, more filler lettuce and
spinach, and our first bulb onions for
field transplanting as early as possible in
the new year.
 Nov 11-20 we sow scallions, tatsoi,
radishes, more bulb onion starts.
 From Nov 10 on we aim to keep a fully
planted hoophouse, and as each crop
harvest winds down, we immediately
replace that crop with another.
 During December we use the “Filler”
greens plants to replace casualties and
heads of Chinese cabbage, Pak choy,
Yukina Savoy each day as soon as we’ve
harvested them. Pak Choy replacing
Yukina Savoy here. Credit Ethan Hirsh

Gather sowing and
harvest start dates
and draw graphs
 Using your data, plot a graph for
each crop, with sowing date along
the horizontal (x) axis and harvest
start date along the vertical (y) axis.
 Mark the first possible sowing date
and find the harvest start date for
that.
 Decide the last worthwhile harvest
start date, mark that.
 Then divide the period into a whole
number of segments, according to
how often you want a new patch.
Cherry Belle radishes. Credit Southern
Exposure Seed Exchange

Winter hoophouse radish succession
cropping graph
A work-in-progress! See my slide
show on Succession Planting for
Continuous Vegetable Harvests on
SlideShare.net

Daily hoophouse tasks in winter
• Two hours work each day in winter in our 96’ x 30’ tunnel.
• Keep the temperature in the 65°F–80°F (18°C–27°C) range during the day, opening
the big high windows, and the doors as needed. If the sun is shining we usually open
the windows around 9 am and close them around 2:30 pm (a few hours before dark)
to store some of the warmth. Windows open above 40°F, doors above 50°F outside.
• Even in cold weather, plants need fresh air! High-density cropping can really use up
the carbon dioxide in a closed hoophouse very quickly. When this happens,
photosynthesis crashes and plant growth becomes limited. Soil high in organic
matter contains high levels of organisms that produce carbon dioxide. Dense plant
canopies can trap this near soil level, where it is most useful.
• Our main task each day is harvesting. In the winter of 2009–2010, we had frozen soil
or snow on the ground outside for a month (very unusual for us). Despite this we
were able to keep a hundred people in fresh salad and cooking greens (with turnips
and scallions for variety) for the whole month.
• Aside from harvesting, jobs include planting new crops, clearing old ones, spreading
compost, hoeing, hand weeding and supplying water as needed.
• We have drip irrigation. In the middle of winter, not much water is needed, and we
try to only water when a relatively mild night is forecast.

Winter hoophouse harvest dates
• November onwards: spinach, lettuce leaves, mizuna,
arugula, beet greens, tatsoi and brassica mix for
salad, radishes and scallions.
• From December: baby lettuce mix, Tokyo Bekana,
Maruba Santoh, chard, kale and turnips. Kale grows
whenever it is above 40°F (5°C).
• January till mid-March; the bigger greens, including
Senposai, pak choy, Chinese cabbage and Yukina
Savoy, lettuce heads.
• Yukina savoy. Credit Ethan Hirsh

Winter harvesting techniques
Don’t harvest frozen crops.
With baby salad mixes, highest productivity is
from “Cut and Come Again” crops — the tops
of the plants above the growing point are cut
with scissors or shears every 10–35 days.
Leaf-by-leaf is the method we use for kale,
collards, chard and spinach. We harvest lettuce
by the leaf, leaving the center to keep growing,
and switch to harvesting the heads in late
January, when growth begins to pick up.
Don’t harvest too much — we say “8 for Later”
meaning leave at least the inner 8 leaves.
Whole plant harvesting works well for small
plants like tatsoi and corn salad. A direct-
seeded row can be thinned over time by
harvesting out the biggest plants on each visit.
Tatsoi. Credit Wren Vile

Harvesting
 Some crops are harvested as
whole heads; others can be
harvested by the leaf and
bunched or bagged.
 The open rosette types, such as
tatsoi or the bigger Yukina Savoy,
are usually gathered closed and
banded with plant ties or rubber
bands.
 Most Asian greens can be grown
for baby salad mix.
 With mizuna we do a “half buzz-
cut,” snipping off leaves on one
half of the plant an inch (25 mm)
above the ground each time we
come by.
Tat soi shown here. Credit Ethan Hirsh

Growing winter crops may involve
sowing when soils are hot
1. Consult the tables in Nancy Bubel’s New Seed Starter’s Handbook
or Knott’s Vegetable Grower’s Handbook, on the germination
requirements for your crop, and the expected time to emergence
under your field conditions – and use a soil thermometer.
2. If soil temperatures are too high for good germination, cool a
small part of the outdoors:
– Shade from other plants, shadecloth, boards, burlap bags,
– For crops you normally direct seed, consider cooling a small
nursery bed for your seedlings and transplanting later.
3. If outdoors is impossible, start seeds indoors:
– Put a plastic flat of lettuce in your refrigerator or a cool room.
– Use plug flats or soil blocks rather than open flats, to reduce
transplant shock.

Irrigation
 Need plenty of water to grow
pleasant-tasting leaves.
 1” (2.5 cm) of water per week is
often enough
 During very hot weather, 2” (5
cm) is better
 Drip irrigation saves water and
reduces disease and weed
pressure.
 In summer, the faster growing
types of Asian greens are ready
to plant out 2 weeks after
sowing. Napa cabbage, Tokyo
Bekana and Maruba Santoh are
in this category.
 Most others transplant best at
3–4 weeks of age (less time than
needed in spring).

Water is Vital for Transplants!
Damp soil is important before,
during and after transplanting.
Water your plants an hour before
transplanting, and then also well
after planting. If necessary, in very
dry weather, water the soil ahead
of planting.
Use drip tape with emitters at the
chosen crop spacing, water for
twenty minutes before planting,
and then plant directly into the
wet spots. No other measuring is
needed.
Water the transplants the next day,
on days three, seven and ten after
planting, and then weekly after
that.
Senposai. Photo credit Ethan Hirsh

Compost is Central to our Soil
Fertility Program
• One of our community businesses is making and selling
tofu. Okara is a high-nitrogen waste product from tofu
making, the part of the soybeans that doesn’t go into the
soymilk.
• We mix in high-carbon sources such as sawdust (waste
from our hammock-making business) or woodchips that we
trade for with a neighbor.
• We also add kitchen scraps from our dining hall,
• and sometimes weeds or crop refuse from our garden. In
the summer we don’t collect up the weeds, just let them
die in place, as that is easier.
• We don’t have specialized compost-turning machines or
screens. We use the tractor bucket to lift and turn the piles.

Finished Compost
Finished compost ideally has a C:N
(carbon:nitrogen) ratio of 10:1.
If the C:N ratio is greater than about 25:1,
almost no nitrogen is available from the
compost and it is unable to mineralize.
Between 16 and 20:1, about 10 percent of the
N is available.
Even at a C:N ratio of 10:1, only half of the
nitrogen is available in the near term.

How Much Compost?
 In his Winter Harvest Handbook, Eliot Coleman
recommends 5 gallons/ 25 ft2 or 15 tons/acre (8.6 l/m2) of
raised beds, for each successive crop.
 Compost improves the soil structure, organic matter and
humus.
 Effects last longer than cover crops and crop residues,
especially in humid conditions where the breakdown of
plant material is very rapid.
 Compost can add a range of beneficial bacteria and fungi,
which can inoculate plants against diseases by inducing
systemic acquired resistance. The plants produce
antibodies and other protective compounds before any
infection can occur.

Crop Rotations
• We work out an ad-hoc plan for each year, juggling
rotation, timing, height and shading.
• We don’t repeat the same crop family two years
running: lettuce, brassicas, spinach/beets/chard.
• Because everything happens faster in a hoophouse,
we are growing multiple crops in each bed each year.
• We look at the sequence of crops, rather than the
number of years since the same crop was grown.
• We hope that the part of the year spent growing
other crops contributes to a speeded up version of
the time needed away from that crop in an outdoor
rotation.

Pests
Credit ipm.ncsu.edu
In cooler weather, our worst
hoophouse pests are aphids
and vegetable weevil larvae.
• We spray the aphids with
soap 3 times, 5 days
apart, or later in the
season we bring in
ladybugs.
• VWL live in soil, come out
at night to eat holes in
brassica leaves. We killed
them with Spinosad.

Persephone days and
scheduling winter
hoophouse crops
• When the daylight is shorter than 10 hours a day not much growth
happens. The dates depend on your latitude.
• In Central Virginia, latitude 38° North, this period lasts two months,
from November 21 to January 21.
• Soil temperature also matters. December 15-February 15 is the
slowest growing time for us.
• To harvest in the darkest days of winter you’ll need to plan a good
supply of mature crops to take you through. What has already grown
before this period will provide most of your harvests.
• For most of the winter, our hoophouse plants are actively growing,
not merely being stored for harvest (as happens in colder climate
zones and outdoors), so we can continue sowing new hoophouse
crops even in December and January.

Minimizing nitrate accumulation in
winter
In winter, when light levels are low, beware of high levels of
nitrates in leafy greens.
A health hazard — nitrates can be converted in the body into
nitrites, which reduce the blood’s capacity to carry oxygen and
may be further converted into carcinogenic nitrosamines.
Photo credit
Kathleen
Slattery

Nitrate accumulation
• Plants make nitrates during the night, and convert them
into leaf material during the day.
• It takes about six hours of sunlight to use up a night’s
worth of nitrates.
• In winter, a small handful of leafy vegetables can exceed
the acceptable daily intake level of nitrate for an adult,
unless special efforts have been made to reduce the
levels.

To keep nitrate levels as low as possible:
 Grow varieties best suited for winter;
 Avoid animal fertilizers; use organic compost.
 Ensure soil has sufficient P, K, Mg and Mo
 Water enough but not excessively;
 Provide fresh air as soon as temperatures reach 68°F (20°C),
so that carbon dioxide levels are high enough;
 Harvest after at least four (preferably six) hours of bright
sunlight in winter;
 Avoid harvesting on very overcast days;
 Avoid over-mature crops and discard the outer leaves. Harvest
crops a little under-mature, rather than over-mature;
 Refrigerate immediately after harvest, store harvested greens
at temperatures close to freezing;
 Use crops soon after harvest;
 Mix your salads; don’t just eat spinach.

Resources – General
ATTRA attra.ncat.org:
 Market Farming: A Start-up Guide,
 Scheduling Vegetable Plantings for a Continuous Harvest,
 Season Extension Techniques for Market Farmers.
 Cole Crops and Other Brassicas: Organic Production
 SARE www.sare.org A searchable database of research findings:
 Season Extension Topic Room
 extension.org/organic_production The organic agriculture community with
eXtension. Publications, webinars, videos, trainings and support. An
expanding, accessible source of reliable information.
 Growing Small Farms: growingsmallfarms.ces.ncsu.edu/ Debbie Roos keeps this
site up to the minute. Click Farmer Resources
 Penn State Extension High Tunnels site:
extension.psu.edu/plants/plasticulture/technologies/high-tunnels
 HighTunnels.org: hightunnels.org/category/for-growers/growing-in-high-
tunnels Lots of info, also a Listserve.

Resources - slideshows
Many of my presentations are available at www.Slideshare.net. Search for Pam
Dawling.
 Cold-hardy Winter Vegetables
 Producing Asian Greens
 Production of Late Fall, Winter and Early Spring Vegetable Crops
 Succession Planting for Continuous Vegetable Harvests
Other slide shows I recommend:
 Alison and Paul Wiediger : www.slideshare.net/aunaturelfarm/high-tunnel-1-
why-grow-in-high-tunnels and at least 11 more.
 Mark Cain Planning for Your CSA: www.Slideshare.net (search for Crop
Planning)
 Tom Peterson Farm Planning for a Full Market Season
vabf.files.wordpress.com/2013/02/tom-peterson-farm-planning-for-a-full-
market-season.pdf
 Brad Burgefurd, Cultural Practices And Cultivar Selections for Commercial
Vegetable Growers. www.slideshare.net/guest6e1a8d60/vegetable-cultural-
practices-and-variety-selection

Resources – books and seeds
 Walking to Spring, Using High Tunnels to grow produce 52 weeks a year, Alison
and Paul Wiediger
 Knott’s Handbook for Vegetable Growers, Maynard and Hochmuth
 The New Seed Starter’s Handbook, Nancy Bubel, Rodale Books
 The New Organic Grower, Eliot Coleman, Chelsea Green
 Grow Your Own Chinese Vegetables, Geri Harrington, 1984, Garden Way
Publishing. Includes the names for these crops in different cultures.
 Growing Unusual Vegetables, Simon Hickmott, 2006, Eco-Logic books, UK.
 Oriental Vegetables: The Complete Guide for the Garden
and Kitchen, Joy Larkham, revised edition 2008, Kodansha, USA
 Wild Garden Seeds www.wildgardenseed.com
 Even ‘Star Farm http://www.localharvest.org/even-star-organic-farm-M9994
specialize in cold-tolerant varieties.
 Evergreen Seeds’ helpful clickable list of Asian greens:
http://www.evergreenseeds.com/asveglis.html

Hoophouse in fall and winter Pam Dawling

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