Cold-Hardy Winter Vegetables Guide

Cold-Hardy Winter Vegetables
©Pam Dawling 2017
Twin Oaks Community, Virginia
Author of Sustainable Market Farming
Published by New Society Publishers
SustainableMarketFarming.com
facebook.com/SustainableMarketFarming

I live and farm at Twin Oaks Community, in central Virginia.
We’re in zone 7, with an average last frost April 30 and average first frost
October 14. Our goal is to feed our intentional community of 100 people with a
wide variety of organic produce year round.

What’s in this presentation
• Why would you farm in winter?
• Winter-kill temperatures of various crops
• Four ranges for cold-hardy crops
• Examples of suitable crops
• Scheduling outdoor crops
• Hoophouse growing in winter
• Winter storage of vegetables
• Resources
• My contact info

Why grow winter vegetables?
People eat all year long!
The locavore movement
is growing.
Winter share CSAs are
more in demand
Keep your customers,
Keep your crew,
Keep in shape!
It’s easier than the
summer - fewer crops to
care for
Weeds grow slower.

Before taking the plunge into winter
growing
Know your goals,
know your climate,
know your resources,
know your market,
know your crops (the main
focus of this presentation),
when you don’t know, experiment on a
small scale.

Cold Weather Crop Protection
Four basic levels of protection:
1. Rowcover
2. Quick Hoops and Caterpillar
Tunnels
3. Hoophouses (High Tunnels)
4. Heated greenhouses
Rowcover
• Use rowcover to keep frost-tender
crops alive and productive beyond
the first few fall frosts, and to keep
hardy crops alive in winter.
• Lightweight, easy to use, easy to
store.
• Hold down edges with bags of rocks
or sand, plastic jugs of water, or
metal or wooden stakes lying along
the edges.Photo Kathryn Simmons

Rowcover
 To protect against cold, you need thick
rowcover.
 Dupont Xavan 5131 (aka Typar). 1.25 oz/sq
yd spunbonded polypropylene; 75% light
transmission; about 6 F (3.3 C) degrees of
frost protection; can last for 6 years or more.
 Thinner types are to protect from insects -
can be doubled up for cold weather.
 Agribon 17 (or 19), 0.55 oz/sq yd spun-
bonded polypropylene; transmits 85% of
light; offers 4F (2.2C) degrees of frost
protection.
We think polypropylene rowcover lasts longer and is tougher than polyester (Reemay)
• Hoops keep
rowcover from
sticking to frozen
leaves and reduce
abrasion.
• 9- or 10-gauge wire.
• In winter we use
double wire hoops

Quick Hoops and Caterpillar Tunnels
Quickhoops
• Cover more than one bed, close to
the ground.
• Can be covered with rowcover
topped by hoophouse plastic for the
winter.
• Or, once plants are established, if
they can withstand cold nights, they
may benefit more from clear plastic
instead of rowcover over hoops.
Photo Johnnys Seeds
Caterpillar tunnels
• Usually tall enough to walk in
• Sometimes narrower than
Quickhoops. 2 beds + 1 path
• Plastic or rowcover held down by
ropes at each hoop.
• Can be used for summer or winter.
• No sandbags.
Photo MOFGA

Hoophouses or High Tunnels
• We are amazed at how incredibly productive hoophouses are.
• Hoophouses use one or two layers of plastic
• Double-layer houses use a small electric blower to inflate the gap
• A double-layer house provides about 8F (4.5C) degrees of night-
time temperature difference
• Rowcovers can be used inside for extra cold protection
• Working in winter inside a hoophouse is much more pleasant than
dealing with frozen rowcover and hoops outdoors.

Heated Greenhouses
• Greenhouses are great places to start your own transplants –
especially with a heated area for germinating seedlings
• The cost of heating may not be worthwhile for growing crops to
maturity. Buy several hoophouses for the price of one greenhouse
and heating
• Heat is only one aspect of growing plants – daylength and sunlight
intensity are also important.
• Aphids and whiteflies can quickly become problems in heated
spaces.

Winter-Kill Temperatures –
Frosty Weather
35° to 25°F (2°C to -4°C)
Some starting numbers of killing temperatures outdoors.
In the hoophouse (8F warmer than outside) plants can survive 14F
colder than outside, without extra rowcover;
21F colder than outside with rowcover (1.25ozTypar/Xavan).
See the handout for variety names.
• 35°F (2°C): Basil.
• 32°F (0°C): Cucumbers, eggplant, melons, okra, peppers, tomatoes.
• 27°F (–3°C): Some cabbage, Sugarloaf chicory.
• 25°F (–4°C): Some cabbage, chervil, chicory roots for chicons and
hearts, Chinese Napa cabbage, dill, endive (Escarole more frost-
hardy than Frisée), some fava beans (Windsor), annual fennel, some
Asian greens (Maruba Santoh, mizuna, most pak choy, Tokyo Bekana),
some onion scallions, radicchio.

Colder
from 22°F down to 15°F
• 22°F (–6°C): Arugula, (may survive colder than this),
large leaves of lettuce (protected hearts and small plants
will survive even colder temperatures), rhubarb.
• 20°F (–7°C): Some beets, some cabbages (outer leaves may be
damaged), celeriac, celtuce (stem lettuce), some head
lettuce, some mustards/Asian greens (Tendergreen, Tyfon
Holland greens), flat-leafed parsley, radishes, most turnips.
• 15°F (–9.5°C): Some beets, beet greens, some broccoli, some
cabbage, celery with rowcover, red chard, cilantro, endive,
some fava beans (Aquadulce Claudia), Russian kales, kohlrabi,
some lettuce, especially small and medium-sized plants, curly
parsley, rutabagas, broad leaf sorrel, turnip leaves, most
covered turnips, winter cress.

Colder still
down to 10°F
• 12°F (–11°C): Some beets, broccoli, Brussels sprouts,
some cabbage, carrots, most collards, some fava beans,
large garlic tops, most fall varieties of leeks, large tops
of potato onions, covered rutabagas, Senposai leaves
(the core of the plant may survive 10F), some turnips.
• 10°F (–12°C): Covered beets, purple sprouting broccoli
for spring harvest, a few cabbages, chard (green chard
is hardier than multi-colored types), Belle Isle upland
cress, some endive, young stalks of bronze fennel, Blue
Ridge kale, Komatsuna, some leeks, some covered head
lettuce, covered Asian winter radish (including daikon),
large leaves of savoyed spinach (more hardy than flat
leafed varieties), tatsoi, Yukina Savoy.

Coldest
down to 0°F
• 5°F (–15°C): Garlic tops even if small, some kale, some
leeks, some bulb onions, potato onions and other
multiplier onions, smaller leaves of savoyed spinach and
broad leaf sorrel, many Even’ Star Ice Bred greens varieties
are hardy down to 6°F (-14°C), unprotected small lettuces.
• 0°F (–18°C): Chives, some collards (Blue Max, Morris
Heading, Winner), corn salad (mâche), garlic, horseradish,
Jerusalem artichokes, Even’ Star Ice-Bred Smooth Leaf kale,
a few leeks (Alaska, Durabel), some bulb onions, some
onion scallions (Evergreen Hardy White, White Lisbon),
parsnips, salad burnet, salsify, some spinach (Bloomsdale
Savoy, Olympia).

Unthinkably Cold
• -5°F (-19°C): Leaves of overwintering
varieties of cauliflower, Vates kale survives
although some leaves may be too damaged to use.
• -10°F (-23°C): Reputedly, Walla Walla onions sown
in late summer
• -30°F to -40°F (-34°C to -40°C): Narrow leaf sorrel,
Claytonia and some cabbage (January King?) are
said to be hardy in zone 3
• Use this table to decide what to grow and when to
harvest it.

Four situations
1. Cool weather spring/fall crops to
harvest before very cold weather
(see my slideshow Fall Vegetable Production for
more on these crops)
2. Crops to keep alive as far into winter
as possible
3. Hardy winter-harvest crops
4. Overwinter early spring-harvest
crops

1. Cool weather spring/fall crops
• beets, carrots,
• chard, spinach,
• lettuce, salad mix,
• Asian greens,
cauliflower,
• turnips, rutabagas,
• cabbage, broccoli,
• kale, collards, kohlrabi,
• radishes (large and
small)
• scallions
Bed of young Danvers carrots.
Credit Kathryn Simmons
For details, see my slide show
Fall Vegetable Production
on SlideShare.net

Scheduling cool weather fall crops
With fall crops, even a difference of 2 days in sowing
dates can make a difference of 2-3 weeks in harvest
date, because plants grow slower as days get shorter
and cooler.
The “Days to maturity” listed in catalogs is usually for
spring conditions. Plants may mature faster in warm
fall soils or slower once the weather cools.
Danvers 126 carrots.

Broccoli and cabbage
It’s really worth growing fall brassicas
because as they mature in the cooler
fall days they develop delicious flavor.
The most challenging part of growing
fall brassicas is getting the seedlings
growing well while the weather is hot.
Unlike some cool-weather vegetables
such as spinach, brassicas actually
germinate very well at high
temperatures: the ideal is 77°F–85°F
(25°C–29°C), but up to 95°F (35°C)
works.
Weeds and pests slow down — once
established these crops need little
care.
Cabbage bed, credit McCune Porter

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.
Rowcover will provide a temperature gain of 4–6 degrees F
(2.2–3.3 degrees C), depending on the thickness. It also
reduces light transmission and airflow, but the trade-off can be
very worthwhile.
Lettuce may survive an occasional dip to 10°F (–12°C) with
good rowcover — but not 8°F (–13°C), I can tell you!
Adolescent lettuce are more cold-hardy than full-sized plants.

2. Crops to keep alive as far into
winter as possible
Many greens and roots can
survive some freezing, so it
is worth experimenting to
find how late you can keep
crops outdoors.
Use the table to get an idea
of what to expect.
Radishes die at 20°F (–7°C )
Cherry Belle Radishes.
Credit Southern Exposure Seed Exchange.

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

Cold-hardy Asian Greens
Tatsoi/tah tsoi
• Small, flat rosette of shiny, dark
green spoon-shaped leaves and
white stems
• Mild flavor, attractive appearance,
easy to grow
• Extremely cold tolerant, hardy to
22°F (–6°C) or colder
• Can direct sow and thin into salad
mixes, leaving some to mature at
10" (25 cm) for cooking greens.
• Can transplant at 6" (15 cm)
• Kitazawa Seeds have a Red Violet
tatsoi, with an upright habit
• Takes 21 days to baby salad size
• 45 days to reach cooking size
Yukina Savoy
• Like a bigger tatsoi, 12“ (30 cm) tall
• Blistered dark green leaves, greener
stems and delicious flavor
• Both heat and cold tolerant
• Can transplant at 12" (30 cm)
• Needs 21 days to reach baby size,
45 days to full size
Tatsoi, Yukina Savoy,
Credit Ethan Hirsh
In spring the order of bolting of Asian greens is:
tatsoi, pak choy, Komatsuna, mizuna, leaf radish, mustards.

Yukina Savoy Outdoors in December
After several nights at 16-17°F (-8 to -9°C)

More Cold-hardy Asian Greens
Komatsuna - also known as mustard
spinach and Summer Fest. Green or red, a
large cold-tolerant 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. Baby salad
size in 21 days, full size in 35 days;
Senposai is quite heat and cold tolerant, a
big plant with large, round, mid-green
leaves. Usually harvested leaf-by-leaf. It
can be very productive. Transplant it at
12"–18" (30–45 cm) spacing. Cooks
quickly (much quicker than collards), and
has a delicious sweet cabbagey flavor and
tender texture. It is a cross between
komatsuna and regular cabbage. It takes
only 40 days to mature.
Senposai. Photo Ethan Hirsh

Senposai in November –
the young hoophouse crop is almost ready to
take over from the well-used outdoor crop.

Turnips and rutabagas
Rutabagas can be stored in the
ground (unlike turnips, except in
warm climates). Mulch over them
with loose straw once the
temperatures descend near 20°F (–
7°C).
Turnips do very well in the winter
hoophouse. We also grow Purple
Top White Globe outdoors in spring
and fall.
White Egg turnip.

3. Cold-hardy crops to harvest in
winter
• spinach
• kale
• collards
• cabbage
• leeks
• carrots
• parsnips
We grow our winter-harvest
crops in our raised bed area,
which is more accessible in
winter and more suited to
small quantities.
Deadon cabbage. Credit Johnny’s Seeds

Use the Winter-kill temperature chart for
crops that will survive your lowest
temperatures, taking any crop protection into
account.
Add some wind protection, if you can.
Look for the hardiest varieties. At our Zone 7
farm, we overwinter Vates kale without
rowcover, but not Winterbor or Russian kales.
Choosing cold-hardy crops

Hoophouses for winter crops
• Rate of growth of cold-weather crops is much faster inside
• Crop quality, especially leafy greens, is superb.
• Plants can tolerate lower temperatures than outdoors; they
have the pleasant daytime conditions in which to recover.
Salad greens in a hoophouse can survive nights with
outdoor lows of 14°F (–10°C) without rowcover.
Photo Wren Vile
For details, see my
slide show
Hoophouse in Fall
and Winter
on SlideShare.net

Favorite winter-harvest crops – kale
and spinach
We grow about 2800 row feet of
overwinter Vates kale for 100 people
and plant another 1000 feet in spring.
We grow similar amounts of Tyee spinach.
We use double hoops and rowcovers and
pick spinach throughout the winter,
whenever leaves are big enough. We pick
one bed each day in October, November,
February and March, when the weather
is not too awful. Spinach makes some growth whenever the
temperature is above about 40°F (5°C), so we
can also make occasional harvests in
December and January.
Vates kale Credit Kathryn Simmons

More winter-harvest crops
As well as kale and spinach,
collards, leeks and parsnips also
survive outdoors without
rowcover at our farm (Zone 7).
We harvest small amounts of
collards throughout the winter,
and when spring arrives, the
plants give us big harvests
sooner than the new spring-
sown crops.
Leeks and parsnips are slow
growing, start them in spring.
Lettuce can be grown outdoors
with thick rowcover on hoops.
We have also sometimes
overwintered Danvers carrots
and Deadon cabbage.
Overwintered Vates kale

Winter-harvest leeks
Unlike onions, leeks grow
independently of day length
and will stand in the field at
temperatures below what many
other vegetables can handle,
increasing in size until you
harvest them.
Overwintered leeks.
Leek varieties – different types:
• Less hardy, faster-growing fall
varieties, often with lighter
green leaves, which are not
winter-hardy north of Zone 8,
Lincoln, King Richard.
• Giant Musselburgh (American
Flag) (105 days) is bolt-
resistant, for overwintering in
milder climates.
• Blue-green hardy winter leeks.
We like Tadorna (100 days),
Jaune du Poiteau, King Sieg,
Lorna, Bandit and Bleu de
Solaize (105 days, very hardy).

Other hardy winter-harvest crops
• Small greens such as arugula, parsley, Belle Isle upland cress, winter
purslane, salad burnet and mache (corn salad) are very winter-hardy.
• Some Asian greens are hardy. Best - Green in Snow mustard (Shi-Li-Hon)
• Some unusual crops like horseradish, Jerusalem artichokes, salsify, and
some endive are hardy.
• Walla Walla bulb onions and Evergreen Winter Hardy White or White Lisbon
scallions are surprisingly hardy.
• Swiss chard is hardy to 15°F (–10°C) without rowcover. To keep chard
overwinter, either use hoops and rowcover (in mild areas, Zone 6 or
warmer), or else cut off the leaves in early
winter and mulch heavily right over the
plants. It germinates best at 85°F (29°C) -
useful as a substitute if the fall is too hot to
sow spinach.
• Bright Lights chard. Credit Wren Vile

4. Overwinter early
spring-harvest crops
• spinach
• kale, collards, cabbage
• lettuce, chard
• carrots
• chicories such as radicchio
and Sugarloaf,
• scallions, potato onions
• garlic, garlic scallions.
• In mild areas, peas can be
fall sown for a spring crop.
Sow 1" (2.5 cm) apart to
allow for extra losses.
Planting garlic. Credit Brittany Lewis
Some crops, if kept alive through the winter,
will start to grow again with the least hint of
spring weather and be harvestable earlier
than spring plantings.

Garlic Scallions
Small whole garlic plants. An attractive early crop.
• Save small cloves from planting your main crop
• Plant close together in furrows, dropping them
almost end to end, as they fall. Close the furrow and
mulch over the top with spoiled hay or straw.
• Plant next to your main garlic patch, or in a part of
the garden that's easily accessible in spring.
• We harvest garlic scallions from early March till May,
at about 7-8" (18-20 cm) tall,
• Trim the roots, rinse, bundle, set in a small bucket
with a little water, and you're done!
• Scallions can be sold in small bunches of 3-6.
• Some people cut the greens at 10" (25 cm) tall, and
bunch them, allowing cuts to be made every two or
three weeks. We tried this, but prefer to simply pull
the whole plant. The leaves keep in better condition
if still attached to the clove. Photo Kathryn Simmons

Scheduling lettuce in fall
The short version on when to
sow:
• every 6-7 days in June and
July,
• every 5 days in early August,
• every 3 days in late August,
• every other day until Sept 21.
• every 3 days until the end of
September (for harvests
through the winter).
Tango cold-hardy lettuce
 Lettuce likes 40°F–80°F (4°C–27°C).
 Optimum 75°F (24°C) (germinates
in only 2 days).
 Max germination temperature is
85°F (29°C).
 Sow late afternoon or at nightfall -
better emergence than morning
sowings.

Scheduling fall broccoli and cabbage
 We start sowing our fall brassicas for
outdoor planting around June 26 and
repeat a week later for insurance -July
3
 Last date for sowing these crops is
about 3 months before the first fall
frost date. In our case that means July
14–20.
 We use nursery seedbeds - Our rough
formula is to sow around a foot (30 cm)
of seed row for every 12'–15' (3.6–4.6
m) of transplanted crop row.
 Harvest
– Cabbage from Sept 25 till late
November.
– Broccoli Sept 10–Oct 15, with
smaller amounts either side of
those dates.
Broccoli transplant.

Kale: direct sown/transplanted mix
Our mixed direct-sow/transplant
method allows for patchy
germination, and requires less
watering than if direct sowing it all.
Three times, (8/4, 8/10, 8/16), we
sow two beds with rows 10" (25 cm)
apart and then carefully thin them,
leaving one plant every foot (30 cm)
We use the carefully dug thinnings
from those beds to fill gaps and to
plant other beds, at the same plant
spacing.
Another reason we use this system is
that we want a lot of kale, and there
isn’t time to transplant it all.
Vates kale. Credit Kathryn Simmons

Scheduling Asian greens
The most cold hardy Asian greens can be
harvested all winter in milder climates or
kept alive until they revive in the spring to
provide early harvests.
Rowcovers on hoops will help keep them
in marketable condition, with faster
growth.
Wild Garden Seeds and Even’ Star Farm
specialize in very cold-tolerant varieties.
Hoophouses are the place to be in winter,
if you are an Asian green. With the
nighttime protection of two layers of
plastic and an air gap, September sowings
of these crops can thrive on the sunny
days and grow at a surprisingly fast rate.
We start sowing our
fall Asian greens for
outdoor planting the
same dates we sow fall
broccoli and cabbage-
the last date is 3
months before the first
fall frost date. In our
case that means July
14–20.
Michihili cabbage. Credit Southern
Exposure Seed Exchange

Scheduling hardy winter-harvest crops
• Slower-growing winter
hardy crops like leeks and
parsnips need sowing in
late spring. We sow in
March and April.
• Sow late cabbages
(Deadon, Brunswick and
January King ) in early
summer. (Early June for
us.)
Hollow Crown parsnips.

Scheduling spinach
• Eight weeks before the first fall frost date is a good time
to start planting spinach again, if it’s not too hot.
• Optimum germination temperature for spinach is 70°F
(21°C) Max 85°F (29°C). Wait for soil temperature to
drop (dead nettle, chickweed, henbit germinating).
• For earlier planting, pre-sprout seeds one week. We
sow sprouted spinach 9/1 or so.
Tyee spinach, our
favorite variety.

Scheduling overwinter crops for early
spring harvest
We sow one or two beds of spinach 9/20-9/30, overwinter them as
adolescents and harvest in the early spring. Spinach grows every time
air temperature tops 39°F (4°C).
They bolt later than the ones we harvest leaves from all winter, and
earlier than spring-sown beds, so we get a continuous supply.
Spinach, lettuce, chicories such as radicchio and Sugarloaf, fennel and
cilantro seem to have the best cold tolerance when the plants go into
winter half-grown.
With alliums, such as bulb onions, multiplier onions and garlic, the
harvest dates are regulated by day length, so the harvest cannot be
earlier, but the bulbs will be bigger if you can overwinter
the small plants.

When to plant garlic
• Fall-planting is best. Garlic emerges quickly in the fall
• 9 am soil temperature 50°F (10°C) at 4” (10 cm) deep. We plant
in early November. If the fall is unusually warm, wait a week.
• Roots grow whenever the ground is not frozen
• Tops grow whenever the temperature is above 40°F (4.5°C).

Winter hoophouse crop overview
• Salad crops
• cooking greens
• turnips
• radishes
• scallions
• bare root transplants for setting
outdoors in February and March
• We aim to harvest greens in the
hoophouse after the outdoor
crops slow down, and turnips
after the stored outdoor fall
turnips have all been eaten, or
as an occasional delectable
alternative.

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: Red and White Russian kales, another ten
varieties of lettuce, Senposai, more Yukina Savoy, mizuna
and arugula.
• We use hoops and ProtekNet, and water frequently.
Senposai. Credit Kathryn Simmons

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.
 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 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.
Late October we sow more
“filler” greens, baby lettuce
mix, spinach, turnips, chard,
and 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.

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 in early March.
 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

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.
• 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, hoeing,
hand weeding as needed.
• In the middle of winter, not much water is needed, and we try to only water when a
relatively mild night is forecast.

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.

Winter Hoophouse Harvest Dates
• October: radishes, tatsoi, spinach, beet greens
• From November onwards: spinach, lettuce leaves, chard,
mizuna, arugula, beet greens, tatsoi, brassica salad mix,
radishes and scallions.
• From December: baby lettuce mix, chard, kale, turnips;
• In December: heads of Tokyo Bekana, Maruba Santoh.
• January onwards: Senposai and Yukina Savoy.
• In January: heads of pak choy, Chinese cabbage, lettuce
• Most loose-leaf crops last until mid-March or later.
• 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

DIY weather-forecasting
Learn your local weather patterns by keeping records and watching
what happens.
• Our mid-Atlantic climate is controlled by three weather systems,
mainly by
– moisture from the Gulf of Mexico,
– the Bermuda High Pressure area in summer,
– the recurrent waves of cold Canadian air in winter.
• Rain (fairly evenly distributed throughout the year in our county)
– has slight peaks in January, February and March
– and again in early June and August.
• Some parts of our area can experience long periods of drought.
– September-November is the drier season but it’s also the hurricane
season, so the net result is very variable.
• We use Wunderground, but subtract 5F° from their forecast night
lows for our nearest town, and mentally downgrade the chance of
rain by 10%, as rain often passes us by as it scoots along the river
valley north of us.

Storage of Vegetables in Winter
Winter Squash storage
• Meeting the different storage
requirements of various crops helps
maximize their season of availability
• Many crops may be stored without
electricity, perhaps in buildings that
serve other uses at the height of the
growing season.
• A publication from Washington State
University Extension, Storing Vegetables
and Fruits at Home, is a good
introduction to alternatives to
refrigerated storage, using pits, clamps
and root cellars. There is also good
information in USDA Agriculture
Handbook 66.
• Some vegetables need to cure before
storage and the curing conditions are
different from those needed for storage.
Curing allows skins to harden and some
of the starches to convert to sugars.

Four Sets of Storage Conditions
In my chart on the next slide, the Summary column indicates the
general conditions needed for each crop, and allocates each crop to
one of 4 groups:
A= Cold and Moist : 32°F–40°F (0°C–5°C), 80%–95% humidity —
refrigerator or winter root cellar conditions. Most roots, greens, leeks
B= Cool and Fairly Moist: 40°F–50°F (5°C–10°C), 85%–90% humidity —
root cellar. Potatoes
C= Cool and Dry: 32°F–50°F (0°C–10°C), 60%–70% humidity — cooler
basements and barns. Garlic and onions
D= Warm and Dry to Fairly Moist: 50°F–60°F (10°C–15°C), 60%–70%
humidity — basements. Sweet potatoes and winter squash.
By providing storage spaces with these 4 types of conditions, 25 crops
can be stored.

Table of
Storage
Conditions
See the
handout or
my book
Sustainable
Market
Farming, for
the
complete
chart

In-ground storage
 Depending on the severity of your winter temperatures, some cold-hardy
root crops (such as turnips, rutabagas, carrots, parsnips, Jerusalem
artichokes and horseradish) and also leeks can be left in place in the
ground, with about a foot (30 cm) of insulation (such as straw, dry leaves,
chopped corn stalks, or wood shavings) added after the soil temperature
drops to “refrigerator temperatures.”
 Hooped rowcovers or polyethylene low tunnels can keep the worst of the
weather off. There could be some losses to rodents, so experiment on a
small scale the first winter to see what works for you. We have too many
voles to do this with carrots or turnips on our farm, but horseradish
survives without protection, as do some winter-hardy leek varieties.
 Besides being used as a method for storage of hardy crops deep into
winter, this can be a useful method of season extension into early winter
for less hardy crops such as beets, celery and cabbage, which would not
survive all-winter storage this way. Access to crops stored in the ground is
limited in colder regions — plan to remove them all before the soil
becomes frozen, or else wait for a thaw.
Drawing credit WSU Storing Vegetables and Fruits at Home

Storage clamps (mounds)
Cabbage, kohlrabi, turnips, rutabagas, carrots, parsnips, horseradish, Jerusalem artichokes,
salsify and winter radishes (and any root vegetables that can survive cold temperatures) can
be stored with no electricity use at all, by making temporary insulated outdoor storage
mounds (clamps).
• Mark out a circular or oval pad of soil, lay down some straw or other insulation, pile the
roots up in a rounded cone or ridge shape, and cover them with straw and then with soil,
making a drainage ditch round the pile. As a chimney for ventilation, leave a tuft of straw
poking out the center. Slap the soil in place to protect the straw and shed rainwater.
• For the backyarder, various roots can be mixed, or sections of the clamp can be for
different crops. Those growing on a large scale would probably want a separate clamp for
each crop. It is possible to open one end of a clamp or pit, remove some vegetables, then
reseal it, although it takes some care for it to be successful.
• There is a balance to be found between the thermal buffering of one large clamp and the
reduced risk of rot that numerous smaller clamps provide.

Pits and trenches
• To store in pits or trenches dig a hole in the ground first, lining it
with straw, lay in the vegetables, then cover with more straw and
soil. To deter rodents, it is possible to bury large bins such as (clean)
metal trash cans, layer the vegetables inside with straw, and cover
the lid with a mound of more insulation and soil. Trenches can have
sidewalls made with boards to extend the height.
• Another alternative is to bury insulated boxes in the ground inside a
dirt-floored shed or breezeway. A new life for discarded chest
freezers! Insulated boxes stored in unheated areas need six to eight
inches (15–20 cm) of insulation on the bottom, sides and top.

Root Cellars
• With a good in-ground root cellar, potatoes can be
stored for five to eight months.
• Potatoes are best stored in a moist, completely dark
cellar, at 40°F (5°C) to 50°F (10°C). Ventilate as
needed during times of cool temperatures, to keep
the cellar in the ideal range.
• Also for apples, cabbage, or root vegetables, but be
careful what you mix, because ethylene from the
apples, for example, will cause potatoes to sprout!
• Some people pack unwashed vegetables in boxes of
sand, wood ash, sawdust or wood chips. Perforated
plastic bags are a modern alternative.
• Whole pepper plants can be hung upside down in
the cellar to ripen, or simply to store.
• Headed greens like cabbage can also be hung upside
down, or be replanted side by side in tubs of soil.
• Celery and leeks can also be stored in the same way.
• See Nancy and Mike Bubel’s book Root Cellaring
Twin Oaks root cellar. Photo
McCune Porter

Ethylene
• Ethylene is associated with ripening, sprouting and rotting.
• Some crops produce ethylene in storage — apples, cantaloupes, ripening tomatoes
all produce higher than average amounts.
• Chilling, wounding and pathogen attack can all induce ethylene formation in
damaged crops.
• Some crops, including most cut greens, are not sensitive to ethylene and can be
stored in the same space as ethylene-producing crops.
• Other crops are very sensitive and will deteriorate in a high-ethylene environment.
Potatoes will sprout, ripe fruits will go over the top, carrots lose their sweetness
and become bitter. Drawing credit WSU Storing Vegetables and Fruits at Home

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.
 SARE www.sare.org A searchable database of research findings:
Season Extension Topic Room
 Washington State University Extension, Storing Vegetables and Fruits at
Home pubs.wsu.edu/ListItems.aspx?Keyword=EB1326E
 USDA Agriculture Handbook 66 ba.ars.usda.gov/hb66/contents.html
 extension.org/organic_production The organic agriculture community with
eXtension. Publications, webinars, videos, trainings and support.
 Growing Small Farms: growingsmallfarms.ces.ncsu.edu/ Debbie Roos keeps
this site up to the minute. Click Farmer Resources
 Wild Garden Seeds www.wildgardenseed.com
 Even ‘Star Farm http://www.localharvest.org/even-star-organic-farm-
M9994 specialize in cold-tolerant varieties.

Resources - slideshows
Many of my presentations are available at www.Slideshare.net. Search for Pam Dawling.
 Cold-hardy Winter Vegetables
 Crop Planning for Sustainable Vegetable Production
 Crop Rotations
 Fall Vegetable Production
 Feed the Soil
 Growing Great Garlic
 Hoophouses in Fall and Winter
 Hoophouses in Spring and Summer
 Intensive Vegetable Production on a Small Scale
 Producing Asian Greens
 Succession Planting for Continuous Vegetable Harvests
 Sustainable Farming Practices
 Year Round Vegetable Production
 Other slide shows I recommend:
 Mark Cain Planning for Your CSA: www.Slideshare.net (search for Crop Planning)
 Brad Bergefurd, Cultural Practices And Cultivar Selections for Commercial Vegetable
Growers. www.slideshare.net/guest6e1a8d60/vegetable-cultural-practices-and-variety-
selection

Resources - Books The Market Gardener, Jean-Martin Fortier, New Society Publishers
 The Complete Know and Grow Vegetables, J K A Bleasdale, P J Salter et al.
 Knott’s Handbook for Vegetable Growers, Maynard and Hochmuth
 The New Seed Starter’s Handbook, Nancy Bubel, Rodale Books
 Greenhouse and Hoophouse Grower's Handbook – Organic Vegetable Production Using Protected Culture,
Andrew Mefferd, New Society Publishers
 Sustainable Vegetable Production from Start-up to Market, Vern Grubinger,
http://host31.spidergraphics.com/nra/doc/fair%20use%20web%20pdfs/nraes-104_web.pdf NRAES
 The New Organic Grower and The Winter Harvest Handbook, Eliot Coleman, Chelsea Green
 Extending the Season: Six Strategies for Improving Cash Flow Year-Round on the Market Farm a free e-book for
online subscribers to Growing for Market
 Gardening When it Counts, Steve Solomon, New Society Publishers
 The Lean Farm, How to Minimize Waste, Increase Efficiency, and Maximize Value and Profits with Less Work
and The Lean Farm Guide Ben Hartman
 The Urban Farmer, Curtis Stone, New Society Publishers
 High-Yield Vegetable Gardening, Colin McCrate and Brad Halm, Storey Publishers
 Market Farming Success: The Business of Growing and Selling Local Food, Lynn Byczynski
 The Organic Farmer’s Business Handbook, Richard Wiswall, Chelsea Green
 Crop Planning for Organic Vegetable Growers, Daniel Brisebois and Frédéric Thériault (www.cog.ca)
 Nature and Properties of Soils, fourteenth edition, Nyle Brady and Ray Weil
 Garden Insects of North America, Whitney Cranshaw
 SARE Crop Rotations on Organic Farms, A Planning Manual, Charles Mohler, Sue Ellen Johnson, editors
 John Jeavons How to Grow More Vegetables has charts: Pounds Consumed per Year by the Average Person in
the US & Average US Yield in Pounds per 100 Square Feet

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