This document discusses growing cold-hardy winter vegetables. It provides tables listing the cold tolerance ranges of various crops and examples of suitable crops for different cold temperature ranges. The document recommends growing cool weather crops in fall to harvest before very cold weather, keeping crops alive outdoors as late into winter as possible, harvesting hardy winter crops, and overwintering early spring crops. Specific crop recommendations for winter growing include kale, spinach, lettuce varieties, Asian greens like tatsoi and Yukina Savoy, turnips, rutabagas, cabbage, collards, leeks, and parsnips. Rowcovers and hoop houses are also discussed for protecting crops from frost.

1. Cold-Hardy Winter Vegetables
©Pam Dawling 2014
Twin Oaks Community, Virginia
Author of Sustainable Market Farming
Published by New Society Publishers
SustainableMarketFarming.com
facebook.com/SustainableMarketFarming
pam@twinoaks.org

2. What’s in this presentation
• Why would you farm in winter?
• Tables of cold-hardiness
• Four ranges for cold-hardy crops
• Examples of suitable crops
• Scheduling outdoor crops
• Hoophouse growing in winter
• Storage
• Resources
• My contact info

3. Why grow winter vegetables?
People eat all year long!
Winter share CSAs are more in demand as the locavore
movement grows,
There is a year-round demand for local foods in stores and
markets.
Keep your customers,
Keep your crew,
Keep in shape!
It’s easier than the summer - you have fewer crops to take
care of,
Weeds grow slower in colder weather, planting dates may
become more flexible.

4. Before taking the plunge into winter
gardening
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.

5. Rowcover
 Wonderful rowcover : lightweight, easy to use, easy to
store. Edges need to be held down by bags of rocks or
sand, plastic jugs of water, or metal or wooden stakes
lying along the edges.
 To protect against frost, you need a heavyweight
rowcover. Thinner types are for protection from insects.
 Dupont Xavan 5131 (previously called Typar). 1.25
oz/sq yd) fabric, can last for more than six years.
Spunbonded polypropylene with UV stabilizers, 75%
light transmission, and provides about 6 degrees F
(3.3 degrees C) of frost protection.
 We also use Agribon 17 (or 19), spun-bonded
polypropylene 0.55 oz/sq yd, transmits 85% of
sunlight, and offers 4°F (2.2°C) of frost protection for
winter use.
 We think polypropylene rowcover lasts longer and is
tougher than polyester (Reemay).
 Thinner rowcover can be used doubled up in severely
cold weather, if you don’t have enough thick rowcover.
Photo credit Kathryn Simmons

6. Avoiding pitfalls of rowcover
 If you are growing on bare soil
rather than plastic mulch, weeds
will grow very well, secretly and out
of sight.
 Rowcover reduces light levels.
 Ventilate covered crops in mild
weather, so they don’t lose their
cold tolerance.
 Hoops keep rowcover from sticking
to frozen leaves and reduce
abrasion. 9- or 10-gauge wire. In
winter we use double wire hoops
— the outer hoops trap the
rowcover so it doesn’t blow away.
The microclimate under hooped
rowcovers is very pleasant in chilly,
windy weather.
 There are also spring steel hoops,
for setting by machine or by hand.
Easy to store - they return to a
relaxed bow shape when removed
from the soil, don’t get tangled.
Seem to come in just one length,
64" (1.63 m), which is fine for a
single row of plants, but less good
for our 48" (1.2 m) beds with
multiple rows.

7. Protection from pests
For nursery seedbeds we use
rowcover or ProtekNet (from Purple
Mountain Organics) on wire hoops.
Overly thick rowcover or rowcover
resting directly on the plants can
make the seedlings more likely to die
of fungal diseases in hot weather —
good airflow is vital.
For transplanted crops, an 84" (2.1 m)
width rowcover or mesh can form a
tunnel over two crop rows 34” apart,
giving good airflow.
Photo credit Dubois Engineering

8. Winter Hardiness Table –
Frosty Weather
Some starting numbers of killing temperatures, although your own
experience with your soils, microclimates and rain levels may lead you to
use different temperatures:
• 35°F (2°C): Basil.
• 32°F (0°C): Bush beans, cauliflower curds, corn, cowpeas, cucumbers,
eggplant, limas, melons, okra, some pak choy, peanuts, peppers, potato
vines, squash vines, sweet potato vines, tomatoes.
• 27°F (–3°C): Some cabbage, Sugarloaf chicory (takes only light frosts),
radicchio.
• 25°F (–4°C): Broccoli heads, chervil, chicory roots for chicons and hearts,
Chinese Napa cabbage, dill, endive (hardier than lettuce, Escarole more
frost-hardy than Frisée), annual fennel, 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), onion scallions.

9. Colder
• 22°F (–6°C): Arugula, tatsoi (both may survive colder than this).
• 20°F (–7°C): Some beets, cabbage heads (the insides may still be
good even if the outer leaves are damaged), celeriac, celtuce
(stem lettuce), perhaps fennel, some mustards/Asian greens
(Tendergreen, Tyfon Holland greens), radishes, turnips with
mulch 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, broccoli leaves, young cabbage, celery (Ventura)
with rowcover, cilantro, 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.

10. Colder still
• 12°F (–11°C): Some cabbage (January King, Savoy types), carrots
(Danvers, Oxheart), most collards, some fava beans (not the
tastiest ones), garlic tops if fairly large, most fall or summer
varieties of leeks (Lincoln, King Richard), large tops of potato
onions, Senposai, some turnips (Purple Top).
• 10°F (–12°C): Beets with rowcover, purple sprouting broccoli for
spring harvest, Brussels sprouts, chard (green chard is hardier
than multi-colored types), Deadon cabbage, some collards
(Morris Heading), Belle Isle upland cress, some endive (Perfect,
President), young stalks of bronze fennel, perhaps Komatsuna,
some leeks (American Flag), Asian winter radish with mulch for
protection (including daikon), rutabagas, (if mulched), large leaves
of savoyed spinach (more hardy than flat leafed varieties), tatsoi.

11. Coldest
• 5°F (–15°C): Garlic tops if still small, some kale (Winterbor,
Westland Winter, perhaps Blue Ridge), some leeks (Bulgarian
Giant, Laura, Tadorna), some bulb onions (Walla Walla),
potato onions and other multiplier onions, 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, garlic, horseradish, Jerusalem artichokes, 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), parsnips, salad burnet, salsify, some spinach
(Bloomsdale Savoy, Olympia, Tyee).

12. 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

13. 1. Cool weather spring/fall crops to
harvest before very cold weather
Some crops grow in
spring and again in
the fall –
Asian greens,
beets,
broccoli,
cabbage,
carrots,
chard,
collards,
kale,
kohlrabi,
lettuce,
peas,
radishes,
rutabagas,
scallions,
spinach,
turnips.
Bed of young Danvers carrots.
Credit Kathryn Simmons

14. 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. Celeriac
takes 20°F (–7°C )
Large Smooth Prague celeriac.
Credit Southern Exposure Seed Exchange.

15. 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

16. 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.

17. 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.

18. 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) across for cooking
green.
• Can transplant at 6" (15 cm)
• Kitazawa Seeds have a Red Violet
tatsoi, with an upright habit
• Takes 21 days to become baby
salads
• 45 days to reach cooking size
Yukina Savoy
• like a bigger tatsoi, with blistered
dark green leaves, greener stems
and delicious flavor
• about 12“ (30 cm) tall
• 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.

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

20. 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

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

22. 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.
Credit Southern Exposure Seed Exchange

23. 3. Hardy winter-harvest crops
Deadon cabbage
Credit Johnny’s Selected Seeds
Use the cold-hardiness table to
look 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 cultivars. At
our Zone 7 farm, we overwinter
Vates kale without rowcover, but
not Winterbor or Russian kales.
We grow our winter-harvest crops
in our raised bed area, which is
more accessible in winter and
more suited to small quantities.

24. Favorite hardy 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

25. More cold-hardy winter-harvest
crops
As well as kale and spinach, collards,
leeks and parsnips also survive
outdoors without rowcover at our
farm (Zone 7).
We grow only a few hundred feet of
collards. We harvest small amounts
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

26. 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 - two main types:
• the less hardy, faster-growing
varieties, often with lighter
green leaves, which are not
winter-hardy north of Zone 8,
• the blue-green hardier winter
leeks. We like Tadorna (100
days), Jaune du Poiteau, King
Sieg (84 days, a cross between
King Richard and the winter-
hardy Siegfried, from Fedco)
and Bleu de Solaize (105 days,
very hardy). Giant Musselburgh
(105 days) is bolt-resistant, for
overwintering in milder
climates.

27. 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

28. 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.

29. 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

30. 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
Credit Kathryn Simmons
 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.

31. 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
 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.
 Last date for sowing these crops is
about 3 months before the first fall frost
date. In our case that means July 14–20.
 Harvest
– Cabbage from Sept 25 till late
November.
– Broccoli Sept 10–Oct 15, with smaller
amounts either side of those dates.
Broccoli transplant. Credit Kathryn Simmons

32. 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

33. 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, and ameliorate the
microclimate, for better growth rate.
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 for
sowing is about three
months before the first
fall frost date. In our
case that means July
14–20.
Michihili cabbage. Credit Southern
Exposure Seed Exchange

34. 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.
Credit Southern Exposure Seed Exchange

35. Scheduling spinach
• Optimum germination temperature for spinach is 70°F (21°C) Max
85°F (29°C). Eight weeks before the first fall frost date is a good
time to start planting spinach again, if it’s not too hot. 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.
• 9/20-9/30 sowings over-winter small and make harvests in early
spring. It grows every time air temperature tops 39°F (4°C).
Tyee spinach, our favorite variety. Credit Kathryn Simmons

36. Scheduling overwinter crops for early
spring harvest
We sow one or two beds of spinach in late September, overwinter
them as adolescents and harvest in the spring. These plants 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.
Garlic scallions are a great early spring crop – easy,
flavorful, unusual.

37. 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).

38. The hoophouse in 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 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).
• Working in winter inside a hoophouse is much more pleasant
than dealing with frozen rowcovers and hoops outdoors.
• Greenhouses and coldframes also offer opportunities for
cold-weather cropping, but get a hoophouse if you can.

39. 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.

40. 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

41. 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

42. Fall Hoophouse Planting - October
 Oct 15 we sow our first turnips. (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).
 Our neighbor Gary Scott sows beet plugs
in mid Oct, transplants them in the
hoophouse and harvests from mid-
March. Ace in 72 plug trays. He also loves
a new variety from Johnny's called
"Babybeat.”
 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.
By mid-October we clear and
prepare another bed and transplant
lettuce at 10" (25 cm) apart, and
chard.

43. 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

44. 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, 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.

45. Persephone days and
scheduling winter
hoophouse crops
• When the daylight is shorter than 10 hours a day not much growth
happens. It depends 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.
• Be aware of the increase in days to maturity in winter.
• 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.

46. Nitrate accumulation
• During periods of short daylight length, there is a health risk
associated with nitrate accumulation in leafy greens. Nitrates are
converted in the body into toxic nitrites, which reduce the blood’s
capacity to carry oxygen. Also, nitrites can form carcinogenic
nitrosamines.
• 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.
• Spinach, mustard greens and collards contain about twice as much
as lettuce; radishes, kale and beets often have two and a half times
as much. Turnip greens are especially high, at 3 times lettuce levels.

47. To keep nitrate levels as low as possible:
 Grow varieties best suited for winter;
 Avoid fertilizing with blood meal or feather meal; 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;
 Use crops soon after harvest;
 Refrigerate immediately after harvest, store harvested greens at
temperatures close to freezing;
 Mix your salads; don’t just eat spinach.

48. Winter Vegetable Storage
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.

49. 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.

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

51. 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

52. 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.
Drawing credit WSU Storing Vegetables and Fruits at Home

53. 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.
Drawing credit WSU Storing Vegetables and Fruits at Home

54. Root Cellars
• A sustainable alternative to refrigerated storage for
crops needing cool, damp conditions. 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, ideally at 40°F (5°C), up to 50°F (10°C). Ventilate
as needed during times of cool temperatures, to
maintain the cellar in the ideal range.
• Below 40°F (5°C) the starches start to convert to sugars,
giving the potatoes an unpleasant flavor and causing
them to blacken if fried.
• 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!
Most other root crops can also be stored in a root
cellar. Some people pack the unwashed vegetables in
boxes of sand, wood ash, sawdust or wood chips.
Perforated plastic bags are a modern alternative.
Whole pepper plants with unripe peppers 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 boxes or tubs of
soil. Celery and leeks can also be stored by replanting in
the same way.
• See Nancy and Mike Bubel’s book Root Cellaring for
construction details and advice
Twin Oaks root cellar. Credit McCune Porter

55. Ethylene
Ethylene is generally associated with ripening, sprouting and rotting. Some
crops produce ethylene gas while in storage — apples, cantaloupes and
ripening tomatoes all produce higher than average amounts. Environmental
stresses such as chilling, wounding and pathogen attack can all induce
ethylene formation in damaged crops. Some crops, including most cut greens,
are not very sensitive to ethylene and so can be stored in the same space as
ethylene-producing crops. Other vegetables, however, are very sensitive to
the gas 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

56. 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
 Virginia Co-operative Extension Service Fall Planting Guide
pubs.ext.vt.edu/426/426-334/426-334.html
 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,

57. 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
 Intensive Vegetable Production on a Small Scale
 Producing Asian Greens
 Succession Planting for Continuous Vegetable Harvests
 Sustainable Farming Practices
 Other slide shows I recommend:
 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

58. Resources – books and seeds
 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
 The Organic Farmer’s Business Handbook, Richard Wiswall, Chelsea Green
 Sustainable Vegetable Production from Start-up to Market, Vern Grubinger,
 The New Organic Grower, 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 magazine
 Gardening When it Counts, Steve Solomon
 Grow a Sustainable Diet: Planning and Growing to Feed Ourselves and the Earth,
Cindy Conner, New Society Publishers
 Crop Planning for Organic Vegetable Growers, Daniel Brisebois and Frédéric
Thériault (Canadian Organic Growers www.cog.ca)
 Growing Great Garlic, Ron Engeland, 1991, Filaree
 Wild Garden Seeds www.wildgardenseed.com
 Even ‘Star Farm http://www.localharvest.org/even-star-organic-farm-
M9994 specialize in cold-tolerant varieties.

59. Cold-Hardy Winter Vegetables
©Pam Dawling 2014
Twin Oaks Community, Virginia
Author of Sustainable Market Farming
Published by New Society Publishers
SustainableMarketFarming.com
facebook.com/SustainableMarketFarming
pam@twinoaks.org