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Cold hardy winter vegetables 2017 dawling


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How to grow and store crops which tolerate cold weather. How to protect crops from cold weather with rowcover, Quick Hoops, caterpillar tunnels and hoophouses (high tunnels). Dealing with Persephone days, nitrate accumulation in leafy greens, the effect of ethylene on stored vegetables
Winter-kill temperatures for vegetable crops,

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Cold hardy winter vegetables 2017 dawling

  1. 1. Cold-Hardy Winter Vegetables ©Pam Dawling 2017 Twin Oaks Community, Virginia Author of Sustainable Market Farming Published by New Society Publishers
  2. 2. 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.
  3. 3. 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
  4. 4. 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.
  5. 5. 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.
  6. 6. 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
  7. 7. 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
  8. 8. 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
  9. 9. 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.
  10. 10. 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.
  11. 11. 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.
  12. 12. 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.
  13. 13. 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.
  14. 14. 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).
  15. 15. 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.
  16. 16. 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
  17. 17. 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
  18. 18. 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. Credit Kathryn Simmons
  19. 19. 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
  20. 20. 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.
  21. 21. 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.
  22. 22. 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.
  23. 23. 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.
  24. 24. Yukina Savoy Outdoors in December After several nights at 16-17°F (-8 to -9°C)
  25. 25. 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
  26. 26. Senposai in November – the young hoophouse crop is almost ready to take over from the well-used outdoor crop.
  27. 27. 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
  28. 28. 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
  29. 29. 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
  30. 30. 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
  31. 31. 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
  32. 32. 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
  33. 33. 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).
  34. 34. 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
  35. 35. 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.
  36. 36. 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
  37. 37. 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.
  38. 38. 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. Credit Kathryn Simmons
  39. 39. 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
  40. 40. 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
  41. 41. 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
  42. 42. 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. Credit Kathryn Simmons
  43. 43. 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.
  44. 44. 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).
  45. 45. 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.
  46. 46. 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
  47. 47. 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
  48. 48. 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.
  49. 49. 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
  50. 50. 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.
  51. 51. 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.
  52. 52. 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
  53. 53. 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.
  54. 54. 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.
  55. 55. 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
  56. 56. 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
  57. 57. 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.
  58. 58. 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.
  59. 59. 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.
  60. 60. Table of Storage Conditions See the handout or my book Sustainable Market Farming, for the complete chart
  61. 61. 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
  62. 62. 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
  63. 63. 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
  64. 64. 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
  65. 65. 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
  66. 66. Resources – General ATTRA  Market Farming: A Start-up Guide,  Scheduling Vegetable Plantings for a Continuous Harvest,  Season Extension Techniques for Market Farmers.  SARE A searchable database of research findings: Season Extension Topic Room  Washington State University Extension, Storing Vegetables and Fruits at Home  USDA Agriculture Handbook 66  The organic agriculture community with eXtension. Publications, webinars, videos, trainings and support.  Growing Small Farms: Debbie Roos keeps this site up to the minute. Click Farmer Resources  Wild Garden Seeds  Even ‘Star Farm M9994 specialize in cold-tolerant varieties.
  67. 67. Resources - slideshows Many of my presentations are available at 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: (search for Crop Planning)  Brad Bergefurd, Cultural Practices And Cultivar Selections for Commercial Vegetable Growers. selection
  68. 68. 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, 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 (  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
  69. 69. Cold-Hardy Winter Vegetables ©Pam Dawling 2017 Twin Oaks Community, Virginia Author of Sustainable Market Farming Published by New Society Publishers