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Hoophouse in fall and winter Pam Dawling



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How to use the hoophouse in fall and winter to grow varied and plentiful greens for cooking and salads; turnips, radishes, scallions. How to get continuous harvests and maximize use of this valuable space. Tips to help minimize unhealthy levels of nitrates in cold weather. Growing bare-root transplants for planting outdoors in spring. Growing early warm-weather crops. Transplanting indoors from outdoors in the fall.

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Hoophouse in fall and winter Pam Dawling

  1. 1. The Hoophouse in Fall and Winter ©Pam Dawling 2015 Twin Oaks Community, Central Virginia Author of Sustainable Market Farming Published by New Society Publishers
  2. 2. What’s in this presentation 1. Overview of the hoophouse in fall and winter 2. Tables of cold-hardiness 3. Suitable crops for fall and winter 4. Scheduling 5. Tasks and challenges 1. Winter hoophouse tasks 2. Irrigation 3. Soil fertility, crop rotations 4. Cold weather pests 5. Persephone Days and Nitrate accumulation 6. Resources 7. My contact info
  3. 3. The hoophouse in fall and winter We are amazed at how incredibly productive hoophouses are. • Rate of growth of cold-weather crops is much faster inside • Crop quality, especially leafy greens, is superb. • Plants tolerate lower temperatures than outdoors; they recover in the pleasant daytime condition. Salad greens in a hoophouse can survive nights with outdoor lows of 14°F (–10°C). Add thick rowcover and they can survive an outdoor low of -12°F (-24°C) • Working in winter inside a hoophouse is much more pleasant than dealing with frozen rowcovers and hoops outdoors. • Get a hoophouse if you can. Get another!
  4. 4. Growing in the winter hoophouse  Night-time protection of two layers of plastic and an air gap – big difference!  Fall sowings thrive on sunny winter days.  When the daylight falls below ten hours, growth slows down till spring.  In colder climate zones and outdoors here, mature plants are mostly being stored for harvest.  For most of the winter, our zone 7 central Virginia hoophouse plants are actively growing, so we continue sowing new crops even in December. • Photo credit Wren Vile
  5. 5. Winter hoophouse crops • Salad crops • cooking greens • Asian greens • roots • onions • early peas, fava beans • bare root transplants for setting outdoors in February & March Our hoophouse keeps night time temperatures about 7F warmer than outdoors, sometimes 10F. Plus, plants tolerate lower temperatures – it seems to be the night+day average that counts.
  6. 6. Cold-hardiness table for hoophouse crops – Frosty weather Some starting numbers of outdoor killing temperatures, although your results may vary. In the hoophouse (7F warmer than outside), plants can survive 14F colder than outside without extra rowcover, 21F colder than outside with thick (1.25ozTypar/Xavan) rowcover. • 35°F (2°C): Basil. • 32°F (0°C): some pak choy, peppers, tomatoes. • 25°F (–4°C): Chinese Napa cabbage, endive (hardier than lettuce, Escarole more frost-hardy than Frisée), large leaves of lettuce (protected hearts and small plants will survive even colder temperatures), some mustards and Asian greens (Maruba Santoh, mizuna, most pak choy, Tokyo Bekana), some onion scallions. A test year: Lettuce and Mizuna survived a hoophouse temperature of 10.4°F without rowcover, -2.2°F with.
  7. 7. Colder • 22°F (–6°C): Some arugula, tatsoi (both have varieties which survive much colder than this). • 20°F (–7°C): Some beets, celtuce (stem lettuce), Tendergreen, Tyfon Holland greens, radishes, turnips with mulch or rowcover to protect them (Noir d’Hiver is the most cold- tolerant variety). • 15°F (–9.5°C): Some beets (Albina Verduna, Lutz Winterkeeper), beet leaves, endive, fava beans (Aquadulce Claudia), Russian kales, kohlrabi, Komatsuna, some lettuce, especially small and medium-sized plants (Marvel of Four Seasons, Rouge d’Hiver, Winter Density), parsley, Asian winter radish (including daikon), large leaves of broad leaf sorrel, turnip leaves, winter cress. A test year: Lettuce, Mizuna, Turnips, Russian kales survived a hoophouse temperature of 10.4°F without rowcover, -2.2°F with.
  8. 8. Colder still • 12°F (–11°C): Some carrots (Danvers, Oxheart), most collards, some fava beans, Senposai, some turnips (Purple Top). • 10°F (–12°C): chard (green chard is hardier than multi-colored types), Belle Isle upland cress, some endive (Perfect, President), perhaps Komatsuna, Asian winter radish (including daikon) with mulch or rowcover for protection, large leaves of savoyed spinach (more hardy than flat leafed varieties), most tatsoi, Yukina savoy. For a complete list of cold-hardy crops indoors and out, see my slideshow Cold-hardy Winter Vegetables on A test year: Lettuce, Mizuna, Turnips, Russian kales, Senposai, Tyee spinach, Tatsoi, Yukina Savoy survived a hoophouse temperature of 10.4°F without rowcover, -2.2°F with. Brite Lites chard got frozen leaf stems.
  9. 9. Coldest • 5°F (–15°C): Some kale (Winterbor, Westland Winter, perhaps Blue Ridge), some leeks (Bulgarian Giant, Laura, Tadorna), some bulb onions (Walla Walla), smaller leaves of savoyed spinach and broad leaf sorrel, a few unprotected lettuces if small (Winter Marvel, Tango, North Pole, Green Forest). • 0°F (–18°C): Chives, some collards (Blue Max, Winner), corn salad, Vates kale (although some leaves may be too damaged to use), Even’ Star Ice-Bred Smooth Leaf kale, a few leeks (Alaska, Durabel), some onion scallions (Evergreen Winter Hardy White, White Lisbon), salad burnet, salsify, some spinach (Bloomsdale Savoy, Olympia, Tyee). Remember these are outdoor temperatures. It’s warmer inside!
  10. 10. Which Crops are Most Profitable? Some crops offer more money per area, some are more profitable in terms of time put in. Clifton Slade at Virginia State University in his 43,560 Project (how to earn $43,560 from one acre), recommends choosing crops which produce one vegetable head or stalk, or 1 pound of produce, per square foot. Leafy crops feature prominently. -------------------------------------------------------------------------------- Richard Wiswall Organic Farmer’s Business Handbook Leafy greens, parsley and basil earned more than fruiting crops. Michihili cabbage. Credit Southern Exposure Seed Exchange
  11. 11. Which Crops Take Most Attention? Steve Solomon in Gardening When it Counts provides tables of vegetable crops by the level of care they require. His Difficult List includes bulb onions, leeks, Chinese cabbage, asparagus, celery, celeriac, cauliflower, Brussels sprouts, early cabbage and cantaloupe. Your results may vary! Onion bed. Photo Kathryn Simmons
  12. 12. Reasons to Grow Crops That Don’t Make the Highest Income  provide a good crop rotation for your farm,  provide diversity (customers will only buy so much parsley and basil).  provide for times of the year when fewer growers are selling produce: fall crops to harvest before serious cold, crops for all-winter harvests, early spring harvest markets with overwintering crops. Kohlrabi. Photo McCune Porter
  13. 13. Salad Crops • Lettuce heads may survive much colder temperatures than you ever imagined! • Baby lettuce mix is popular and easy • Many cooking greens can be used as salad crops while plants are small. • Several small greens are very winter-hardy.
  14. 14. Lettuce Heat-tolerant varieties also tolerate cold. There are also specialized cold-hardy varieties that do not tolerate heat (because they have a relatively low water content). Sow these in fall and winter only. Lettuce germinates at 40°F–85°F (4°C–29°C). Optimum 75°F (24°C) Sow late afternoon/evening - better emergence than mornings. Adolescent lettuce are more cold-hardy than full-sized plants.
  15. 15. Lettuce varieties for fall and winter Particularly cold-hardy:  Brune d’Hiver  Cocarde  Esmeralda  Galactic  Green Forest  Hyper Red Wave  Kalura  Lollo Rossa  North Pole  Red Tinged Winter  Rossimo  Rouge d’Hiver  Sunfire  Tango  Vulcan  Winter Marvel Rouge d’Hiver Lettuce Credit Southern Exposure Seed Exchange The Salad Bowls are not so good outdoors in cold weather but do well in the hoophouse. Icebergs do not survive frost.
  16. 16. Baby Lettuce Lettuce Mixes Small-leaf lettuces: Osborne’s Multileafs, Johnny’s Salanovas, Tango, Oscarde, Panisse. Photo credit Osborne Seeds Lettuce Mix. Credit Twin Oaks Community
  17. 17. Asian-type brassica salad mixes Wild Garden Pungent Mix, Brassica juncea, (Wild Garden Seeds, Fedco). A cross of pungent Indian mustards for those who like Big Flavor. 40 days to harvest. Photo credits Wild Garden Seeds Pink Petiole Mix, Brassica rapa (Wild Garden Seeds, Fedco). Fast-growing, cold tolerant, adds a touch of color to the brassica portion of winter salad mixes. A varied mix of colors and shapes. Ready in 40 days.
  18. 18. Mizuna/kyona • Ferny leaves - add color and loft in salad mixes • Mild flavor • Available in green or purple (but Ruby Streaks is much better then Purple Mizuna!) • Regrows vigorously after cutting • Use for baby salads after only 21 days • or thin to 8"–12" (20–30 cm) apart, to grow to maturity in 40 days • Very easy to grow, tolerates cold wet soil. • Fairly heat tolerant (well, warm tolerant) • Cold tolerant to 25°F (-4°C) Photo credit Ethan Hirsh
  19. 19. Ruby Streaks, Golden Frills, Scarlet Frills, Red Rain Johnny’s Red Splendor Ruby Streaks Credit Southern Exposure Seed Exchange Golden Frills
  20. 20. Other salad crops • Sylvetta, Surrey and Astro varieties of arugula are particularly cold-hardy. Even’Star arugula photo credit SouthernExposure Seed Exchange • Parsley, Belle Isle upland cress, winter purslane, salad burnet and mache (corn salad) are also very winter-hardy. Belle Isle Upland Cress. Photo Credit Southern Exposure Seed Exchange
  21. 21. Leafy cooking greens in the hoophouse Brassicas and spinach are the most productive crops in winter (more so than lettuce) Night-time protection of two layers of plastic and an air gap – big difference! Photo credit Twin Oaks Community
  22. 22. Hardy cooking greens • Spinach – we like Tyee and are trialing Abundant Bloomsdale • Russian kales (better than Vates in the hoophouse). Most Napus kales (Siberian and Russian) make faster growth during the low-light, colder months of winter, compared to Oleracea kales like Vates. Many Oleracea kales are more cold tolerant than napus sp., but they enter a dormant phase and then bolt in early spring. Thanks Clara Coleman • Swiss chard germinates best at 85°F (29°C) - useful as a substitute if the fall is too hot to sow spinach. Fordhook Giant, Artgentata, Leaf Beet are hardy varieties • Senposai • Other Asian greens • Bright Lights chard. Credit Wren Vile
  23. 23. Asian Greens • Grow particularly well in the hoophouse, all winter in zone 7. • Huge range of attractive varieties • Grow when you normally grow kale • Short spring season, bolt when it gets hot • Long fall season, no bolting. Blues Napa Chinese cabbage Credit Ethan Hirsh  Green in Snow mustard (Shi-Li-Hon) is reportedly the hardiest Asian green.  In spring the order of bolting of Asian greens is: tatsoi, pak choy, Komatsuna, mizuna, leaf radish, mustards.
  24. 24. Advantages of Asian greens  A quick way to fill out your market booth or CSA bags  A catch crop for spaces where other crops have failed or otherwise finished early. Keep a flat of seedlings ready, pop plugs into empty spaces as they occur.  Better able to germinate in hot weather than lettuce.  Faster growing than lettuce  Some of the faster-growing types are ready for transplanting 2 weeks after sowing (or you can direct sow them)  Trial many kinds, use unwanted seed in baby salad mix! Photo credit Ethan Hirsh
  25. 25. Healthful Diversity!  Flavors vary from mild to peppery - read catalog descriptions before growing lots  Colors cover the spectrum: chartreuse, bright green, dark green and purple.  Nutritious as well as tasty.  High in carotenoids, vitamins A and C, calcium, iron, magnesium and fiber.  Help prevent high blood pressure, heart disease and stroke.  Also contain antioxidants which fight against cancer and protect eyes from macular degeneration Photo Credit Ethan Hirsh
  26. 26. Senposai - Our star of Asian greens • Senposai is quite heat and cold tolerant, a big plant with large, round, mid-green leaves. • Transplant it at 12"–18" (30–45 cm) spacing. • Only 40 days to mature. • Usually harvested leaf-by-leaf. It can be very productive. • Cooks quickly (much quicker than collards), and has a delicious sweet cabbagey flavor and tender texture. • A cross between komatsuna and regular cabbage. Senposai. Photo Ethan Hirsh
  27. 27. Komatsuna • Also known as mustard spinach (as Pak Choy is too!) and Summer Fest • Green or red (purple) • Baby salad size in 21 days, full size in 35 days • Grows into a large plant 18" (45 cm) tall • Individual leaves can be picked and bunched • Or the whole plant can be harvested • The flavor is much milder than the English name suggests - mildly peppery • Cold-tolerant to 15°F (-9.5°C), perhaps 10°F (-12°C) Photo credit Fothergill Seeds Photo credit Fothergill Seeds
  28. 28. Napa and Michihili Wong Bok Chinese cabbage • Very tender, light green leaves • Excellent for stir-fries and pickling. • Hardy to about 25°F (–4°C) • The cylindrical Michihili produces 16" (40-cm) tall heads 6" (15 cm) across. Barrel-shaped Napa cabbage produce less in the same space. • Michihili is more stress tolerant and resistant to bolting and black speck than Napa cabbage. • Napa cabbage stores longer. • We like Blues Napa cabbage (52 days from seed to harvest) and Jade Pagoda (72 days) and the O-P Michihili (72 days) Photo credit Southern Exposure Seed Exchange
  29. 29. Celery cabbage, pe tsai: Tokyo bekana and Maruba Santoh Photo credit Johnnys Seeds • Fast-growing, looseleaf, non- heading vegetables with tender chartreuse (yellow-green) leaves and white petioles. Mild flavor • Can be harvested as baby leaves after 21 days • Or the leaves and wide white stems of the mature plant provide crunch for salads from 35 days after sowing. • Or whole plants can be chopped and lightly cooked • More heat tolerant than Napa. Cold tolerant to 25°F (-4°C). Fairly bolt resistant
  30. 30. Pak choy/bok choi • Sturdy white leaf stems, big green leaves. Usually harvested as a head 12"–15" (30–38 cm) tall • 45–55 days to maturity • Hardy down to 32°F (0°C), most varieties to 25°F (-4°C) • Can be picked as individual leaves, for bunches of mixed braising greens or stir-fry combinations • We grow Prize Choy or Joy Choi • There is also red choi (a 45-day, red-veined baby leaf or maroon- leaved full-size version) • Photo credit Johnnys Seeds
  31. 31. More big Asian greens  Tyfon Holland Greens - a strong hybrid of komatsuna with a heading brassica. Could be good in a survival situation, or to grow for goats. Hardy down to 20°F (-7°C).  Tenderleaf – a big, sturdy, OP plant. Quick-cooking, mild- flavored, despite appearances. Very disease-resistant . Cold tolerant down to 20°F (-7°C). Can be sown later in the fall than other greens - could be the solution if your original plan didn’t work. Can be a useful salad mix crop at the baby stage. Mizspoona, Brassica rapa, a large sturdy plant, 40 days to maturity. A sweet flavor with a good balance of mild zinginess. A gene pool (variable plants). Mizuna crossed with Tatsoi. Credit Wild Garden Seeds
  32. 32. Other big greens • Chinese Thick-Stem Mustard (SESE, Fedco, Even' Star Organic Farm, Maryland). Multiple cuttings of balanced- flavor salad mix crop to fill the CSA bags. Extremely cold tolerant. • Toraziroh, Brassica oleracea algoblabria, a robust producer of high yields of large leaves with a good, not overpowering flavor. Related to Chinese kale or Chinese broccoli. Relatively slow to bolt, ready in 45 days
  33. 33. • Transplants of Red Giant Mustard Photo credit Southern Exposure Seed Exchange • Mature Red Giant Mustard Photo credit Planet Natural Mustard greens Asian mustards such as Red Giant, Osaka Purple, and American Mustards (eg Southern Green Wave) are hardy to light frosts. Attractive colors. 21 days to baby leaves, 40–45 days full size
  34. 34. Tat soi/tah tsoi • A small flat rosette of shiny, dark green spoon-shaped leaves, green-white stems • 21 days for baby salads; 45 days for cooking • Mild flavor, an attractive appearance • Very cold tolerant, hardy to 10°F (–12°C) • Direct sow and then thin into salad mixes, leaving some to mature at 10" (25 cm) across for cooking greens. • Can transplant at 6" (15 cm) Photo credit Ethan Hirsh
  35. 35. Yukina Savoy • like a bigger tatsoi, • blistered dark green leaves and stems • delicious flavor • about 12“ (30 cm) tall • Tolerant to heat and cold – down to 10°F (-12°C) • Transplant at 12" (30 cm) • 21 days to reach baby size, 45 days to full size
  36. 36. Small and/or short-lived crops  Hon Tsai Tai (like a purple broccoli raab). Also known as Choy Sum. Mostly stem with small clusters of buds. In climates cooler than Zone 7 this might be productive in the fall. For spring it could be a challenge most places. It matures in only 35–40 days. Hardy to 23°F (–5°C). Photo credit Johnnys Seeds  Broccoli Raab We had the same trouble with this as with Hon Tsai Tai  Mei Qing Choi. A miniature 6" (15 cm) pak choy. These might suit your market, but we do better with larger vegetables. It matures in less than 45 days, a definite plus  Vitamin Green/Bitamin-Na/Yokatta-Na A slender, white- stemmed plant, about 12" (30 cm) tall. It can be planted 4" (10 cm) apart, or direct sown and thinned. Tolerates heat and cold. Quick-growing with good flavor, not pungent: 21 days for salad mix, 45 to its full size
  37. 37. Roots: Turnips Turnips do very well in the winter hoophouse. We sow our first ones Oct 15 (around our first frost date) for harvest from Dec 4. We like Red Round and Hakurei and have tried out Oasis and White Egg to find a cheaper replacement for Hakurei (Oasis is the closest). We do a second sowing Nov 9 and a small third sowing Dec 10. Scarlet Ohno Revival turnip White Egg turnip. Credit Southern Exposure Seed Exchange
  38. 38. Carrots • Carrots prefer soil temperatures of 45°F–85°F (7°C–29°C), • They germinate in 6 days at 80°F (27°C), their optimum. • Keep the soil surface damp until they come through. • Varieties suitable for winter hoophouses include Napoli, Nelson, Mokum and Rainbow Mix Photo credit Southern Exposure Seed Exchange
  39. 39. Beets • Beets prefer soil temperatures of 50°F–85°F (10°C–29°C) • Only 3.5 days to emerge at 86°F (30°C), but 14.6 days at 50°F (10°C). • Hand-sowing pre-sprouted seed is an option if the soil is too hot when you need to make fall sowings. • Sow 1/2″-1″ deep, tamp the soil, and keep the surface damp with daily watering until they emerge. • Varieties suitable for winter hoophouse use include Bulls Blood (for beautiful leaves), Babybeat (small, perfectly formed round beets). Crosby Egyptian Beet. Credit Southern Exposure Seed Exchange
  40. 40. Radishes Easter Egg radishes. Photo credit Southern Exposure Seed Exchange • Varieties that work well for us: Easter Egg (multicolored), White Icicle, and Cherry Belle • Sparkler got too fibrous for us, as did Cherry Belle after mid October • We make 6 sowings of radish between 9/6 and 1/26
  41. 41. Onions Scallions • We sow 9/6 for harvest 12/1 - 3/1 and 11/18 (following radishes) for harvest in early spring Photo credit Southern Exposure Seed Exchange Bulbing onions • We sow for growing to maturity in the hoophouse • We also grow seedlings for planting outdoors. Onion photo credit Kathryn Simmons
  42. 42. Peas and beans Fava beans sown 11/15 and harvested mid-May. Photo credit Kathryn Simmons Dwarf snap peas (sown 2/1) Photo credit Kathryn Simmons
  43. 43. Bare-root transplants • Plants dug up from a nursery seedbed and transplanted elsewhere. • Save time and money, compared to growing starts in flats. • Save on greenhouse space. • Very sturdy plants - full depth of soil to develop big roots • Little extra care needed - less prone to drying out than seedlings in flats. Photo credit Ethan Hirsh In October we sow “filler” greens and lettuce to use in the hoophouse during the winter In November we sow bulbing onions to plant outdoors 3/1 Jan 24 we sow kale, collards, spinach to plant outdoors in Mar.
  44. 44. Making a co-ordinated schedule  Make a map of the bed layout and plan the area each crop will occupy.  Decide on planting dates  Calculate harvest dates, and plan follow-on crops where possible.  Draw up a planting schedule in date order
  45. 45. Days to Maturity  ‘Days to maturity’ in catalogs are generally for spring planting once conditions have warmed to the usual range for that crop. When growing late into the fall, add about 14 days for the slowdown in growth.  It usually means ‘Days to First Harvest’ which may not be the same as ‘Days to Full Harvest’.  With carrots it exact size doesn’t matter, but an unheaded Chinese cabbage is no good.  With CSAs, you can distribute Pak Choy to some sharers one week, and others the next.  If it’s important to have a plentiful harvest when you do start, add another 7-14 days. Carrot photo Kathryn Simmons
  46. 46. Scheduling spinach and chard • Spinach is a challenging crop to start in hot weather! • Optimum germination temperature 70°F (21°C) Max 85°F (29°C). Wait for soil temperature to drop. • For earlier planting, pre-sprout seeds one week. We sow sprouted spinach 9/6 or so in our hoophouse. • Swiss chard germinates best at 85°F (29°C), so consider that as a substitute for a first sowing if the fall is impossibly hot. Tyee spinach. Credit Kathryn Simmons
  47. 47. Scheduling Beets • Sow beets dry or soaked for 1-2 hours in a little water. (Don’t soak too long, or in a lot of water – beet seeds are easy to drown.) We usually sow pre-soaked by hand. Sometimes dry with the EarthWay chard plate 2 passes. • We sow Bulls Blood beets 9/7 to use the tops in salad mixes • For early spring eating, sow Ace in 72 plug trays in mid Oct, transplant them in the hoophouse and harvest from mid-March. We are trying a new variety from Johnny's called Babybeat, seeded in February, for harvesting late April. • We sow Cylindra beets 2/15 for a late spring crop Photo Detroit Dark Red Beet. Credit Southern Exposure Seed Exchange
  48. 48. Fall Hoophouse Planting - September  Early September : We clear and add compost to one of the beds and sow sprouted spinach seed, radishes, scallions, Bulls Blood beet greens and tatsoi.  Sept 15 and Sept 24: We make outdoor sowings of crops to later transplant into the hoophouse at 2–4 weeks old. See next slide.  At the end of September we clear summer crops from one more bed, add compost and work it in. We transplant Tokyo Bekana and Maruba Santoh at 2 weeks old, Chinese cabbage, pak choy and Yukina Savoy at 3 weeks. Photo November hoophouse beds. Ethan Hirsh
  49. 49. Fall outdoor sowings to transplant inside • Sept 15: about ten varieties of hardy leaf lettuce and romaines, pak choy, Chinese cabbage, Yukina Savoy, Tokyo Bekana, Maruba Santoh, chard. • Sept 24: another ten varieties of lettuce, Red and White Russian kales, Senposai, more Yukina Savoy, mizuna and arugula. • We use hoops and ProtekNet, and water frequently. Senposai. Credit Kathryn Simmons
  50. 50. Fall Hoophouse Planting - October  By mid-October we clear and prepare another bed and transplant lettuce at 10" (25 cm) apart, and chard.  Oct 15 we sow our first turnips.  Sow Ace beets in 72 plug trays in mid Oct, transplant them and harvest from mid-March.  Late October we sow more “filler” greens, baby lettuce mix, our second spinach, turnips and chard, and more radishes.  In the fourth week of October, we clear and prepare more beds and transplant the Senposai, mizuna, the 2nd lettuce, kale, arugula and Yukina Savoy at 4 weeks old. Mizuna Photo credit Ethan Hirsh Early October, we sow more radishes and some “filler” greens, (spinach, lettuce and Asian greens) to fill gaps later. We try hard to keep all the space occupied, mostly using lettuce and spinach.
  51. 51. 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
  52. 52. Gather sowing and harvest start dates and draw graphs  Using your data, plot a graph for each crop, with sowing date along the horizontal (x) axis and harvest start date along the vertical (y) axis.  Mark the first possible sowing date and find the harvest start date for that.  Decide the last worthwhile harvest start date, mark that.  Then divide the period into a whole number of segments, according to how often you want a new patch. Cherry Belle radishes. Credit Southern Exposure Seed Exchange
  53. 53. Winter hoophouse radish succession cropping graph A work-in-progress! See my slide show on Succession Planting for Continuous Vegetable Harvests on
  54. 54. Daily hoophouse tasks in winter • Two hours work each day in winter in our 96’ x 30’ tunnel. • Keep the temperature in the 65°F–80°F (18°C–27°C) range during the day, opening the big high windows, and the doors as needed. If the sun is shining we usually open the windows around 9 am and close them around 2:30 pm (a few hours before dark) to store some of the warmth. Windows open above 40°F, doors above 50°F outside. • Even in cold weather, plants need fresh air! High-density cropping can really use up the carbon dioxide in a closed hoophouse very quickly. When this happens, photosynthesis crashes and plant growth becomes limited. Soil high in organic matter contains high levels of organisms that produce carbon dioxide. Dense plant canopies can trap this near soil level, where it is most useful. • Our main task each day is harvesting. In the winter of 2009–2010, we had frozen soil or snow on the ground outside for a month (very unusual for us). Despite this we were able to keep a hundred people in fresh salad and cooking greens (with turnips and scallions for variety) for the whole month. • Aside from harvesting, jobs include planting new crops, clearing old ones, spreading compost, hoeing, hand weeding and supplying water as needed. • We have drip irrigation. In the middle of winter, not much water is needed, and we try to only water when a relatively mild night is forecast.
  55. 55. Winter hoophouse harvest dates • November onwards: spinach, lettuce leaves, mizuna, arugula, beet greens, tatsoi and brassica mix for salad, radishes and scallions. • From December: baby lettuce mix, Tokyo Bekana, Maruba Santoh, chard, kale and turnips. Kale grows whenever it is above 40°F (5°C). • January till mid-March; the bigger greens, including Senposai, pak choy, Chinese cabbage and Yukina Savoy, lettuce heads. • Yukina savoy. Credit Ethan Hirsh
  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. Harvesting  Some crops are harvested as whole heads; others can be harvested by the leaf and bunched or bagged.  The open rosette types, such as tatsoi or the bigger Yukina Savoy, are usually gathered closed and banded with plant ties or rubber bands.  Most Asian greens can be grown for baby salad mix.  With mizuna we do a “half buzz- cut,” snipping off leaves on one half of the plant an inch (25 mm) above the ground each time we come by. Tat soi shown here. Credit Ethan Hirsh
  58. 58. Growing winter crops may involve sowing when soils are hot 1. Consult the tables in Nancy Bubel’s New Seed Starter’s Handbook or Knott’s Vegetable Grower’s Handbook, on the germination requirements for your crop, and the expected time to emergence under your field conditions – and use a soil thermometer. 2. If soil temperatures are too high for good germination, cool a small part of the outdoors: – Shade from other plants, shadecloth, boards, burlap bags, – For crops you normally direct seed, consider cooling a small nursery bed for your seedlings and transplanting later. 3. If outdoors is impossible, start seeds indoors: – Put a plastic flat of lettuce in your refrigerator or a cool room. – Use plug flats or soil blocks rather than open flats, to reduce transplant shock.
  59. 59. Irrigation  Need plenty of water to grow pleasant-tasting leaves.  1” (2.5 cm) of water per week is often enough  During very hot weather, 2” (5 cm) is better  Drip irrigation saves water and reduces disease and weed pressure.  In summer, the faster growing types of Asian greens are ready to plant out 2 weeks after sowing. Napa cabbage, Tokyo Bekana and Maruba Santoh are in this category.  Most others transplant best at 3–4 weeks of age (less time than needed in spring).
  60. 60. Water is Vital for Transplants! Damp soil is important before, during and after transplanting. Water your plants an hour before transplanting, and then also well after planting. If necessary, in very dry weather, water the soil ahead of planting. Use drip tape with emitters at the chosen crop spacing, water for twenty minutes before planting, and then plant directly into the wet spots. No other measuring is needed. Water the transplants the next day, on days three, seven and ten after planting, and then weekly after that. Senposai. Photo credit Ethan Hirsh
  61. 61. Compost is Central to our Soil Fertility Program • One of our community businesses is making and selling tofu. Okara is a high-nitrogen waste product from tofu making, the part of the soybeans that doesn’t go into the soymilk. • We mix in high-carbon sources such as sawdust (waste from our hammock-making business) or woodchips that we trade for with a neighbor. • We also add kitchen scraps from our dining hall, • and sometimes weeds or crop refuse from our garden. In the summer we don’t collect up the weeds, just let them die in place, as that is easier. • We don’t have specialized compost-turning machines or screens. We use the tractor bucket to lift and turn the piles.
  62. 62. Finished Compost Finished compost ideally has a C:N (carbon:nitrogen) ratio of 10:1. If the C:N ratio is greater than about 25:1, almost no nitrogen is available from the compost and it is unable to mineralize. Between 16 and 20:1, about 10 percent of the N is available. Even at a C:N ratio of 10:1, only half of the nitrogen is available in the near term.
  63. 63. How Much Compost?  In his Winter Harvest Handbook, Eliot Coleman recommends 5 gallons/ 25 ft2 or 15 tons/acre (8.6 l/m2) of raised beds, for each successive crop.  Compost improves the soil structure, organic matter and humus.  Effects last longer than cover crops and crop residues, especially in humid conditions where the breakdown of plant material is very rapid.  Compost can add a range of beneficial bacteria and fungi, which can inoculate plants against diseases by inducing systemic acquired resistance. The plants produce antibodies and other protective compounds before any infection can occur.
  64. 64. Crop Rotations • We work out an ad-hoc plan for each year, juggling rotation, timing, height and shading. • We don’t repeat the same crop family two years running: lettuce, brassicas, spinach/beets/chard. • Because everything happens faster in a hoophouse, we are growing multiple crops in each bed each year. • We look at the sequence of crops, rather than the number of years since the same crop was grown. • We hope that the part of the year spent growing other crops contributes to a speeded up version of the time needed away from that crop in an outdoor rotation.
  65. 65. Pests Credit In cooler weather, our worst hoophouse pests are aphids and vegetable weevil larvae. • We spray the aphids with soap 3 times, 5 days apart, or later in the season we bring in ladybugs. • VWL live in soil, come out at night to eat holes in brassica leaves. We killed them with Spinosad.
  66. 66. 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.
  67. 67. 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
  68. 68. 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.
  69. 69. 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.
  70. 70. Resources – General ATTRA  Market Farming: A Start-up Guide,  Scheduling Vegetable Plantings for a Continuous Harvest,  Season Extension Techniques for Market Farmers.  Cole Crops and Other Brassicas: Organic Production  SARE A searchable database of research findings:  Season Extension Topic Room  The organic agriculture community with eXtension. Publications, webinars, videos, trainings and support. An expanding, accessible source of reliable information.  Growing Small Farms: Debbie Roos keeps this site up to the minute. Click Farmer Resources  Penn State Extension High Tunnels site:  tunnels Lots of info, also a Listserve.
  71. 71. Resources - slideshows Many of my presentations are available at Search for Pam Dawling.  Cold-hardy Winter Vegetables  Producing Asian Greens  Production of Late Fall, Winter and Early Spring Vegetable Crops  Succession Planting for Continuous Vegetable Harvests Other slide shows I recommend:  Alison and Paul Wiediger : why-grow-in-high-tunnels and at least 11 more.  Mark Cain Planning for Your CSA: (search for Crop Planning)  Tom Peterson Farm Planning for a Full Market Season market-season.pdf  Brad Burgefurd, Cultural Practices And Cultivar Selections for Commercial Vegetable Growers. practices-and-variety-selection
  72. 72. Resources – books and seeds  Walking to Spring, Using High Tunnels to grow produce 52 weeks a year, Alison and Paul Wiediger  Knott’s Handbook for Vegetable Growers, Maynard and Hochmuth  The New Seed Starter’s Handbook, Nancy Bubel, Rodale Books  The New Organic Grower, Eliot Coleman, Chelsea Green  Grow Your Own Chinese Vegetables, Geri Harrington, 1984, Garden Way Publishing. Includes the names for these crops in different cultures.  Growing Unusual Vegetables, Simon Hickmott, 2006, Eco-Logic books, UK.  Oriental Vegetables: The Complete Guide for the Garden and Kitchen, Joy Larkham, revised edition 2008, Kodansha, USA  Wild Garden Seeds  Even ‘Star Farm specialize in cold-tolerant varieties.  Evergreen Seeds’ helpful clickable list of Asian greens:
  73. 73. The Hoophouse in Fall and Winter ©Pam Dawling 2015 Twin Oaks Community, Central Virginia Author of Sustainable Market Farming Published by New Society Publishers