Winter Kill Temperatures of Winter-Hardy Vegetables 2016

November sky Photo Ezra Freeman
November sky
Photo Ezra Freeman

March 2020 Update: click this link.

I’ve just updated my “Winter-kill” list, adding information from last winter to update for this winter’s planning. For several years, 2015, 2104, 2013, 2012 my friend and neighboring grower Ken Bezilla of Southern Exposure Seed Exchange and I have been keeping records of how well our crops do in the colder season. Ken provided much of the original information, and has suggested the morbidly named Death Bed idea: set aside a small bed and plant a few of each plant in it to audition for winter hardiness. Note each increasingly cold minimum temperature and when the various crops die of cold, to fine tune your planting for next year (and send me an email!) This year I have added some cover crop hardiness temperatures. We are in zone 7a, with an average annual minimum temperature of 0-5°F (-18°C to -15°C).

It’s worth noting that in a hoophouse plants can tolerate lower temperatures than those listed here: they have the pleasant daytime conditions in which to recover. Salad greens in a hoophouse in zone 7 can survive nights with outdoor lows of 14°F (-10°C). All greens do a lot better with row cover to protect them against cold drying winds.

Also note that repeated cold temperatures can kill off crops that can survive a single dip to a low temperature, and that cold winds, or cold wet weather can destroy plants quicker than simple cold. Here are some starting numbers of killing temperatures, although your own experience with your soils, microclimates and rain levels may lead you to use different temperatures:

Cultivating lettuce in the hoophouse Photo McCune Porter
Cultivating lettuce in the hoophouse. Russian kale at the back, pak choy in the foreground.
Photo McCune Porter

April 2018 note: Since this 2016 post, I updated this list for 2018 Click this link.

2019 Note: I posted my 2019 list of Winter Kill Temperatures of Cold-Hardy Vegetables on April 30, 2019

2016 List

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): Many cabbage, Sugarloaf chicory (takes only light frosts), radicchio.

25°F (-4°C): Chervil, chicory roots for chicons, and hearts, Chinese Napa cabbage (Blues), dill, endive (hardier than lettuce, Escarole more frost-hardy than Frisée), annual fennel, some mustards and Asian greens (Maruba Santoh, Mizuna, most Pak Choy, Tokyo Bekana), onion scallions (some much more hardy), radicchio.

22°F (-6°C): Arugula (may survive colder than this), large leaves of lettuce (protected hearts and small plants will survive even colder temperatures).

20°F (-7°C): Some beets, broccoli heads (maybe OK to 15F), some cabbage heads (the insides may still be good even if the outer leaves are damaged), celeriac, celtuce (stem lettuce), some head lettuce, some mustards/Asian greens (Tendergreen, Tyfon Holland greens), radishes, most turnips with mulch to protect them (Noir d’Hiver is the most cold-tolerant variety).Large oat plants will get serious cold damage. Oats seedlings die at 17°F (-8°C). Canadian (spring) field peas are hardy to 10-20°F (-12 to -7°C).

15°F (-9.5°C): Some beets (Albina Verduna, Lutz Winterkeeper), beet leaves, some cabbage (Kaitlin, Tribute), celery (Ventura) with rowcover, cilantro, endive, fava beans (Aquadulce Claudia), Russian kales, kohlrabi, some lettuce, especially medium-sized plants (Marvel of  Four Seasons, Olga, Rouge d’hiver, Tango, Winter Density), curly leaf parsley, flat leaf parsley, large leaves of broad leaf sorrel, turnip leaves, winter cress.

12°F (-11°C): Some beets (Cylindra,), some cabbage (January King, Savoy types), carrots (Danvers, Oxheart), most collards, some fava beans (not the best flavored ones), garlic tops if fairly large, most fall or summer varieties of leeks (Lincoln, King Richard), large tops of potato onions, rutabagas (if mulched), Senposai leaves (the core of the plant may survive 10F), some turnips (Purple Top), winter radish including daikon (may survive colder).

Young senposai in the hoophouse Photo Wren Vile
Young senposai in the hoophouse
Photo Wren Vile

10°F (-12°C): Beets with rowcover, Purple Sprouting broccoli for spring harvest, Brussels sprouts, chard (green chard is hardier than multi-colored types), a few varieties of cabbage (Deadon), some collards (Morris Heading can survive at least one night at 10F), Belle Isle upland cress, some endive (Perfect, President), young stalks of Bronze fennel, probably Komatsuna, some leeks (American Flag, Jaune du Poiteau), some head lettuce under row cover (Pirat, Red Salad Bowl, Salad Bowl, Sylvesta, Winter Marvel), large leaves of savoyed spinach (more hardy than flat leafed varieties), Tatsoi, Yukina Savoy. Oats cover crop of a medium size die around 10°F (-12°C). Large oat plants will die completely at 6°F (-17°C) or even milder than that.

5°F (-15°C): Brussels sprouts, Garlic tops if still small, some kale (Winterbor, Westland Winter), some leeks (Bulgarian Giant, Laura, Tadorna), some bulb onions, potato onions and other multiplier onions, some winter radishes (Daikon, China Rose, Shunkyo Semi-Long survive 10°F/-12°C), smaller leaves of savoyed spinach and broad leaf sorrel. Many of the Even’Star Ice Bred greens varieties are hardy down to 6°F (-14°C).

0°F (-18°C): Chives, some collards (Blue Max, Winner), corn salad (mache), garlic, horseradish, Jerusalem artichokes, a few leeks (Alaska, Durabel); some bulb onions, some onion scallions (Evergreen Winter Hardy White, White Lisbon), parsnips (probably even colder), salad burnet, salsify, some spinach (Bloomsdale Savoy, Olympia, Tyee). Crimson clover is hardy down to 0°F (-18°C) or slightly colder

Even Colder: Vates kale survives 0°F (-18°C), although some leaves may be too damaged to use. Leaves of overwintering varieties of cauliflower are hardy down to -5°F (-19°C). Walla Walla onions sown in late summer are hardy down to -10°F (-23°C). Narrow leaf sorrel, Claytonia and some cabbage (January King?) are said to be hardy in zone 3,  -30°F to -40°F (-34°C to -40°C).

Austrian Winter Field Peas and Crimson clover (used as cover crops) are hardy down to -10°F (-23°C). Hairy vetch is hardy to -15°F (-26°C), some say down to -30°F (-34°C). Dutch White clover cover crops are hardy down to -20°F (-29°C) or even -30°F (-34°C). Winter wheat and winter rye (cover crops) are hardy to -40°F (-40°C).

Vates kale in the fall. Photo Bridget Aleshire
Vates kale in the fall.
Photo Bridget Aleshire
Vates kale after a winter of much harvesting. Photo Twin Oaks Community
Vates kale after a winter of much harvesting. Photo Twin Oaks Community

Public speaking, Garden Calendars, Winter-kill temperatures

GFM-January2015-cover-300pxThe January issue of Growing for Market magazine is out, along with my article about giving talks. I want to encourage more gardeners and farmers to “grasp the nettle” and offer to give a workshop on a topic you know about. I speak at about 9 or 10 events each year now, but I used to be completely terrified of public speaking. So, if I can do it, I think you can too! It’s a way of sharing useful information to help improve the quality and quantity of fresh healthy food in the world. It’s a part of a co-operative model of spreading information rather than hording it. It can be a way of “singing for your supper”, as conference speakers usually get free registration to the conference and accommodation. Sometimes traveling expenses are covered, sometimes meals, sometimes there’s an honorarium. Start small and local and offer a farm tour, perhaps after joining a local group like CRAFT (Collaborative Regional Alliance for Farmer Training). At Twin Oaks, we have been part of the Piedmont CRAFT group of central Virginia. Each month in the main season, there is a gathering at one of the involved farms, with a tour and a discussion topic. Todd Niemeier of the Urban Agriculture Collective of Charlottesville was the starting energy for that group too.

The January Growing for Market also contains a helpful article about using hot water seed treatments to reduce seed-borne diseases (by Chris Blanchard). The idea of soaking seeds in hot water for half an hour or even more, and then drying them out to sow later can be daunting. But with this step-by-step guide and encouraging reports from different growers, it all becomes manageable.

Andrew Mefferd has branched out from his detailed series on hoophouse tomato growing, to talk about growing eggplant in hoophouses or greenhouses. Very useful for people in climates colder than ours here. And, of course, there are tips that are helpful to people who thought they had already read everything about growing eggplants!

Kyle and Frances Koehn write about the Fresh Fruit and Vegetable Program (FFVP), a federally assisted Farm to School Program suited to small-scale growers. FFVP supplies elementary schools with fresh produce as snacks (so you don’t have to grow enough to supply a whole lunch every day). For the authors, this has been a great fit with winter leafy greens grown in their NRCS funded high tunnel. Search for the FFVP program in your state. Virginia, for example, covers FFVP in their Farm to School Program Resource Guide.

Lynn Byczynski writes about growing heirloom mums, and Valley Oak Tools advertises the debut of their Electric Cub crop cultivating tractors.


Flats of seedlings in our greenhouse. Credit Kathryn Simmons
Flats of seedlings in our greenhouse.
Credit Kathryn Simmons

And, here we are with another new year, thinking about the next growing season. I recently read a post in Margaret Roach’s  A Way to Garden. She has gathered regional garden calendars. I found the one from West Virginia Extension Service particularly helpful and attractively set out. This put my in mind to give the link to our Twin Oaks Garden Calendar for all vegetable growers in the mid Atlantic. Especially as one of my local farmer friends asked me about it recently. And let’s not forget that on Saturday 1/17 we are scheduled to start some cabbage, lettuce and mini-onions!

Red marble mini-onions. Credit Johnnys Selected Seeds
Red Marble mini-onions.
Credit Johnnys Selected Seeds

Part of my attention at this time of year goes to Winter-kill temperatures for different crops. We’ve had a couple of unusually-cold-for-this-early-in-winter nights already.  What did I learn?

At 14F, Cylindra beets were OK, as were Tribute and Kaitlin cabbages. The remaining broccoli shoots became rubbery.

At 10F, some of the Tribute and Kaitlin cabbage heads were damaged; Some carrot tops were killed, but the roots were OK; Senposai was damaged, but not killed; the winter radish (daikon, China Rose and Shunkyo Semi-long) were OK; the celery is over; most of the chard leaves were killed, and the medium-sized non-headed oats cover crop took quite a hit. Outredgeous lettuce is not as cold-tolerant as I thought. Olga was damaged, but Salad Bowl, Red Salad Bowl, Pirat, Red Cross, Sylvesta and Winter marvel were fine under hoops and thick rowcover.

Before it got any colder, we harvested the last of the Melissa savoy cabbage and the bed of Deadon cabbage (we could have covered it if we’d really wanted to preserve it for longer, but we were ready for some fresh cabbage – it does make the stored cabbage look rather wan.

Lettuce bed. Credit Wren Vile
Lettuce bed. Salad Bowl and Outredgeous in early spring.
Credit Wren Vile