Cold Tolerance of Vegetables

Okiedawn OK Zone 7March 26, 2009

In a thread about the weather, Okiehobo asked about the cold tolerance of some of the cool season vegetables that many of us already have planted in our gardens (and rightfully so, depending on where you live in OK).

So, I thought I'd post this list showing the different degrees of cold hardiness. With the forecast snowstorm and large snow accumulations expected in northwestern OK for sure and perhaps all the way down to southern OK, covering up anything in the veggie garden is a good idea. And, if it stays cold enough long enough, even covering up the plants may not save them. One good thing is that snow itself acts as an insulator.

This thread is about veggies only. If anyone has enough flowers in the ground, we can have a similar discussion on them in a separate thread to keep it from getting too confusing.

VERY COLD-HARDY VEGETABLES:

None of the vegetables we grow can withstand very cold temperatures (sub-freezing) for a long period of time. However, the ones listed below can withstand freezing temperatures for a short period of time. You can't really say that a specific vegetable tolerates a specific temperature for a specific number of hours, though, because there are just too many variables.

In general, these are the vegetables that we can plant 4 to 6 weeks prior to our average frost-free date.

Asparagus

Collards

Endive

Kale

Kohlrabi

Lettuce

Mustard

Onion (from seed and sets)

Peas

Potatoes

Rhubarb

Rutabaga

Salsify

Spinach

Turnip

FROST-TOLERANT:

These are the vegetables that can withstand light frosts and can be planted 2-3 weeks before your average frost-free date.

Beets

Broccoli

Brussels Sprouts

Cabbage

Carrots

Cauliflower

Celeriac

Celery

Chard

Chinese Cabbage

Jerusalem Artichokes

Onion (from plants)

Parsnip

Radish

TENDER:

These plants will be killed or injured by even a light frost. However, they will tolerate somewhat cool (but not cold) soil and can be planted outside on or after your frost-free date provided you can cover them up if frost or a freeze threatens. (Keep in mind that on a cold, clear night, frost can form and injure these plants at temps as high as 38-39 degrees.)

Snap Bean

Sweet Corn

Tomato

WARMTH-LOVING:

These vegetable cannot tolerate any cold weather and do not like cold soil or cold air. If started from seed, they must have warm soil to germinate. If exposed to cold temperatures they often are stunted and unproductive for the entire growing season. Generally the earliest they are planted out is 2-3 weeks after your average frost-free date:

Lime Bean

Cucumber

Eggplant

Muskmelon and true Cantaloupe and other melons

Okra

Pepper

Pumpkin

Squash, Summer

Squash, Winter

Sweet Potato

Watermelon

In general, it is always preferable to cover up everything you can when snow is in the forecast. You can use any type of mulching material you have handy. For added protection, toss a row cover-type frost blanket over the mulched bed, or use old blankets or curtains, sheets, sleeping bags, etc. In general, plastic is not advised because anywhere the plastic touches the plant, freeze damage is likely to occur. The exception would be if your plants are completely covered by hay or straw or some other mulch and then the plastic is throw over that mulch.

Some of you who garden in a significantly colder area than mine (I'm zone 7b) might have more to add about what you do for frost, freeze, sleet or snow protection.

As for fruit trees, there again, many variables are involved are involved and it is almost impossible to know with a certainty if a certain temperature is going to damage some or all of your fruit. I did post a chart on a previous thread that somewhat details the amount of damage that occurs at different stages of bloom/fruit development and different temperatures.

If you have seedlings (not wintersown ones, regular ones) on/in a porch, enclosed but unheated porch, garden shed, garage, etc., you probably should move them indoors for the next 2-3 nights if it is at all possible.

Batten down the hatches, y'all, 'cause Old Man Winter is sneaking in to visit sweet and young Miss Spring.

Dawn

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shebeest(7)

This question doesn't concern vegetables, but what should we do about blooming shrubs. My azaelias are about to bloom, can I cover them with a large garbage bag or can they not tolerate plastic either if it freezes?

    Bookmark   March 26, 2009 at 10:03PM
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shebeest(7)

Dawn,

I should have read further on the forum before I posted my question. I saw your answer about plastic on another question, so please disregard my post.

Susan

    Bookmark   March 26, 2009 at 10:10PM
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Okiedawn OK Zone 7

Susan,

No problem. Anything that is cloth would be better than plastic.

If you wanted to throw a blanket over them, you could, but whether or not it will help is iffy. It depends on how cold y'all get, how long you stay cold, and how much snow or ice falls.

Dawn

    Bookmark   March 27, 2009 at 12:10AM
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pennye

I have planted 20 brussels,and 20 broccoli plants. Weather
is calling for 20 degress. should I dig up all the plants put them in buckets and bring them in,or fill the buckets with leaves to put over the plants.

    Bookmark   April 6, 2009 at 12:27AM
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Okiedawn OK Zone 7

Penneye,

I think I would just try to cover them up the best I could if the 20s are just for a night or two. Digging up the plants would disrupt their growth and they might be set back enough that they wouldn't survive or might survive but not grow well. I'd cover them up with buckets/leaves and heap more leaves on top of the ground around the buckets. If you have any unused blankets or sleeping bags, I'd be tempted to throw those over the buckets and leaves for an extra layer of protection. Just be sure to uncover everything in the morning before the sun rises too high in the sky so your plants won't bake.

Also, before you cover the plants, make sure the soil is moist because dry roots suffer freeze damage more quickly than moist roots.

Good luck,

Dawn

    Bookmark   April 6, 2009 at 9:47AM
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rob_thompson(5)

For years I have planted Broccoli out 6-8 weeks before my last spring frost and it has easily survived 20 degree hard freezes. My fall Brussel Sprouts always survive well into the winter here in Zone 5.

    Bookmark   May 13, 2009 at 3:15PM
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