Extend Your Harvest with Cold Hardy Crops

By Susan Littlefield

Shortening days and chilly nights are unmistakable signs of the change of seasons as summer gives way to fall, and then fall to winter. Those first frosty nights finish off the tender warmth lovers like tomatoes, beans, and cucumbers. But there are many crops that shrug off light to moderate frosts, keeping you in fresh veggies through early to mid-fall. And a few especially hardy crops keep bearing until temperatures drop down to ″hat and mittens″ weather. Giving cold-tolerant crops some protection with a cold frame, low tunnel, or even just some mulch can extend the harvest even longer.

Degrees of Frost

You may hear the weatherman or other gardeners talking about a light frost and a hard frost or freeze. But just what does this mean in terms of temperatures? While there are various interpretations of these terms, generally a light frost refers to an overnight event when the temperatures dip down between 32 and 30 degrees F. The first light frost is often a radiational frost that occurs when skies are clear and winds calm. This will knock out warmth lovers like beans and basil. But many other more cold-tolerant crops such as broccoli, lettuce, spinach, beets, kohlrabi, mustard greens, cabbage, Swiss chard, and hardy greens like arugula and mizuna will survive until temperatures reach down into the 28-25 degree F range. These sturdy crops can keep you enjoying fresh food from your garden until a hard frost or freeze hits, often when a large mass of cold air moves in. But even after a hard freeze, there are still a few tough crops, like kale, collards, and Brussels sprou ts, that may continue to provide food for the table even when there's snow on the ground!

Here are just a few of the cold tolerant crops we carry.

'Long Island Improved' Brussels Sprouts (90 days) —Great as a fall crop, these sprouts have an unusually fine flavor.

'Red Acre' Cabbage' (74-90 days) —Resistant to yellows and splitting, this variety produces hard, round, 5-7″ diameter, deep red-purple heads.

'Early White Vienna' Kohlrabi (55-60 days) —Harvest the green, fine-textured bulbs when they are about 2 inches in diameter for maximum tenderness.

'Georgia' Collards (80 days) — These leafy, non-heading plants produce large, crumpled, blue-green leaves that are tops for nutrition.

'Tendergreen' Mustard Greens (40 days) —Large plants grow quickly to produce thick, dark green leaves with a spinach mustard flavor.

Mizuna (40 days) —This finely-cut, mild flavored salad green is very hardy and will regrow after cutting.

Protection Strategies

Offering your plants some protection from frost and cold temperatures can extend the harvest of cold-tolerant crops into late fall or longer. An early dip in temperatures may be followed by weeks of warmer weather, so even temporary covers can be beneficial to some crops. And more elaborate protection strategies can keep homegrown produce on your table for weeks or, in some cases, even months longer than for unprotected crops. Here are some ideas for extending the garden season.

Temporary Plant Covers: Covering your plants with woven fabric such as row cover fabric or even old sheets or blankets when a sudden dip in overnight temperatures is forecast can provide up to 5 degrees F of protection. Simply drape covers over plants or, for the greatest protection, support the covers with stakes or hoops so that they don't rest directly on plants. Put covers in place in late afternoon and remove them early the next morning.

Cold Frame: Sow plants such as lettuce, spinach, arugula, chard, mustard greens, green onions, beets,turnips, and carrots in a cold frame in mid to late summer (even early fall for fast-maturing greens). Keep the cold frame open until cold weather arrives, then close the lid to keep heat in. You may need to open the top at least part way on sunny days, but close the frame back up before the sun sets to trap daytime heat. Throw an old blanket over the top on especially cold nights to hold heat in.

Construct a seasonal, inexpensive, and easy to build cold frame out of bales of straw and a light-transmitting cover, such as a piece of polycarbonate or recycled storm windows. This is a great way to protect tall crops like leeks and kale and keep them available for harvesting late into the season. Simply surround the plants with bales piled as high as needed, top with the cover, and you're done! For extra protection and continued harvesting, fill in around plants with straw or leaves that won't mat down, such as oak leaves. Next spring you can recycle the straw or leaves as mulch or add them to your compost pile.

Low Tunnels: Constructed from heavy weight row cover fabric stretched over hoops, low tunnels make it easy to protect taller growing and larger plants like broccoli, cabbage, kale, and collards, but are also suitable for protecting the lower growing plants suggested for cold frame growing. Get your hoops in place in early fall; then drape them with row cover fabric anchored to the ground on the sides when temperatures begin to fall.

Mulch: Fill large plastic trash bags with straw, hay, or leaves. Then place the bags two feet deep on top of the bed where your root crops are growing. This will insulate the soil and you'll be able to go out in late fall and early winter, pull back the bags, and continue your harvest of carrots, beets, and parsnips. Extend the bagged mulch out about a foot and a half on each side of the planting.

Question of the Month: Preserving Gourds

Q: I grew lots of colorful gourds in my garden this summer. What's the best way to make them last?

A: Harvest your gourds when both their stems and the tendrils growing from the stems are dry and the surface of the gourd is hard, but before frost hits. Cut the fruits from the vine, leaving a few inches of stem. Be sure to handle them carefully so they don't get bruised, and don't pick them up by their stems, which might break off. Wash the gourds with a solution of 1/2 cup of white vinegar in 2 quarts of water to remove fungi and any dirt. Then spread the gourds out on a raised screen in a well-ventilated spot to dry, turning them regularly. Drying time will depend on the size of the gourds, but usually takes at least 4 weeks for thin-shelled gourds; longer for ones with thick shells. When completely dry, the gourd will feel lightweight and you'll be able to hear the seeds rattle inside when you shake it. Once it's dry, clean the surface of the gourd again with some rubbing alcohol. For the longest preservation, seal the surface of the dried gourd with clear shellac or paste wax.

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