Know your frost date and the days to plant maturity

No matter what season extender you use, there are two important things to remember when planting fall and winter edibles: the approximate date of the first hard frost in your region and the days to maturity for each crop you plant. The Old Farmer’s Almanac lists frost dates for most parts of the country. And days to maturity will be listed in the seed catalog or on the packet. This information is important because the growth of most plants comes to a standstill when day length drops below 10 hours. As a result, it is important to be sure that crops are at the right stage of maturity when they have less light.

To ensure that winter crops have enough time to grow and reach a harvestable size, I add an extra week or two to the maturity date for the selected edible. ‘Winterbor’ kale, for example, is an extremely cold-tolerant hybrid. It is ready to harvest as a baby crop about 60 days after seeding and after 80 days for a mature plant. If I want a mature winter crop of ‘Winterbor’, I need to take 80 days, tack on an extra week to account for the shorter days, and count backward from my first hard-frost date to determine when to seed it.

Season extenders protect crops from inclement weather

Season extenders stretch the growing season by weeks or months. These four examples afford gardeners extra protection for times when nature isn’t especially cooperative.

Cloches have been used for centuries by clever gardeners to extend a harvest. Also known as hot caps, cloches are miniature greenhouses placed over plants to protect them from inclement weather. I use cloches in two ways: to shield crops for one or two days from imminent frost, hail, or snow; and as an incubator to shelter early-planted or tender crops for up to six weeks.

In the case of imminent bad weather, any type of container can be an effective short-term cloche; a bucket or large jar works well. Because this protection won’t be on the plants for more than a day or two, it doesn’t need to be translucent. For longer protection, the cloche needs to be made of a clear material, like glass or plastic, to allow good light transmission. Cloches should be removed or vented on mild days (when temperatures exceed 40°F [4°C]) to protect plants from overheating. An unvented cloche will trap heat and humidity, and if left on for too long in warm weather, it will scorch the plant beneath it.

Row covers insulate newly seeded or transplanted crops

Row covers are gauzy materials that are extremely effective at insulating newly seeded or transplanted veggies from light frost, cold weather, and pests like birds or deer. In spring and early autumn, light- to medium-weight fabrics can be laid directly on top of crops. As fall morphs into winter, I switch to heavyweight covers and float them on mini hoops, along with a layer of greenhouse plastic to shelter cold-season edibles, like kale, Swiss chard, leeks, and spinach. Heavyweight row covers offer more insulation than light- or medium-weight covers, but they don’t allow as much light to pass through. A heavyweight material placed directly on vegetables that are actively growing in spring or autumn could delay or damage the crops. I, therefore, save heavyweight covers for winter, when my vegetables are hibernating.

—Niki Jabbour is a food gardener, a radio host, and the author of The Year-Round Vegetable Gardener. She lives near Halifax, Nova Scotia, where she and her family harvest vegetables throughout winter.