Winter is not normally a time we think of for growing food or eating fresh green vegetables, but the reality is that it is possibly the best time for doing so. Most members of the brassica family — all those cabbages, broccolis, and so forth — are more fans of frigid weather than summer heat. In fact, many of them aren’t at all interested in growing in July. But, give them a little bed and some shelter, and they’ll give you fresh greens through the winter.
Whereas many of our common, homegrown garden vegetables — tomatoes, peppers, cucumbers, beans, and squash — wither at the first hints of frost, kale is one of the most revered cold-hardy vegetables. In fact, the flavor actually improves in winter as the freeze knocks some of the bitterness out of it.
Not only is kale a great wintertime crop, but it is also a perfect vessel for providing a heavy dose of vitamins and minerals. Plus, fresh green vegetables are much more delicious than the typical winter options of frozen or canned. With just a little preparation and the sun’s power, kale can provide fresh greens for delicious meals over the entire season.
The Colder Limits of Kale
There are limits to the temperatures kale can withstand, but the good news is that, for the most part, anyone in the contiguous United States can have fresh kale in the winter. For those in USDA zones 7-9, which includes all of the Southern states and many of the Coastal states (up to about Virginia), it might be possible to simply grow kale year-round. As long as frosts and snows aren’t particularly heavy, it will survive. In the other states, it’s still possible to grow it, but we will need to provide a little extra protection. It can survive temperatures down into the lower 20s, which is easy to provide even without a heating system, but it will need a little structural support from the weight of the ice and snow.
Framing for Warmth
For climates with more snow and frost, it’s necessary to protect winter kale in cold frames. Cold frames are basically wooden boxes with no bottom and a glass top. Instead of a bottom, the box sits atop a garden bed, and the glass top allows the sun to warm the box and keeps the snow and frost off the plants. Most gardeners like to build their cold frames with tops that have a slight pitch, with the lower side facing south to allow in more sunlight. The slope also helps with shedding off snow and rain. For kale, the box will need to be roughly two-feet tall, but the surface area can be based on what materials are at hand and the size of the bed.
What Kale Likes in a Garden
Kale, like any plant, has particular preferences. It likes mildly acidic soil, ideally in the 6.0 to 6.5 pH range, which is typical for most gardens. Like any leafy vegetable, kale also likes the soil to be high in nitrogen, which encourages leaf growth. Soils should also always be rich in organic material. While mature plants can thrive in colder temperatures, the best time to plant kale is when the soil is around 60-65 degrees Fahrenheit, which is typically in early autumn. Kale also likes things to remain moist, so be sure to provide a thick layer of mulch and to check the soil regularly.
Working the Winter Garden
With winter gardens, it is important to have a few know-how tips in the pocket. For one, kale will likely freeze overnight, even in a cold frame, and it’s best to wait until the leaves have thawed before harvesting them. The need for regular watering will significantly decrease as the temperature does because the plants either stop or significantly slow down production. In other words, it’s best to grow the greens earlier than in the depths of winter, with the idea being to keep them alive, i.e. fresh, in the coldest months.
Lastly, in a cold frame situation, and with any vegetable, be sure to open the lid up a few times a week, enough for the air to change. As the temperature warms, it will be necessary to vent the cold frames by propping the tops open during the day. Warm snaps can destroy a good winter crop, and this is particularly evident in the spring, as daytime temperatures rise significantly, but nighttime temperatures still call for protecting the plants.
Enjoy the Winter
For those who make a little extra effort in the autumn, the payoff in the winter is ten-fold. Once temperatures drop, winter gardens are very easy to maintain. Pests aren’t such a big problem, watering isn’t all that necessary, and gardeners just need to harvest regularly. It can’t get much more ideal than low-maintenance, fresh, homegrown kale in the winter!
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