Think Kale is the King of Cold Hardy? Think again.
A wide variety of garden vegetables tolerate freezing just as well as, and some even better than most kale varieties:
Cold temperatures stimulate sugar accumulation in carrots, acting as a natural antifreeze that protects the roots from freeze damage. Sow carrots through to late summer and you’ll still be harvesting them into late fall, and then leave them in the ground for steady harvests throughout the winter. Green carrot tops are hardy to at least 18 °F (-8 °C), but the roots can withstand even colder temperatures. To make harvests easier, either heavily mulch carrots when really cold temperatures arrive or cover them with a low tunnel or cold frame.
Spinach is actually a tough little plant and will over-winter without protection. Growing slowly through winter it’ll bounce back in early spring. Spinach can look rather rough in winter without some protection, so grow it under cover if winter salads are your aim. Savoy (deeply crinkled) types are much more cold-hardy than flat-leaf varieties.
If you’ve planted garlic in the fall (as you should), you know that the tops are remarkably resilient to hard freezes. Leeks, a close cousin, are also champions of winter gardens. Because leeks are not sensitive to day length, like many other alliums, they will continue to grow well during the shorter days of winter. Note that there is considerable variation in the freezing susceptibility of leek varieties; although most leeks are very cold-tolerant, the darker, blue-green varieties are most likely to survive dips to 0 °F (-18 °C).
Collards are superior to kale when it comes to freeze-tolerance; when Lacinato and Red Russian kale are wilted and brown, collards continue to hold. Collard variety Blue Max is a favorite, with high yields, and the greatest degree of cold-hardiness (down to 0 °F/-18 °C).
Like carrots, parsnips accumulate sugars with fall’s first frost and become sweeter. They hold well in the ground throughout the entire winter. To grow parsnips for winter harvests, plant no later than early May as they can take up to 130 days to mature. Parsnips are generally tolerant to 0 °F (-18 °C) but cover when hard freezes occur. The seed quickly loses viability so it’s wise to buy fresh seed annually.
Immature plants are generally more cold-tolerant than mature plants, and grown under the protection a cold frame or low multilayered fabric tunnel, they can survive when temperatures dip to 10 °F (-12 °C). It’s best harvested in the baby leaf stage. Generally, heat and drought-tolerant varieties are also the most cold-hardy.
The flavor is improved by frost, and insect pest problems are generally fewer. Not all varieties do well in a hard freeze but there are several varieties that hold well left unprotected in the ground. Similar to spinach, the most cold-tolerant cabbages are savoy types with deeply crinkled leaves. Overwintered cabbage will need to be planted in late summer to have time to mature.
Rutabaga lose much of their spiciness and accumulate sugar when they mature in cold weather. Not as cold-hardy as other crops, so if growing through the winter they will need protection. As the roots are near the top of the soil try mulching heavily, or select a variety with thicker skins and deeper root production.
Remarkably cold-tolerant, surviving to 15 °F (-10 °C) without protection. Green or white chards are mostly more cold-hardy than the multicolored variety, Bright Lights. In extreme winter conditions, protect in a cold frame or low tunnel. Optionally, harvest all the leaves and cover the remaining chard crown with a thick layer of mulch. The plant will survive the winter and produce new growth in the spring.