Every fall since I began gardening, I work to dispel the myth that the growing season is over, and that frosts will kill anything remaining in the garden.
Not all plants are the same. Tomatoes, peppers, squash, corn, and other crops that thrive on hot temperatures are from hot climates. They didn’t need to survive the cold – instead, they needed to protect from heat. However, broccoli, carrots, garlic, rhubarb, and many other crops came from cool climates. Their systems work differently in the cold – not only do they survive cold temperatures, but they taste better when they get cool in the fall and winter!
It’s Not Frost That Kills, It’s Freeze
The night the first frost comes around in the fall, many people rush out to yank their tomato plants and bring them inside. After that night, it often gets warmer and sometimes there isn’t another frost for several weeks! It’s highly likely all those tomatoes hanging from rafters after that first frost would have been just fine outside through the first frost. The reason is that the first frost is often not a killing frost.
What kills the plants is not frost specifically, but is the internal temperature of plant tissue – once it freezes, the plant dies. Have you ever put a bottle of beer or soda in the freezer to cool it down quickly, and then forgot about it, until you heard a loud crash in the freezer several hours later? The loud crash is the glass breaking because the liquid inside the bottle expanded as it cooled. This is essentially what happens to the cells in a tomato plant when it gets cold.
Generally the first frost doesn’t quite freeze the plant because it happens at just barely 32F, and doesn’t stay long. However, the first freeze – or hard frost – often rolls in with much lower temperatures and stays cold much longer, usually killing the cells of tropical plants.
However, many plants do not have the fragile cellular structure of these tropical plants.
Deciduous trees, bushes, and vines go dormant in the winter by losing their soft tissue (leaves), and waiting until spring before producing them again.
Root crops (beets, carrots, radishes, parsnips, daikon, rutabagas) store all of the energy from their leaves into their roots as it gets cooler, and the ground gives them protection against the freezes.
Cole crops (broccoli, brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustards, turnips, watercress) can often survive temperatures below 20F. That means those of us in temperate climates can generally grow them throughout the winter (they don’t grow a whole lot in the winter, but they don’t die and you can continue to pick fresh crop), where others can often grow them with a row cover for protection. These biennial plants are made to last through the winter, so that they can bloom and produce seed in the spring.
Alliums (leeks, onions, garlic, shallots, scallions, chives) can survive very low temperatures (-30F). These perennials are generally planted 2-3 weeks before first frost, and rely on the spring warmth to start putting their energy into bulbs. Garlic in particular can benefit from a layer of mulch over the winter, to keep them protected through cooler temperatures.
Other perennials (asparagus, rhubarb, oregano, rosemary, sage, jerusalem artichokes, citrus) – there are many perennials that either continue to produce over the winter, or that go dormant over the winter to produce in early spring. I highly recommend checking out some of these, as they are incredibly rewarding when the rest of the garden is sparse.
Other crops I’ve had success growing in winter (parsley, cilantro, dill, spinach, endive, sorrel, lettuces, fennel, fava beans) – the key for many of these is to get them growing before it gets cold, as most plants don’t grow very much in cold weather. Thus, plant them 4-6 weeks before frost, and then harvest throughout the winter.
For More Information
There are many other plants you can continue to grow or store in the garden with often just a bit of protection. Check out “How To Grow A Four-Season Garden” for many tips on how to do this effectively!
Anything To Add?
Avid gardeners, what else would you add here? Other crops you’ve had success growing in winter?