CORVALLIS – Not ready to hang up your gloves and spade yet? The intrepid gardener still has a chance to plant some cold-hardy vegetables that can be harvested next spring. But don’t dawdle.

“Winter gardening is a risky business,” said Jim Myers, a plant breeder and researcher at Oregon State University. “One year with a mild winter, it might work, but another year with more severe weather might not. If you plant some cold-hardy vegetables from mid-August to early October — depending on the crop — there’s a good chance you’ll have a harvest in the spring. They say farming is a gamble… some years more than others.”

Cold weather doesn’t kill these hardy plants, it just slows their growth. For every 18-degree increase in temperature, growth doubles, but that guideline only applies to an air temperature range of 40 to 98 degrees, Myers said. If you plant cold-hardy vegetables from mid-August to early October, there’s a chance they’ll mature by next spring if they survive the winter in a vegetative state without multiplying.

According to Myers, the most resilient vegetables that can withstand severe frost or air temperatures below -28 °C include spinach, onions, garlic, leeks, rhubarb, turnips, broccoli, kohlrabi, kale, white cabbage, collard greens, Brussels sprouts, lamb’s lettuce, arugula, fava beans, radishes, mustard greens, winter peas and turnips.

Semi-hardy vegetables that can tolerate light frosts at air temperatures in the range of 28 to 32 degrees include beets, carrots, parsnips, lettuce, chard, garden peas (before flowering), Chinese cabbage, endive, radicchio, cauliflower, parsley and celery. In beets, carrots and parsnips, the tops will die back, but the roots will tolerate lower temperatures. In plants that form a head, such as radicchio and other chicory varieties, the outer leaves may die back in colder temperatures, but these can be pulled off to leave an undamaged head inside.

Vegetables that contain the pigment anthocyanin, which gives them a bright red or purple color, are more resistant to blight caused by winter rains, Myers said. These include purple broccoli, Rosalind broccoli and purple kale.

Snow insulates

If you live in a part of the state that gets snow for extended periods, the fluffy white stuff acts as an insulating mulch and warms the soil for these hardy plants, Myers said.

No matter where you live in Oregon, “some of the worst problems we have in the winter are due to the rain, not the temperatures, so protecting the plants from the rain is pretty helpful,” Myers said.

He recommends covering vegetables with high or low tunnels made of metal hoops and clear plastic, available from greenhouse suppliers. You can also use row covers or cloches to protect plants. To warm the soil, use mulch made from garden waste, cardboard or newspapers.

Fingers crossed, and by next March you’ll be able to enjoy peeled, juicy fava beans seasoned with salt and lemon juice.

For more information on extending the gardening season, see the OSU Extension guides “Growing Fall and Winter Vegetables in the Pacific Northwest,” “How to Build Your Own Raised Bed Cloche,” and “Garlic for the Home Garden.” An interactive map showing first frost dates in Oregon is available on the U.S. Department of Agriculture website.

— OSU Extension Service