Be prepared in the garden in case of a cold snap

mulch
Mulching tender perennials can help protect them during a cold snap. Photo by Hannah O’Leary.
Last Updated: 
February 6, 2015

CORVALLIS, Ore. – Spring seems to have arrived early in western Oregon, but never count on the weather. Though this year is shaping up to be mild rather than wild, anything can happen.

There are still more than two months until April 15, when you can, on average, count on saying goodbye to frost, according to Al Shay, a horticulture professor at Oregon State University.

“Certainly a cold snap down to 20 degrees in March will wreak havoc,” he said. “That kind of cold weather could bring an end to new growth, buds, flowers, or even the whole plant.”

Watch the forecast, Shay advised. If you see the temperature is going to drop below 20 degrees, he recommends the following:

Cover plants you suspect will be damaged with an old sheet, tablecloth, woven row cover or sheet of plastic. Use stakes to prop the material over the plant and weigh down the edges with rocks, bricks or whatever you have on hand. The Willamette Valley is rated Zone 8 on the USDA hardiness scale, which means if you bought plants labeled Zone 8, they’ll be OK down to about 15 degrees.

If you don’t know the hardiness of your plants but have lived in the same place for more than a couple of years, think back to which plants limped through winter and concentrate on those. Be sure to remove the material when the temperature rises.

Pull potted plants into an unheated garage, basement, greenhouse, cold frame or similar site. Make sure it's a place where the temperature stays above freezing. If you’ve no place indoors for plants, safeguard them by covering with evergreen boughs, straw or leaves. Securing a piece of bubble wrap or burlap around the pots also helps. Be quick to remove it once the weather warms.

Provide mulch for tender perennials – including hardy fuchsias, roses, clematis, salvia, some ferns, canna, agapanthus and dahlias – that are still in the ground. For extra protection on plants you particularly prize, use this trick: Assemble a tomato cage (the square, folding types are best) around it. Wrap burlap around the outside of the cage and secure with bungee cords. Fill with straw or leaves.

Shake heavy snow off shrubs and trees to keep branches from breaking or bending. Leave snow at the base of plants, however, because it insulates roots.

Remember to water. Even if it’s cold, plants need to be watered if they dry out. Pay special attention to those under eaves or large trees that don’t allow rain through.

Stalk slugs, which are already sliming their way through the garden. Trapping or putting out bait now would be the ticket to keep them from taking over. Also, watch for other insects you’ve had trouble with in the past. If you catch them early, it’s possible to use less-toxic controls such as horticultural oils and soaps.

Sit tight. Don’t start planting or fertilizing just yet. Use a thermometer to check the soil temperature and wait until it reaches at least 50 degrees before planting cool-weather crops such as peas, greens, radishes, cabbage and broccoli, and 70 degrees for warm-weather plants such as tomatoes, peppers, eggplants and squash.

Author: Kym Pokorny
Source: Chrissy Lucas