Recent Cold Weather Will Test Plant Hardiness

This sudden recent cold weather has me worried about plants which I planted this year. Are we likely to have a lot of winter damage to plants this year?

Answer: The most recent cold snap will test the hardiness of a lot of plants. Because of warm fall weather, many plants were not completely dormant when temperatures dropped into the single digits.

Look for plant damage when plants begin to grow next spring. The plants most likely to suffer damage are those planted in late summer or early fall. They may not have had time to establish a sufficient root system.

Another group is perennial plants including trees and shrubs planted in containers. They should be moved to a protected location such as a covered patio, garage or shed by mid November.

A few years ago we had temperatures down into the teens in December which damaged several broad leaf evergreen plants which are commonly planted in the Pacific Northwest. These were Escalonia, Viburnum Spring Bouquet, and Choisya (Mexican orange). In some cases plants were killed down to the ground. In others, some branches were killed and other branches damaged. I did not see a case where the entire plant was killed. If this occurs this year, simply prune off all the dead wood in the spring after growth starts. In some cases you may need to remove some undamaged tissue in order to shape plants. In most cases, plants will regrow near to their normal size in a single season.

I checked both USDA and Sunset hardiness zone ratings for all three of these plants. They are all rated as hardy in the main metro areas in western Washington and Oregon. However, Sunset cautions that damage can occur below 15 degrees on two of them.


Allen Wilson

Allen has been writing about gardening for over 30 years. He is a retired professor of Horticulture.

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