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Warm Winter's Effect on Plants

Feb 1, 2012; 11:09 AM ET

This article is written by Doreen G. Howard, long-time contributor to The Old Farmer's Almanac.

Buried under 25 feet of snow, coastal Alaska gobbled up the winter cold and snow we normally have in the northern tier of the country. Chalk it up to the Arctic Oscillation, a rare phenomenon that is killing my perennials and shrubs.

When the ground remains warm, as it has during this strange winter, and is suddenly covered by a heavy snow pack and sub-zero temperatures, plant roots suffer. Many die, especially when the thaw-freeze pattern is repeated.

We've had no snow this season until Jan. 12, when a blizzard dropped 8 inches and temperatures plunged below zero. Jan. 11, it was 59F and sunny, as it's been most of the winter. Daffodils had been popping up in the previous weeks.

I planted a plethora of Echinacea last summer, thinking I'd have colorful workhorses in my perennial beds that would also draw pollinators and feed birds during the winter. Dan Heims,accomplished breeder and president of Terra Nova Nurseries, explained to me that in order for Echinacea to succeed in cold climates like mine (USDA Zone 4b), I had to deadhead ruthlessly the first year in the ground. I shouldn't let plants blooms, but pinch off the buds as soon as I spotted them. Plants then spend their energy building extensive root systems to survive in the cold. I hope it worked!

Learn more about caring for coneflowers (Echinacea) here.

I planted 26 different coneflowers last spring, including Pow Wow, with great hopes of a colorful display throughout the growing season. Photo courtesy of Ball Horticulture Co.

I also left dead chrysanthemum and aster foliage on plants. According to the Univ. of Iowa, the foliage blanket insulates plant roots. But.....it may have insulated them too well, and below zero temperatures probably damaged roots in warm soil.

And, I worry about shallow-rooted shrubs like blueberries. Hopefully, the foot of pine straw I mulched them with will keep root-kill to a minimum.

Rose canes are still green with intact leaves in mid-January due to the warm winter. With the sudden onslaught of snow and sub-zero temperatures, roots will probably die in the warm ground. The chrysanthemums won't make it either.

Roses are toast. Most canes were green and buds are plump when the storm hit. They'll probably die and only the rootstock upon which they're grafted will survive. Those on their own roots, like Therese Bugnet, may survive. We'll see.

Learn more about caring for roses here, or continue reading about gardening on Almanac.com here.

Doreen G. Howard

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