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Despite a warm start to the winter, horticulturists aren't concerned about the state's plants

Colorful pink, white, and purple flowers grow in the center of a footpath. A lawn stretches off to the right and behind them are mostly tall evergreen trees.
Larry Jacobsen
Flickr via CC BY 2.0

This year's winter got off to a warm and dry start. In response, grass remained green and some bushes and trees started to bud out again, which can make them vulnerable when cold weather hits. However, it's still been cooling down in the evenings, which, according to Isaiah Smith, the exterior horticulturist at Cheyenne Botanic Gardens, could help mitigate the major effects.

"We've not had warm days [and] warm nights - you know, an extended summer. We have had that slow progression toward the cool winter," said Smith. "And actually, it is very common for this area to warm up again like that constantly throughout the winter - below 30 [degree] days, and then above 30 [degree] days back and forth."

And according to Smith, most plants have some dieback from the winter anyway, so once there are sustained cold temperatures, it might not be any more detrimental than usual.

"It is slightly detrimental to the plant [if] it froze again, and so that new leaf will freeze and cause damage to the plant, but it's very rarely a large loss. You'll see that new leaf dieback, there'll be some dieback of the plant itself but usually no more than six inches or so. Which is actually common just for the winter anyway -- it's very harsh here, the wind dries things out, and that will cause die back as well," Smith said. "If it'd gone on longer that will be when we're seeing more and more issues with it."

Smith said most plants that do dieback will benefit from trimming off the dead parts and should recover by the end of the summer.

Many perennial plants actually require a certain number of cold days so they can sprout again in the winter, but Smith isn't concerned that they will hit that number.

"Even with some early budding out we still have a long enough winter that we normally will hit our chilling hours more often than not, even double our chilling hours, which is great," he said.

Smith added that the bigger concern is a warm spring.

"They're starting to bud back out again, and we will always have a late frost or a late freeze, or usually, here in Cheyenne, a really late heavy snow. Having leaves on the plant increases the surface area of the branch, which can make some more snow hang on the branch. That's when we get more of our limb breakage, tree damaged as well," he said. "And then for cases such as apple trees, cherry trees, these beautiful spring flowering ornamental trees, that will actually knock off their blossoms. So we get a really short show. And then if it's a fruiting variety of those, we actually will then not have fruit for the year because the blossoms were knocked off before they are fully pollinated."

But, regardless of the winter temperatures, Smith said it's important to keep your plants, especially young ones, watered over the winter. That will help them be more resilient and ready to grow in the spring.

"Snow is moisture, but it's not nearly the same level as rain. There's so little water content in snow compared to rain. So we do need to be watering on top of our snow, as well, as we get it," he said.

Smith recommends watering when the temperature is above 45 degrees and watering slowly and early enough in the day that it will soak in without freezing when temperatures drop in the evening. A good rule of thumb for trees is 10 gallons of water per inch of diameter and five to ten gallons of water a week for shrubs. Most other perennial plants, including lawns, shouldn't need additional watering.

Ivy started as a science news intern in the summer of 2019 and has been hooked on broadcast ever since. Her internship was supported by the Wyoming EPSCoR Summer Science Journalism Internship program. In the spring of 2020, she virtually graduated from the University of Wyoming with a B.S. in biology with minors in journalism and business. When she’s not writing for WPR, she enjoys baking, reading, playing with her dog, and caring for her many plants.
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