Gardeners and homeowners wondering what the deep freeze of November 2014 will do to their landscapes have had horticultural websites buzzing.

"I think only time will tell on the extent of damage we'll see," said Colorado State University Extension horticulture agent Alison O'Connor, who's based in Fort Collins. Like many, she had roses still blooming as the first flakes fell and the mercury tumbled.

The closest weather-event comparison experts could make was to the Halloween freeze of 1991, which the following year, "proved to be fatal to many shrubs and trees, particularly Siberian elms," O'Connor wrote on CSU Hort Blog

The shock of 14-below temperatures a few days after balmy 70-degree afternoons can be tough not just on humans, but on valuable, expensive-to-replace trees and shrubs, especially if they were newly planted or went into the prolonged cold days without adequate water.

Dave Paricio, a certified arborist with the Davey Tree Experts' east Denver office, was also cutting the last of his own roses as temperatures began to plummet.

"We will see some injury (to trees and shrubs), but nothing's going to be readily apparent until early to mid-spring," he said. But last spring and summer's abundant moisture will help.
Also on the side of the plants: Soil isn't as cold as air. And soil with moisture in it holds heat better than drier soil.

"We will see some root damage" on newly planted trees, Paricio predicted. Air pockets around those not-yet-established root systems can make those roots dry up and contract. If plants went into the freeze well watered and mulched, you can rest assured that you did all you could.

What can you do now?
• For Roses, prune off any blooms if the weight of snow on them is bending canes. Once the plant has dropped its leaves, increase the mulch around the base of the plants to six to eight inches. (Come spring, you'll pull that mulch away so the soil can begin warming up.)

• Mulch other shrubs and trees, remembering to leave a few inches between trunks and mulch (roses are the exception).

• Don't sweep remaining ice-melt into garden beds. Sweep it into a dustpan and dispose of it. Such salts aren't good for plants and over time can build up in soil, according to the Associated Landscape Contractors of Colorado, a trade group.

• Remember to keep shrubs and trees watered through the winter. If you're not sure whether snowmelt has done this winter watering chore for you, see if an old screwdriver penetrates the soil to six to eight inches. If you have to force it, soil is dry. Check every couple of weeks, paying special attention to new plants or plants in conditions exposed to lots of sun or lots of wind. Water the established plants at least monthly, around noon on days when the highs reach above 40 degrees.
"If (you) can do it with deeper watering probe, great, but any water is better than no water," Paricio said.

• If you haven't already, wrap the trunks of young trees to protect them from sunscald. You can buy tree wrap at most hardware or garden stores; wrap from the trunk up. (And don't forget to remove it — Paricio said he times this chore for April 15, right along with Tax Day).

• Schedule a professional pruning for mature trees, especially those that haven't had one in a few years. Certified arborists can tell dead limbs from live ones even in winter, Paricio said.

• You can always hope that 2015 offers growing conditions as kind as those on offer in 2014 — not too hot, not too cold, decent rain.  Right?  "This is Colorado," Paricio laughed. "We can't count on anything."

Susan Clotfelter: 303-954-1078, sclotfelter@denverpost.com or twitter.com/susandigsin

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