Recent cold weather won’t harm your plants, but take precautions if chill worsens

Gardeners who’ve seen flowers emerge early because of the warm weather needn’t be overly worried about the recent drop in temperatures.

Experts say most plants can handle temperatures above 30 degrees. But steeper drops in temperature, such as cold snaps in the 20-degree range, remain a possibility.

Christine Rollinson, an expert on forest ecology at the Morton Arboretum, said some plants had leaves or flowers emerge weeks to a month early this year. But other plants are still “on the very, very first flower,” she said.

“Come out early, you get a longer growing season. But the earlier you come out, the higher the chance that you're going to be hit by a deep freeze,” Rollinson said.

With warmer weather, plants using temperature cues got a “head start” in their development, according to Rollinson. But other plants rely on additional cues, including intrinsic molecular clocks, to wait longer.

“There are a whole bunch of other plants out there that know that the weather can be weird,” Rollinson said.

This week’s weather has stayed in the 30s, but Rollinson said she wouldn’t be surprised if the Chicago area gets a “blast of cold air" in the coming weeks.

Over a 30-year period, most Aprils have experienced one or a few days in the 20-degree range, according to the National Weather Service.

Some plants, such as cauliflower, broccoli and kale, are well-adapted to the cold. But tender plants, which are sensitive to frost, should be looked after in the event of a cold snap, Rollinson said.

“Just be prepared to take care of those plants — to cover them to help keep heat in, if we do get a cold snap,” Rollinson said.

As for trees, there are fewer precautions that plant caretakers can use because trees are hardier and meant to live for a long time, Rollinson said.

“As long as this kind of weather happens once in a while, it'll stress the tree out, but the tree will be OK,” Rollinson said.

Olga Lyandres, a Lake View gardener, plans to start planting in May, when there’s more “pleasant weather.”

By waiting, she can avoid any possibility of a freeze, Lyandres said.

“Sometimes, the weather fluctuations do throw things out of whack and confuse gardeners and plants,” Lyandres said.