‘Tonight’s the night’: Protect your plants, Boise. Temperatures to drop below freezing
For just the eighth time in May since records began in 1892, Boiseans woke up on Monday morning to over one-tenth of an inch of snow covering trees, cars and rooftops. By the time the snowstorms had passed through the Treasure Valley mid-Monday morning, half an inch of snow had fallen at the Boise Airport.
Around 2-3 inches of snow was reported around the Boise Foothills, NWS meteorologist Spencer Tangen told the Idaho Statesman, while Bogus Basin recorded at least a foot of snow.
Even though the snow transitioned to rain throughout the latter half of Monday, Boise hasn’t seen the last of wintry weather. The NWS issued a freeze warning from 3 a.m. to 9 a.m. Tuesday morning for the majority of the Treasure Valley and western Magic Valley.
Temperatures will drop to around 30 degrees throughout the Treasure Valley and 28 degrees in the Magic Valley in the early hours of Tuesday morning.
The average last winter freeze for the Boise Airport, since the NWS began keeping track of that data in 1940, is May 5th, but this is just the fourth time in the previous 10 years that temperatures have hit freezing in May or later.
NWS meteorologist Bill Wojcik told the Statesman that a freeze warning is often sent out not because of dangerous road conditions but for frost-sensitive plants and vegetation.
“It’s mainly to give people a heads up if they’ve planted frost-sensitive vegetation,” Wojcik said. “Just to take care and be preventative. If you want to protect them, tonight’s the night to do it.”
How can you protect your plants?
Garnette Edwards, owner of Edwards Greenhouse in Boise, said that owners of annual plants and vegetation should be cautious about their greenery while owners of perennial plants don’t need to be as concerned. Annual plants typically only live for one season, while perennial plants grow for at least two years and often much longer.
“Items like sweet potato vine, or impatiens, or begonias, those items actually freeze at a higher temperature,” Edwards said. “It’s somewhere between 36 and 33 (degrees) that some of that stuff can be really damaged”
Other flowers such as geraniums and petunias can tolerate cold temperatures down to 29 degrees, Edwards said, so they should be fine but may require a close eye. She also noted that vegetables such as peppers, tomatoes and cucumbers would require special attention.
For overnight protection, Edwards said plant owners should cover their plants with either a regular bed sheet, blankets or a floating row cover. If possible, she recommends putting plants in a pot and pushing them up against the side of your house and covering them due to the outside walls of the house providing some warmth and shelter from wind chill.
“You do not want to cover (plants) with plastic,” Edwards said. “Because it can build up the heat as the sun comes out underneath it, damage the foliage, and be just as detrimental as the frost.”
Franz Witte garden center in Nampa posted a tip sheet on its Instagram page Monday morning, recommending plant owners cover anything with growth with bed sheets and blankets. The post also recommends pruning off any broken branches on trees and shrubs and to avoid leaving sharp and jagged branch edges to freeze over.
How can you rehab your plants?
Once temperatures rise above freezing in the morning, Edwards recommends sprinkling any outdoor plants with water to help warm them up more quickly.
For any plant that does seem to have suffered frost damage, she said to wait up to ten days to see if growth continues. If it does not, she said that many nurseries and greenhouses in the Treasure Valley, including her own, continue to stock annuals until the 15th of June or later because of the potential for freezes.
“I wouldn’t rush out for a day or two and plant everything up,” Edwards said. “Just because it’s warming up, you want the ground to warm up a little bit too, or that’ll set your plant material back.”
This story was originally published May 9, 2022 at 4:23 PM.
