Unfortunately, you can’t predict when frost will occur. It could strike before leaf buds emerge, or even after flowers blossom.
Because plants break dormancy by late spring, a frost at that time could cause more damage to trees and shrubs than an early spring frost.
“Dormancy provides natural antifreeze to plants,” says Debbie Miller, senior diagnostician and plant pathologist for the Davey Institute. “Once dormancy ends and that internal chemical change within plants occurs, a hard frost, in particular, could cause some major damage.”
When the temperature dips particularly low, a tree’s cambium tissue—the layer beneath the bark, where growth occurs—may suffer and cause more significant damage to the specimen overall. “If the tree is healthy, it will seal the wound,” Miller says. “But if the tree is not that healthy, the wound may elongate and cause bark to fall off.”
Although frost may also prevent some leaves from expanding completely, it may cause other leaves to emerge with holes or distortions. Ornamental trees’ leaf buds are particularly susceptible to frost damage. Loss of flower buds for a season is not as crucial on ornamentals compared to fruit trees.
If your area experiences a hard frost in late spring, don’t attempt to remedy the situation for at least two weeks. “Some plants have secondary buds that emerge later,” Miller explains, “so, if you prune damaged branches too early, you might prevent further growth from occurring.”
You can help prevent frost damage. Most importantly, research your USDA Plant Hardiness Zone and the trees most compatible with your region’s climate conditions before planting new trees. This will help ensure your trees can withstand the weather patterns you may expect to experience throughout the year. For example, it’s not likely a Japanese maple tree can withstand the winter season of northern U.S. regions.
Drought-stressed plants often lack the ability to withstand frost damage, so keep your trees and shrubs well-watered during the growing season, especially evergreens in late fall, to prevent damage in future seasons. Also, fertilize particularly young trees in spring to help them withstand frosts that may occur as they establish their roots and continue growing.