When you think of a Canadian winter, you think of the frosty temperatures and snow. But oddly enough, cold and, in many cases, even snow, aren't your garden's worst winter enemies; it's the wind and those sunny winter days we love that could kill our plants.
"Wind can be the real villain, especially with roses," says Tim Schwenker, head gardener of Hendrie Park's ornamental plantings at the Royal Botanical Gardens in Hamilton, Ontario. "People wonder, ‘Winter wasn't that bad, but my rose canes all died to the ground.'"
Cold winter winds, explains Schwenker, dry out the branches of roses and other exposed shrubs. Gardeners are often prepared to deal with the cold, but forget the blasts that slam into their gardens from the north and west.
Wind can even damage the roots of top-heavy plants like hybrid tea roses and newly planted trees and shrubs. When it comes to these new plants, there's one stem and many branches but no major root system, especially if they weren't planted right in the first place, says Schwenker. It's tough for a plant to make a comeback from that kind of winter beating.
Sun: nice for us, not for our plants
A newly planted garden in direct winter sun can be at real risk. "The worst thing for plants, particularly perennials, is alternate freezing and thawing," says Schwenker. Plants will sustain root damage from heaving and also from the standing water left behind after the snow melts.
Some trees, too, suffer from the winter sun's rays. Apples, flowering crabapples, black cherries, some maples and ornamental cherries—especially grafted ones like the ‘Kwanzan' Japanese cherry—are the most vulnerable: One side of the tree heats up, and the frozen wood expands, then splits. To a sensitive gardener, unsightly frost cracks running down the trunk are heartbreaking. The wound will heal itself eventually, Schwenker says, but repeated over the years, the weakened tree could fall over.