Some like it Cold
Garden Clippings for Feb 5, 2022
Frozen waterlines, weak car batteries, and burst watermains are stuff that winter in Canada is made of. Especially in the last two weeks.
You and I can deal with the cold by putting on an extra layer or bundling up in front of the fireplace, but plants can do nothing to combat the cold. While the human body does its best to maintain a temperature of 36 or 37 degrees C, plants get as cold as the air surrounding them.
For the most part, plants don’t mind the cold. In our temperate climate zone, plants need winter as much as they need summer. If our plants did not endure a cold spell, we would have Palms and Pothos instead of Maples and Pines.
All plants have genetic traits. They can be tall, short, pink, spreading, drought tolerant, big-leaved, or thorned. Another trait is cold hardiness. Plants growing in Southwestern Ontario are suited for our temperature range.
Sometimes we push the limit with plants. Redbud, for example, is a native tree that grows well in Southwestern Ontario, but will struggle north of Owen Sound or east of Kingston. Ditto for Peach trees, Butterfly Bush and Rhododendrons.
Different parts of plants have differences in tolerance for cold. We sometimes assume Japanese Maples are cold sensitive, so gardeners will go through the effort of wrapping them in burlap. But Japanese Maples are tough as the dickens and don’t need a jacket over their bodies. Their roots, however, don’t like the severe cold, an issue compounded by the fact their roots like to grow near the soil surface. The solution is putting down a layer of mulch to provide insulation for roots.
Butterfly Bush are the opposite. After a mild winter, the plant may survive like any other flowering shrub, but here in Lambton County, their shoots and buds will likely freeze and die off, only to have their roots send up new shoots once warm weather arrives.
Growing Peach trees in Lambton County is easy because of our favorable temperatures. All is well when buds begin to swell in April, but if we get a nasty cold snap in May after buds have swelled, Peaches might be doomed.
Rose of Sharon’s leaf buds and stems are vulnerable to severe cold and will sometimes need an extra month in spring to open up. Forsythias, known for their hardiness, can lose their flower buds if exposed to severe cold.
Plants that are covered in snow have no issues with cold because snow is nature’s insulator. Farmers who plant winter wheat sleep well at night as long as a few inches of snow cover the soil and stems. It is when wind is cold without snow cover that they lay awake.
Rhododendrons and other broad-leafed evergreens don’t mind the cold but are not keen on winter wind and sun that pulls moisture out of their leaves. Give these plants a protected spot or cover with a burlap sack.
Like people, the healthier the plant, the better it will withstand cold. If your plants are established, well fed, and have built up moisture reserves, they will manage winter woes with ease.
Finally, acclimatization plays a role in a plant’s ability to withstand severe cold. A marginally hardy plant may suffer damage if hit with a cold snap in December, while the same temperatures in February will do no harm.
