The Cold Garden Micro-climates

We all know that within an area, growing conditions can vary quite a bit due to micro-climates. However, what is a desirable micro-climate in a temperate area, might not be desirable in a place with cold winters like Canada or much of the northern United States.

What grows best in a protected spot is different in cold and in temperate climates

Gardeners in mild climates vaunt the virtues of a warm spot at the base of a south-facing wall, especially if it is protected from wind. Such a spot will warm up faster in spring and provide better growing conditions than a place more exposed to the elements in the same garden.

However in a cold climate garden, such a spot is often not desirable for perennials.  In such a protected place, growth usually starts too soon in the spring, and the risk of frost damage is much higher than in less protected spots where growth will be delayed.

In our cold climate, you will want to site your hellebores in a place where they won't bloom too early

In cold gardens, the desirable spot  is one where snow tends to accumulate over the winter. In such a place growth begins later in the spring, only after most of the snow has melted. By the time that snow-covered plant does start to sprout, all dangers of frost are usually over.

Snow is welcome in cold gardens as it provides insulation from bitter cold. The most desirable thing for a cold climate gardener is a reliable snow cover that comes in December and does not leave till March. Under a foot of snow, temperatures at ground level will hover around the freezing point, even if it is -20 or colder above the snow.

What kills plants in our cold climate is a warm spell that melts the snow, followed by a sudden hard frost. In areas of the garden where snow tends not to melt easily, plants are protected from severe temperature fluctuations.

For us, wisteria is border-line hardy, you will want a western exposure to ensure flower buds develop as late as possible

Large bodies of water also make a big difference. Roche Fleurie is on a narrow stretch of land between Lake Huron and Georgian Bay. In the autumn it takes a long time for all this water to get cold, so autumns tend to be warmer than 100 miles south where there is no lake effect.

But in winter, all this water freezes and consequently the air tend to stay cooler for a longer time in spring, because we are surrounded by ice. Spring is earlier 100 miles south.

The proximity of large bodies of water tends also to produce evening fogs which help a lot with moisture

Exposure also produces different results in warm and cold gardens. In a warmer climate, for a southern exposure, you will select plants that can take a lot of heat such as zinnias. In a garden where summers are cool, too hot is not as much of a concern. There the selection of plants for a hot southern exposure will be wider because that southern exposure likely won’t produce too much heat anyhow.

Finally, favorable microclimates in cold weather gardens make a bigger difference for perennials than they do for trees and shrubs.  Let us say you are in a zone 5 (where temperatures can go down to -10, -20 F) and for a couple of nights temperatures go down to -25F.  Even grown in a favorable microclimate, your Japanese maple might not make it, but your zone 5 perennials will have a better chance of surviving ( in fact they are unlikely to suffer at all if they are covered by snow).