USDA Zones In Canada: Are Canada Growing Zones Similar To U.S.

Hardiness zones provide helpful information for gardeners with short growing seasons or extreme winters, and that includes much of Canada. Without Canadian hardiness maps, it becomes difficult to know what plants are tough enough to survive winters in your particular area.

The good news is that a surprising number of plants can tolerate Canada growing zones, even in the northern part of the country. However, many can’t survive outside of their designated zone. Read on to learn more about hardiness zones in Canada.

Hardiness Zones in Canada

The United States Department of Agriculture (USDA) released the first hardiness zone map for North America in 1960. Although the map was a good start, it was limited and included only minimum winter temperatures. The map has become much more sophisticated since that time.

A Canadian hardiness map was developed by Canadian scientists in 1967. Like the USDA map, the Canadian map has continued to evolve, with the last Canada growing zones map released in 2012.

The current Canadian hardiness map considers several variables such as maximum temperatures, maximum wind speed, summer rainfall, winter snow cover, and other data. Hardiness zones in Canada, like the USDA map, are further divided into subzones such as 2a and 2b, or 6a and 6b, which makes the information even more precise.

Understanding Canada Growing Zones

Growing zones in Canada are divided into nine zones ranging from 0, where weather is extremely harsh, to zone 8 which comprises certain areas along the west coast of British Columbia.

Although the zones are as precise as possible, it’s important to consider microclimates that may occur in each area, even in your own garden. Although the difference is small, it can make the difference between success or failure of a single plant or an entire garden. Factors that contribute to microclimates may be nearby bodies of water, presence of concrete, asphalt, or brick, slopes, soil type, vegetation, or structures.

USDA Zones in Canada

Using USDA zones in Canada can be fairly complex, but as a general rule of thumb gardeners can simply add one zone to the designated USDA zone. For example, USDA zone 4 is roughly comparable to zone 5 in Canada.

This easy method isn’t scientific, so if you’re in doubt, never push the limits of your planting zone. Planting in one zone higher provides a buffer zone that can prevent a lot of heartache and expense.

Mary H. Dyer

A Credentialed Garden Writer, Mary H. Dyer was with Gardening Know How in the very beginning, publishing articles as early as 2007.