Hardiness zones are important for all to know.

Gardening is the fastest growing leisure activity in North America. Every year both young and old discover it. The joys and rewards of gardening include the practical, such as growing herbs and vegetables for consumption, to the exotic, such as breeding orchids or cultivating special hybrid roses. Gardening can be fulfilling both spiritually and physically.

Choosing plants for our landscape and gardens can be sometimes be as challenging as growing them. All plants have specific climatic and care considerations.  For instance, one of my favourite herbs is rosmarinus or rosemary. It is native to the warm coastal areas of the Mediterranean and therefore considered semi-tropical. I live near London, ON, in Hardiness Zone 6 and the only way I can grow rosemary is in a pot. I put it outside during the summer but I have to bring it in at the first signs of a frost in the fall. However, in southern Arizona (Zone 9 & 10+) rosemary grows profusely in gardens and landscapes.

What is a Hardiness Zone? A hardiness zone is where types of trees, shrubs and flowers will most likely survive and is a specific geographical area with its own set of environmental conditions. These zones are based on the average climatic conditions of that area. A hardiness zone map is a graphic representation of a number of zones. These maps are usually found in the front pages of gardening books, seed catalogs and can be obtained on the internet from your federal department of agriculture.

Canadian Plant Hardiness Zones

Both Canada and the United States have their own hardiness zone maps, which unfortunately are slightly different. The American hardiness zones were recently revised. For Canada, a plant hardiness map was created using Canadian plant survival data and a wider range of climatic variables such as minimum winter temperatures, length of the frost-free period, summer rainfall, maximum temperatures, snow cover and even January rainfall and maximum wind speed. The harshest zone (0) is the Arctic and northern part of Canada and the mildest is parts of Vancouver Island having Zones 8 & 9.

Knowing and understanding hardiness zones is important. This information will come in handy when you are purchasing new perennials or shrubbery and will take some of the guesswork out of your plant choices. Gardening is an endless trial and error process but knowing your zone will help ensure your purchases have a better chance of success.


More about other factors that impact growing success

Nancy Abra, London Middlesex Master Gardeners