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September 11, 2019

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Understanding Hardiness Zones

Gardening can be a challenge in any climate, but in the western provinces, we seem to get so many variables that some days one might wonder why we bother. Taking a look at this season’s many successful flower pots, vegetable plots and tree lots may explain why because when all factors work in our favour, we can grow some pretty spectacular gardens in Alberta! When it comes to deciding what to grow, knowing what hardiness zone you are in is a good place to start, followed by joining a local garden club, touring a regional botanical garden and some good old trial and error.

“A hardiness zone is a geographical area defined to encompass a certain range of climatic conditions relevant to plant growth and survival” –Wikipedia

Want to compare zones throughout Canada? Check out Canada’s Plant Hardiness map, www.planthardiness.gc.ca, which shows the various zonal areas throughout our country. Zoom in to Alberta to see the variables that are in our own province, from zone 0a to 4b. In 1967, Agriculture Canada scientists created a plant hardiness map using Canadian plant survival data and climatic variables, including minimum and maximum temperatures, frost-free periods, and wind and moisture levels throughout the year. (USDA created one earlier using only minimum temperatures.)

Since the origin of the Hardiness Zone Map, our plant hardiness was categorized as Zone 3; that is, until 2014 when another update using the same variables, but with more recent climate data and newer mapping techniques, we were upgraded to Zone 4a. In a nutshell, we can grow plants that are hardy to zone 4a and lower. If you want confidence that your plants will survive, stick with zone 3 or lower; but know that there is a whole bunch of plants that we can now add to our growing list. If you’ve recently purchased a bunch of zone 4 plants (as we have a great selection) and feel you might be pushing the boundary of our gardening limits, plant them in protected spaces of your garden, mulch and keep them well watered and fed.

Choosing plants that are hardy to our growing zone is just the beginning of ensuring survival in our prairie and chinook zone gardens. Choosing the right plant for the right place, providing appropriate soil, sunlight, moisture and ongoing care and maintenance of plants are also factors in growing success. Some seasons we will suffer variable weather conditions such as too much rain, hail, drought, early snowfalls, extreme freezes and chinook winds; these will also impact how your plants survive. As gardeners, we will also survive the challenges to a hobby that many of us love, as the rewards are in the doing and in the results.

Zoned in or zoned out, we are only limited by the challenges we put in front of ourselves as gardeners. Enjoy the journey, the rewards and getting your hands dirty!

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