Celebrating Our Zone

Okay, let me be the first one to say it. I love gardening in Calgary. Not kind of tolerate, not passively enjoy, I absolutely love growing plants in our unique climate. The mild and moist conditions found in British Columbia are terrific, as is the hot and humid climate of Southwest Ontario and environs, but I am taking a stand and telling every person who has garnered a hoe this side of the Rockies: don’t look any further – it doesn’t get any better than right here in your own back yard.

What’s so special about Calgary? In horticultural discussions, I often hear fellow gardeners lamenting the “difficult” growing conditions found in the greater Calgary area. Along with (admittedly) challenging soil composition, gardeners wax poetic on issues of long and cold winters, variable Chinooks, cool summer nights, insufficient rainfall, and cool zone rating. So focused are we in finding fault with our special growing conditions, in fact, that we often overlook the upside of gardening here: nestled with one leg in the prairies and the other in the foothills, Calgary’s interesting location and localized climate present a prime opportunity for growing fabulous gardens.

Sunny Sunny Days
Reminiscent of the old Wink Martindale song, Calgary is one of the sunniest cities in North America. Averaging 2395 hours of sunlight per year, the sheer volume of energy bathing our gardens during the growing season promotes healthy, happy plants. Native varieties such as chokecherries, saskatoons, poplar, buffaloberry, willow, and certain roses are able to capitalize on our long days during the growing period by maturing quickly and, where applicable, producing heavily for entire months at a time.

Cool Nights
Even the hottest of Calgary summer days experiences a substantial cooling overnight. This cooling period is actually a blessing in disguise for most garden varieties as it helps to keep harmful pests and diseases at bay by inhibiting reproduction, keeps lush overgrowth in check, increases sugar content in fruit crops, and intensifies pigmentation in flower blooms. Few are the gardens that can boast the tasty berries and stunning colors that we commonly feature in Calgary.

Winter Wonderland
Yes, we do enjoy (ahem) a long dormancy period in Calgary which often eclipses over 6 months of the year. But even this extended slumber offers benefits to our gardens. With a relatively short very cold period (i.e. -20°C to -35°C, usually timed sporadically from November through January), hardy plants in our gardens are able to take advantage of the extended cool period (i.e. 5°C to -15°C, usually timed from October through early November and again from February through March) to enter and exit dormancy. Plants that need long periods to harden off for winter thrive here; ash, elm, and oak are prime examples of elegant, long-lived trees lining the streets in Calgary. Also favorable to the classic cold snaps we see in the winter months, most garden pest populations (caterpillars, aphids, and mosquitoes, to name a few) are severely depleted when temperatures drop below -30°C. Calgary gardens tend to emerge in the spring fresh from pests, very healthy, and ready to grow!

When it comes to gardening, Calgary seems to have the best of both worlds. Our somewhat unusual climate is mild enough to produce some of North America’s most stunning gardens and yet harsh enough to do some of our gardening dirty work for us, such as regulating substantial pest over-populations. Along with the various challenges that growing in the Chinook zone presents, we should also take time to capitalize on our unique opportunities for creating fabulous, long-lived gardens. As the old adage goes, we can lament roses because they have thorns or we can rejoice thorns because they have roses!

Gardening in the Zone
With an average rainfall of 203.3mm and a minimum winter temperature of –34.5 to –37.2°C, the USDA (United States Department of Agriculture) has roughly set the Plant Hardiness Zone Rating for Calgary as 3a (hardiness zones are set from 0 – 8, with 0 being the harshest and 8 being the mildest.) Agriculture Canada has modified this rating to 3b with the inclusion of such factors as elevation, maximum wind speed, length of frost free days, amount of typical snow cover, and January rainfall. Given the micro-climates found in most yards in Calgary, a substantial number of Calgary homes also possess a pocket or two of relatively protected space that would adhere to a Zone 4a or 4b rating.