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Facing The Chinook!
by Lesley Reynolds
by Lesley Reynolds

email: lreynolds@saltspring.com

Lesley Reynolds is a freelance garden writer who was born in England and emigrated to Regina as a child. Lesley has always loved plants and the natural environment and has gardened in Saskatchewan and Alberta for over 20 years, spending most of that time in Calgary. For the past seven years, Lesley has been working with her friend and writing partner Liesbeth Leatherbarrow and they have several best-selling gardening books to their credit.

In August 2001, Lesley moved with her family to Salt Spring Island, British Columbia. She is enjoying learning how to garden on the west coast and is busy planning a brand new garden.


February 10, 2002


Calgary gardeners face the same challenges as our counterparts across the prairies: low precipitation, wind, temperature extremes, and hailstorms. But those of us who garden in the shadow of the Rockies are also subject to a weather phenomenon that both delights and frustrates. The chinooks that blow from the mountains begin when an Alaskan low pressure area draws warm, moist Pacific air over the mountains. Forced upward, the air loses moisture. The warm, dry air that descends the eastern slopes can produce astounding temperature changes: at Pincher Creek in 1962, the temperature rose from -19°C to +3°C in an hour, an increase of 22 degrees!
We greet the bright chinook arch over the Rockies with mixed feelings. It is undeniably wonderful when a chinook transforms January into May, when streets turn to slush, and people emerge from winter hibernation in shorts. But wild temperature fluctuations are not kind to our gardens. Snow-eating chinook winds suck moisture from the soil and dessicate exposed plants. Snowfall is often sparse, and our plants are more often than not denied its insulating and moisture-retaining benefits. Efforts to "snow-farm" are often all for nought since there is too little snow to redistribute where it is needed.
Prolonged chinooks can also cause plants to break dormancy—often with catastrophic results when the bitter winter cold inevitably returns. Confused non-native plants that just don't know any better are particularly vulnerable. Victoria gardeners may welcome February daffodils, but when they emerge that early in Calgary (it does happen) we can only pile on the mulch and hope for the best.
Once summer arrives, Calgary's altitude of 1000 m above sea level means cooler nights and a shorter growing season than elsewhere on the southern prairies. Even though Calgary averages 112 frost-free days, heat unit accumulation in May and September is low, decreasing the effective length of the growing season to approximately June, July, and August. Late spring blizzards are not unusual. In 1992 it snowed on August 22, much to the disgust of local gardeners, who only a few days previously had been sweltering in +30°C. To add insult to injury, Calgary is also located on the edge of a "hailstorm alley," that averages more than five days a year with hailstorms. 
Did I mention soil? Like other areas on the prairies, most Calgary soil is alkaline, and clay-based as well, requiring the addition of huge quantities of organic matter. Our water is also alkaline; for this reason Calgarians are advised never to add lime to their gardens, even though gardening books from other places may recommend it.
Despite the challenges, Calgary gardeners are a persistent and resilient lot and have created some of the most beautiful gardens in the country through trial and error, and by sharing success stories and tips. What makes for success under such adverse conditions? Some persistent themes emerge: plant selection, microclimates, soil amendment, and winter and summer mulches. We rely on trees, shrubs, and perennials hardy to zone 3. Hundreds of perennials thrive with a little care given to their needs and location. Alpine plants are well suited to the short growing season and there are many splendid rock gardens in Calgary. Drought-tolerant native plants are also finding their way into our landscapes, particularly on acreages with limited water supplies. Surprisingly, there are also many lush woodland gardens, and zone 5 perennials are not uncommon.
The key to limiting winter chinook damage to shrubs and perennials is the application of a 10-cm (4-in.) layer of organic mulch around plants after the ground has started to freeze. Evergreen perennials should be completely covered to prevent dessication. Trees, shrubs, and perennials need to be kept well watered until freeze-up. 
Increasingly, these organic mulches are being left in place on perennial and shrub beds year round. This reduces watering and weeding, while returning valuable organic material to the soil. Some experienced Calgary gardeners leave the soil undisturbed once beds are planted, simply topping up the mulch each year as needed. 
Hardy bulbs and frost-tolerant annuals (snapdragons, sweet alyssum, and pansies) extend our brief growing season. Containers are adaptable to any garden and have the benefit of portability—they can be whisked indoors when a particularly late (or early) frost threatens. 
A large, permanent cold frame is used by those serious about growing warm-season vegetables such as tomatoes, peppers, or cucumbers. These plants, along with corn, dislike the cool Calgary nights, and should be provided with the warmest location possible. Use plastic cloches, tunnels, and row covers when planting early vegetables.
Calgary has a multiplicity of microclimates. Weather can vary dramatically from one part of the city to another. Older neighbourhoods with mature trees have more clement conditions than newer subdivisions perched on hills, or on the windswept prairie around the outskirts of the city. Within individual gardens, buildings, sheltering fences, trellises, trees, shrubs, and vines create warmer microclimates.
Strange as it seems, this dire climate also has some advantages. The dry climate limits the number of nasty pests ready to feast on our gardens, and also allows us to plant fairly densely without increasing the risk of fungus, rot, or mildew. Calgary's cool night temperatures make mid-summer bloom burnout a rarity. Most plants appear fresh throughout the summer, producing brighter flowers and sweeter vegetables than in warmer climates.
Like other prairie gardeners, Calgarians rejoice in their successes and shrug philosophically at the inevitable casualties. After all, there's always next year, and while winter chinooks blow, there's plenty of time to dream, scheme, and plan that perfect garden.

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