Do revisions to Canada's plant zones map mean changes to our landscape?
A few years ago, Jennifer Jones (Landscape Architectural Technology ’05) planted Japanese blood grass at her home in St. Albert, northwest of Edmonton. It’s a striking specimen, maturing to a graceful stand of green blades tipped with crimson.
The NAIT Landscape Architectural Technology instructor put it in as an accent plant for the season, not expecting it to survive the harsh Prairie winter. Japanese blood grass (pictured above), after all, isn’t rated for Edmonton’s gardening zone, 4a, which is defined by factors including temperature and precipitation.
In fact, it’s more at home in locations stretching from southern Texas to South Dakota (with scattered pockets in Washington and Montana). Nonetheless, it sprouted the next spring.
“I remember thinking it was an annual and then being surprised that it kept coming back,” says Jones. It’s still growing today – a testament to how a changing local climate is improving what Jones calls “a limited planting palette” in the Edmonton area.
What does that mean to the average gardener? With the help of Jones and CTV Edmonton meteorologist Josh Classen (Radio and Television – TV ’96), we dug into the issue of Canada’s shifting plant zones.
Why more plants can survive in Edmonton
Jones, like many people of a certain age, has an odd nostalgia for the brutal cold snaps and mountainous snowdrifts of the winters gone by. The season no longer seems so hard to take. Is that just a trick of memory?
Not according to Classen (left). Knowing that, over the past 30 years, Natural Resources Canada has bumped up Edmonton from zone 3b – reflecting a milder local climate – the meteorologist crunched numbers on local conditions.
“I’m surprised at how much of a jump there is in temperature, especially over the winter,” says the 2017 recipient of NAIT’s Alumni Award of Excellence.
Classen found that the overall January average in the city is up roughly 4 C compared to the 1960s, ’70s and ’80s; February and March are up 3 C. “The temperatures are up and they’re way up. Your morning lows are not as cold as they used to be and your daytime highs are warmer.”
“The temperatures are up and they’re way up."
While he doesn’t make light of the negative impact similar increases have elsewhere in the world, Classen sees how the local effect may seem positive.
With a plant’s hardiness – or likelihood of surviving the winter – being a factor of the low temperatures it can endure, milder winters will inevitably alter, and perhaps aesthetically improve, city landscapes.
“I’m a horrible gardener, but I love gardening,” says Classen. The warming weather will help. “There are a lot more plants that you can grow in Edmonton than you might have thought.”
Landscaping tips for Edmonton’s gardening zone
Jones (right) has noticed how Edmonton-area garden centres now sell more plant material representing a wider variety of zones. “You have access to a lot more interesting foliage colours, different bloom times, different flowers, even.”
While retailers have embraced the region’s new zone rating, stocking plenty of zone 4, sometimes even zone 5, plants, Jones still recommends tougher, reliable material for large, exposed landscaping projects. In such cases, she’d pick plants suited to as cold as zone 2 (Fort McMurray).
The local backyard is different. “In a smaller, residential setting you have the opportunity for a lot of trial and error,” she says. Gardeners can leverage balmy microclimates created by nearby concrete pads or building facades – they can take a chance, for example, on Japanese blood grass.
"You can really push the limits of zoning.”
“At that scale, you can really push the limits of zoning.” Here’s how she recommends to do that in a northern Canadian city, regardless of long-term trends and forecasts:
- Don’t use higher-zoned plants as the backbone of your landscape design. Instead, treat them as accents that can be easily replaced if necessary. “If there’s a rough year, you never know if you’re going to lose that plant,” says Jones.
- Come spring, be patient. More sensitive plants may take longer to sprout and may grow more slowly than tougher ones. Jones’s blood grass tends to be the last plant in the garden to leaf out.
- Plant higher-zoned plants early in the season. Usually, Jones recommends to “shop in the fall to get the discounts." While tougher plants have little trouble surviving despite late planting, she likes to give potentially tender varieties more time to put down roots before colder weather arrives.
- Insulate sensitive plants over the winter by covering them with snow – that is, if these kinder, gentler winters produce enough of it.