Canada’s updated its plant hardiness map — and growers are seeing their options bloom

The Victoria Day long weekend is widely considered the start of the gardening season, and this year, gardeners have new information about which new types of plants might survive outdoors in their area.

“The main reason for that is the climate is changing,” said John Pedlar, research scientist with the Canadian Forest Service.

Pedlar is one of the researchers who recently updated Canada’s “plant hardiness zone map” for the first time in a decade.

It’s a tool used by nurseries and everyday gardeners to determine which plants are most likely to survive in a particular climate. 

The data comes in the form of a map and factors in everything from rainfall to winter temperatures and wind conditions.

The Natural Resources Canada (NRCan) released the updated data in July last year.

Plant hardiness zones are areas that largely have “similar climate conditions,” Pedlar said. They range from a stark 0A, where practically nothing grows, to the lush 9A. 

“Since plant survival and climate are so closely intertwined, it stands to reason those areas also have fairly similar plant composition as well,” he said.

While the biggest changes to the map were in western Canada, places like Almonte in eastern Ontario increased by a full zone.

Other growing areas around communities like Kemptville and Smiths Falls rose by half a zone.

That means gardeners may now be able to grow cherries, pears and even some varieties of apricot that previously wouldn’t have survived, Pedlar said.

Ottawa and Kingston did not change, remaining in Zone 5A.

At Robert Plante Greenhouses in east Ottawa, inventory has had to be updated regularly in order to keep up with the changing climate.

“There are more and more types of plants that you can plant for sure in our area,” said manager Colin Matassa on Sunday.

Matassa said staff are trained to know which plants will work in which zones, but it’s also easy for gardeners to figure it out themselves.

“In all our perennials, shrubs and trees, they all have information tags on them. It’ll say the zone on the back, whether it’s Zone 5, Zone 4 or Zone 3,” he said.

The May long weekend, Matassa said, is typically the greenhouse’s busiest week.

Ottawa’s Christine Dobson was among the dozens out perusing their selection Sunday, shopping for planters and perennials after recently redesigning her family’s yard.

“We wanted to find a balance between the look that we were aiming for … but also being true to the climate that we live in,” Dobson said.

While updated hardiness zones create opportunities for gardeners to experiment, Pedlar said it also reflects broader climate change.

For now, the changes to the map remain minimal.

“It doesn’t mean Ontario is suddenly going to start growing bananas.”