Canada’s plant hardiness zones map ready to bloom for 1st time in 10 years

Natural Resources Canada is working on the first update to its plant hardiness zones map since 2014, hoping to have the map – which gardeners rely on when determining what plants will thrive in their region – available sometime in 2024.

The update comes on the heels of the United States Department of Agriculture’s latest plant hardiness map, updated last month for the first time since 2012, which NPR reported saw roughly half the country shift into a new half zone as temperatures warm.

However, the USDA’s map relies solely on extreme temperatures, while Canada’s map takes into account seven factors, making predicting potential zone changes a little more complicated.

Still, early observations suggest change is coming more rapidly in Canada’s North and West compared with the East, where in some rare cases, researchers say there’s been a decrease in extreme minimum temperatures.

What is a plant hardiness zone?

In the simplest terms, the plant hardiness zone map shows what can grow where. The zones go from 0 to 9, and each zone is divided into two: a and b.

“When you’re at the greenhouse and you’re purchasing plants, you’re always reading the tags to see what zone it belongs in,” says Sandra Mazur, second vice-president of the Ontario Horticultural Association and member of the Dryden Horticultural Society and the Thunder Bay Horticultural Society.

“That’s one of the questions that we get on all of our websites all the time from new gardeners, they’re always looking to see what zone they’re in.”

Much of the three territories falls under the 0 and 1 zones, while the northern middle of the provinces hovers around zones 2 and 3. Areas where much of Canada’s population is concentrated, farther south, tend to be in the 4, 5 and 6 zones. Victoria is the sole location to be listed as 9a in the 2014 map – a zone that didn’t exist in previous versions of the map.