I am trying to comprehend Canadian hardiness zone information provided on the government’s website. It is not easily converted to the American system, so knowing which system is in use when making a purchase is important to me.
I am wondering if TMGs can say with certainty that all garden plants sold in our region are labelled with the corresponding Canadian hardiness zones? Or are some labelled with the American system? How can one tell the difference on a commercial label?
Thank you for contacting Toronto Master Gardeners. This is a great question as not all labels provide the growers location or country of origin.
Plant Hardiness Zones information that will assist you in comparing Canadian zones with USA zones can be found on our website: http://Plant Hardiness Zones .
By municipality: Zones by Municipality
This website if you scroll down will have the US Hardiness Zone and which part of Canada to apply the US listed zone: US Hardiness Zone Applied to Canada Zones
There are many different suppliers, each with their own labelling, due to the products they specialize in. For example, some suppliers specialize in just trees, or fruit trees, roses, shrubs, native plants etc. As you do not mention the type of plants you are particularly interested in as having Canadian/American Zone labels, I am going to assume you are asking about trees, shrubs, and perennials, also including hardy or non hardy bulbs. I am also assuming you are not referring to annuals grown in our zone as they do not overwinter.
The name of the grower and their geographical location will be a good indicator of Canadian Hardiness Zones. Are plants grown in Canada – Ontario, Quebec, British Columbia or the United States? Buying locally grown plants will guarantee a Canadian Hardiness Zone. There are many growers in Ontario such as Grow Wild Native Plant Nursery located in Omemee that supply many retailers with native grown perennials. Their labels list Canadian hardiness zones.
Nurseries and garden centres can also provide the plant suppliers’ information and location with a website if available. Having worked at a Loblaw garden centre, I know that information was readily available when requested. Even if they do not have a specific growers name they can confirm where they were shipped from. Even if grown by a non-owned Canadian company, some growers such as Proven Winners have propagators in Canada that supply retailers: Proven Winners Propagators. The Canadian propagated plants are grown in Ontario and therefore will have Canadian Hardiness Zones.
Tulip bulbs, daffodils, many other non native bulbs will come mostly from Holland and are packaged by individual retailer, e.g. Brecks who reflect Canadian Hardiness Zones. Look at the packages for planting instructions. Brecks Tulip – Reflect CAN Zones
The most recent labels found in garden centres or retail stores, e.g. Canadian Tire or Home Depot, have descriptive perennial labels. Canadian Tire labels will have the growers name, list that the plant is grown in Canada, along with the plant Hardiness Zone 5 (-28C/-20F).
Not all labels have the growers name or website which you can research to confirm where the plants are shipped from and which Plant Hardiness Zone they are using. Not having that information, I would suggest you look up the plant by botanical name on a Canadian website, research its growing conditions and Canadian Plant Hardiness Zone. For example, researching native plum (Prunus americana), Native Plum Hardiness Zone