Zone 5?

Hello Friends,

Have you noticed the plant tags on our trees say Zone 5? Please read on.

For many retail nurseries/garden centres it's not uncommon to buy from US suppliers. Our main supplier of trees is located in BC, Canada. I mention this because I've noticed that the plant tags on the plants from our supplier appear to be listing the US hardiness zones as opposed to the Canadian ones. This is actually a big deal because the two scales are different. The US scale is based solely on extreme low temperatures while the Canadian scale is based upon seven different variables. Yup, seven! So, the US and the Canadian scales do not match up number for number.

Look, our main supplier does excellent work with their grafting, the quality of trees they provide as well as, an incredible selection for retailers like us to choose from. I also know however, that there are a few mistakes made with spelling of tree names or other minor tree details. It happens. And I think the hardiness zone of 5 listed on their plant tag is probably not most representative for Japanese maples in Canada.

Fortunately, I know that most if not all of our customers are well aware of whether or not Japanese maples can be grown in their area or whether they need to go into the garage in the winter. And we've done our best to help provide information on this topic. However, coming back to the zone system, a US zone 5 and a Canadian zone 5 are not the same. In fact, you can roughly bump up the number by 1 for Canada. So, a US zone 5 is approximately a Canadian zone 6 (It might be 5b or 6a). If you're in a cold area this could be critical. Again, the two scales cannot be accurately compared, this is an approximation. 

Now many, but not all, Japanese maples planted in the landscape can survive down to close to -30C temperatures. Container plants should not be expected to be so lucky. In our area, we are about a 6b, so temperatures typically have a lowest low of -23C. In our nursery, we have many trees that have survived in containers, buried under the snow, in frigid temperatures during our first winter here. The snow provided insulation, yes, and we did lose some trees. But most survived. And I'm almost certain there was one night this past winter where we did't have heat in our greenhouse and the temperatures got to -20C without any noticeable tree losses as a result. But a week of -20C with no heat on these containerized trees may have told a different story.

Bottom line is, the plant tags are not specific to each variety of Japanese maple, but rather generalizing for all. Ideally, our supplier plant tags would say zone 6 but they don't. And even this would be a single number for a broad swath of plants that have varying winter hardiness, some below zone 6 and some above. 

If you're not sure about your growing zone you can find links on the Growing info page under The Basics on our website homepage. Here's the page

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