GARDENING ZONES BY THE NUMBERS
I don’t want to alarm you, but it gets cold in Alberta. And not just chilly, but it-hurts-when-I-breathe cold. On the plus side, we don’t have to worry about the Zika or Ebola viruses, or flesheating ants. On the downside, we can’t grow any of the plants you saw on your last tropical holiday.
When it comes to plant options, we still have thousands of varieties to choose from, and I would argue that we have hardy plants as gorgeous as any hibiscus or bird of paradise. When you go to the garden centre, however, how do you know which plants are reliably hardy and which need extra care?
1 Check the tag of any tree, shrub, or perennial and you’ll find a zone number. That is your guideline for how tough the plant will be. In other words, will you need to trim and mulch and fret over it, or can you just plant it and enjoy?
2 Hardiness zone map Natural Resources Canada has created the Canadian zone map. I use this map as reference, but keep in mind that the latest version was published in 2000 and used data gathered no later than 1990. It goes without saying that our climate is significantly different now than it was 26 years ago.
Canada has eight climactic zones, ranging from 0 (Nunavut) to 8 (Victoria). Each of these zones is divided into an ‘a’ and a ‘b’ (with ‘a’ being colder and ‘b’ being warmer) but you don’t need to worry about the letters. While the map marks Edmonton and the surrounding area as ‘3a’ (a ‘warm’ zone 3) we can grow many Zone-4 plants very well and, depending on where you live, even zone 5 plants.
3 Deciphering the numbers Here’s what you need to know about the numbers that affect us:
Zone 2 plants (minimum temperature -45 C): These plants grow with practically no care. You would be surprised at how many varieties, and how much colour, can grow in this zone.
Zone 3 plants (minimum -40 C): This is our standard zone for a reliably hardy plant. You can water in the fall and winterkill will rarely be an issue.
Zone 4 plants (minimum -34 C): If you want to grow a slightly more exotic plant it’s possible, but you’ll have to work for it. Expect to mulch in the fall.
Zone 5 plants (minimum-28 C): These plants are for experienced gardeners and gamblers only, as they need shelter and extensive fall care. You’ll have a slightly easier time if you live in an urban area.
Zone 6 plants (minimum-23 C): Forget these ones. I’m including them because, just to make things more confusing, some Zone 6 plants like “purple fountain grass” will say perennial on the tag. It’s a question of where the tags are printed. If you’re unsure if something is hardy, even if it says perennial, always be sure to ask.
4 Pushing the zone Part of the human condition involves never being satisfied, so for those of you who don’t shy away from starting plants geared toward zones 4 and 5, here are some tips:
In the fall, remove any dead or diseased foliage/branches. Water very well — until the roots are like a stick in a frozen Popsicle — and mulch with disease-free material. Shovel snow on them throughout the winter (especially if there’s not much snowfall) for insulation. Don’t even try Zone 5 plants unless you have a very sheltered area. If you live in a built-up area you gain a few degrees, and even better if you have a spot with wind breaks around it (but one that still gets enough sun).
5 Low-maintenance plants My yard is full of Zone 2 and 3 plants. I know that I can plant them and that they will survive, thrive, and be beautiful. After the first year, I don’t water at all unless it’s a dry month. Zone 2 and 3 plants grow quickly, bloom freely, and attract scores of pollinators and other beneficial insects. While they are not the most exotic plants, there are thousands of them available, with a look for every taste and personality.