Do you know what growing zone you’re in?

With gardening season upon us, you may be scouring the Internet for tips and tricks on how to plant and manage your yard. In many articles, you've probably come across the terms “hardiness zones” or “growing zones”, or seen references to Zone 7A or hardy to Zone 5 in gardeners’ social media posts and wondered what on earth they were talking about.

Knowing your zone is important in order to select the plants that will grow best in your area and environment. It’s less overwhelming than it seems, so let’s break down “planting” or “hardiness” zones and figure out where your garden lands.

What are hardiness zones?

Zones are regions with similar temperatures and specifically similar temperatures for the coldest days of the year. These are known as “average extreme minimum temperatures” which are placed into categories 1 to13 (coldest to warmest regions) and then each number is further broken into two subcategories “a” and “b”.

Canada’s hardiness index is modelled as a function of seven different variables that influence plant survival and growth: mean minimum temperature of the coldest month, frost-free period in days, rainfall June through November, mean maximum temperature of the warmest month, rainfall in January, mean maximum snow depth, and maximum wind gust in 30 years.

Phew, that’s a lot of things to consider! And since having the index handy, gardeners and farmers have been able to rely on this research to know which plant varieties will hold up in their growing zones and survive the coldest of days to the warmest peaks.

You can find your growing zone in Canada here (which is different from your average frost dates and different from the USDA Growing zones).

Why do plant hardiness zones matter?

Knowing your region’s hardiness zone will help you to understand what types of vegetables, fruits, flowers and trees to grow in your area. If you know that you have a longer warm period, you’ll be able to grow seeds that are 100 days+ to maturity, but if you live in a colder zone, you may want to stick to peppers that are 60 days to maturity.

It’s important to keep in mind that some seed packets list the days to maturity from when you transplant your seedling (not from when you’re starting your seeds). For seeds that take extra time like celery, squash, eggplants, peppers and tomatoes, you may want to start them indoors under a grow light so you have enough growing time outside once the danger of frost has passed.

Understanding your plant hardiness zone will allow you to look at seed packets and know whether or not that seed is adapted to your region, or whether you would need to grow it in a greenhouse or under row cover. It will save you time and money to grow the right plants for your area.Eggplant gardeningPexels/Zen Chung

Know your zone, but still take notes

Although these maps are useful, they have a few limitations. Since they apply a single formula for the entire country, there may be some climatic variables that aren’t taken into consideration, especially as the climate evolves and warmer temperatures and unpredictable weather patterns are on the horizon.

As wonderful as it is to know our growing zones for the initial days of planting and preparing for our gardens, it’s more reliable to create a gardening journal where you can document the weather on given days and months, then go back and compare throughout the years. It’s also handy to grow seeds that are adapted to your region by saving your own successful seeds from past years or trading them with your local community.

The perk of knowing your hardiness zone is you’ll know when the ideal time is to plant cool-season crops like cabbage, greens, roots, potatoes and onions, or when to give a little extra time to your warm-season lovers like tomatoes, peppers, cucumbers, squash, beans and corn. Hardiness zones grant us the gift of planning, which is the key to a successful garden with a plentiful yield.