Understanding Hardiness Zones

We’re living in times of changing climates and rising food insecurity.  There are a number of factors that go into both, which we will not go into here, but both issues are causing a return to home food gardening.

At the Brar house, in Toronto, we raise a lot of our own food.  From herbs like cilantro, basil, rosemary, dill, amaranth, chives and oregano to vegetables like tomatoes, cucumber, pumpkin, zucchini, peppers and chilies that are a staple of our diet to the most delicious apples from our Macintosh apple tree and pears and even figs!  We love us some figs.  We do all of this on a ravine lot in a northern Toronto neighbourhood – in the yards and on our small, second story deck.

I’m a rather “let’s see how it goes” type so my first year of growing my own garden was a bit of an experiment.  I did not read seed packets and plant tags as well as I should have.  It was essentially – sun?  Okay, you go here.  Shade?  Already then, over here with you.  Water a lot or a little, and plant so many cm apart.  I completely ignored the information each package or plant gave me.  I mean, why would they sell me the plant or seed in the local hardware store parking lot if it won’t do well?  Huh?  WHY?


What is a Hardiness Zone?

Hardiness zones are very important to the health of your plant and Canada has a massive range of zones.  A hardiness zone tells you what regions in Canada a certain plant is best suited to thrive in.  In Canada, we have regions from zone 0a (much of the Arctic) to 9a (a very tiny area on the Southern tip of Vancouver Island).  The Brar house is located in zone 7b (and drifting into warmer zones with every season).  Which meant absolutely nothing to me until I learned to be more efficient with growing my own food.  You can locate your own zone within Canada here.

Hardiness zones apply to both perennials (plants that return year after year if they can survive the winter) and annuals (because the length of the growing season is also important to these plants).  The zone map applies only to outdoor planting however, and not indoor or greenhouse planting where lighting and climate conditions are more controlled.


What the Heck Grows in Zone 0A?

Only the very hardiest plants that have adapted to the special conditions of the high Arctic will survive a winter outside in Zone 0a.  Subalpine fir, longbeaked sedge, lichens, a variety of spruce species… and you thought it was all empty.  The high Arctic that composes most of zone 0a and 0b is a fragile but incredibly diverse set of ecosystems.  The fact that climate change is damaging the Arctic should be of concern to all of us and is dear to me as a former resident of this amazing land.


Selecting Plants Based on Hardiness Zones

Most plants will survive in the hardiness zone listed on its seed pack or plant tag, given all other conditions are optimized (light, watering, soil type, etc).  They will thrive a little better in one zone warmer.  Going any warmer than that, you may risk introducing an invasive species (one that does so well it chokes out plants that are native to the region) or it may fail altogether because it has the wrong soil and light conditions.  Going in the other direction, a plant that is perennial in one zone will become an annual in colder zones.  It may grow outside for the summer season but it will not survive the winter outdoors.

You can solve this problem by bringing plants indoors during the colder conditions or into a greenhouse.  We’ll cover how to harden and soften plants in a later post.

A hardiness zone indicator is no guarantee that your plant will thrive.  Hardiness zones change with climate change so something that has done well for decades may begin to fail if its zone changes.  For example, Toronto’s hardiness zone has warmed two full zones in 20 years.  Plants also require the right amount of sunlight and water, and proper soil and spacing conditions.  To complicate matters further a tar topped, over the garage deck will have its very own zone because it is so much warmer for longer than the ground.  A built-out deck will have another zone because it’s cooler.  For example, I grow chili peppers on the upper, tar-topped deck from as early as the beginning of April until as late as Remembrance Day.  It’s that hot up there.  Some species of chili (scorpion, Thai and Scotch bonnets) do well on the ground in a semi-shaded area, while I have only been able to grow Kashmiri chilies on the shaded side of the deck.

All this to say, pay attention to the hardiness zone information that is printed on your seed packs or plant tags.  If in doubt, ask your gardening centre, or look here for a great list of plants that will grow well in many zones.


Toronto Hardiness Zones

In the northern edge of Toronto, a small list of some of the food crops that will do well include:

Blackberries                                       Chestnut                                             Hazelnut

Persimmon                                         Plum                                                    Walnut

Garlic                                                     Dandelion                                         Cranberry (bush)

Maple                                                   Cherry                                                 Strawberries

Peas                                                      Black currant                                     Red currant

Prickly pear                                         Brown mustard                                Flax

Mulberry                                             Sunflower                                           Mint

Grapes                                                 Gooseberries                                      Raspberries

Asparagus                                           Parsnip                                                Carrot

Potato                                                  Onion                                                   Rose

Blueberry                                            Oats                                                     Corn

Rye                                                        Apple                                                  Sweet Peppers

Ultimately, if you want your food crops to survive well, beyond paying attention to soil quality, water and sunlight, you do have to pay attention to heartiness zones.  In future posts, we’ll deal with how to turn annuals into perennials, seed saving and when to plant but for now, we hope we’ve given you some new information to make the most of your home garden!

Peace and love all,



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