Seed Starting By Grow Zones In Canada

Ashley

Do Growing Zone Matter For Seed Starting In Canada

Gardeners are obsessed with their growing zones. In Canada, we have endless influencers popping up with tips and tricks specific to their growing zone. But is this necessary? Is gardening in Canada truth this narrow and specific? Let’s take some science and look at exactly what it means to use growing zones for seed starting. And whether or not growing zones matter for seed starting in Canada. Let’s look at Seed Starting By Grow Zones In Canada.

If you are new to this blog my name is Ashley and I am a soil scientist. I am located in a Canadian Zone 3 and a USDA Zone 4. I write articles, make YouTube videos, Instagram & Facebook posts all designed for Canadians and Cold Climate gardeners using science-based methods. If you are looking for anything specific be sure to let me know in the comments down below.

Growing Zones & Seed Starting With Growing Degree Days

What Does Days To Harvest On Seed Packets Mean? Why Do The Days To Harvest Never Line Up!?

Growing zones are made by agriculture and agri-foods Canada but are reviewed regularly. So if you thought your growing zone was zone 4 and not is suddenly zone 5 this is entirely possible. They are determined by temperatures, elevations, moisture and a number of other factors. But when it comes to looking at whether or not growing zones matter for seed starting the key is the number of growing days.

This comes down to Growing Degree Days (GDD) a concept that is very well understood. Ultimately the number of growing days you have directly affects the GDD’s that can be achieved in your zone. The exception to this entire rule is the use of outdoor season extenders such as tunnels and cold frames. For more on this concept check out the video series of Growing Degree Days for gardeners. 

So if we consider GDD and the total number of growing days for our zone we immediately realize that indoor starting doesn’t matter. The earlier starts to seeds will not equal a faster yield, nor do they mean a potential yield for longer growing season plants. Let’s look at two different situations that most gardeners encounter at some point in time.

How To Calculate Growing Degree Day...
How To Calculate Growing Degree Days For Your Garden. Using GDD To Plan Your Seed Starting Times

Wave Planting And Faster Yields

As beginner gardeners, we often encounter this issue despite our best math skills being used. We sow tomato seeds indoors a month apart with the intent of having fruits appear a month apart. We calculate that 90 days from mid-March means our first tomatoes will be ready for mid-June. But when mid-June rolls around we quickly realize that there aren’t even flowers appearing yet let alone fruit. 

This is due to the GDDs and the reality that earlier does not mean faster harvest. Save yourself the stress of handing giant plants and potential transplant shock. When the seeds say start your seeds 8-9 weeks before the last frost, start the seeds 8-9 weeks before your last frost. 

Planting Plants In Canada With 120+ Days To Harvest

As a gardener in a Canadian growing zone 3, zone 4 or even zone 5 you may have bought seeds with 120+ days to harvest. The hope is if you start them early and baby them you will get fruit. But in reality, this never ends up happening and instead, you end up with a plant that’s very large and mostly green.

This is due to the total number of days in your zone combined with the growing degree day units you can acquire. The key is to look at the total number of days you have and determine if the days to harvest fall into that realm. If you are short by more then 10 days it is unlikely you will get any results without some form of season extender. If you are short by more than 5 days and don’t intend to insulate against nights getting below 10 degrees celsius then again it is unlikely you will see any great results. 

When To Start Seeds By City In Canada
When To Start Seeds By City In Canada

8 thoughts on “Seed Starting By Grow Zones In Canada”

  1. I think you have a typo in the last frost date for Thunder Bay? I live in Thunder Bay, and the local plant people always say last frost date is June 6, and I’ve looked on 6 different websites including Environment Canada, and they all say the first week of June. There is no way that Thunder Bay has a shorter growing season that Yellowknife.

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