If you’re planning an outdoor cannabis grow in Markham this spring, there’s one thing every successful grower knows:
Timing, genetics, and climate awareness matter more than a green thumb.
Why? Because Markham — like much of Southern Ontario — doesn’t give you a long outdoor season. Gardeners see the last average frost around May 10–15, and the first significant fall frost often hits as early as mid-October. That gives you roughly 160–170 frost-free days to work with — and that’s assuming ideal weather.
The window between spring’s promise and fall’s claws is narrow, which is why more Markham growers are choosing cannabis clones instead of seeds — especially when the goal is a strong, stress-free harvest.
This guide breaks down:
But before moving ahead, check out our Outdoor Spring Bundle Pack 1 and Outdoor Spring Bundle Pack 2 or the best yield!
Let’s start with a reality that too few beginners factor in:
Seeds are unpredictable.
On average, germination takes 7–10 days, then another 10–14 days before seedlings are vigorous enough to transplant. That can easily total 3 weeks or more lost before a plant even gets a real start.
In Markham — where you effectively have 5 months of reliably warm weather — losing three weeks means losing about 20% of your entire outdoor growing season.
Cannabis clones solve this by arriving:
When fall temperatures can dip below 5°C in late September, that early advantage becomes critical.
This is where many growers make their first big mistake.
You don’t want to wait too long — but you also don’t want to plant too early.
Here’s a reliable timing pattern Markham growers follow:
👉 Late March through early April
This is your sweet spot:
Read more here!
👉 Mid-May to early June
Even if daytime temperatures feel warm earlier, Markham nights can stay below 10°C well into May — and cold nights can stall clone growth, sometimes for up to two weeks.
Experienced growers keep their clones in a protected area for a few weeks, gradually exposing them outdoors only when nighttime lows stay consistently above ~10°C.
Thanks to Markham’s proximity to major Ontario shipping hubs and the GTA, delivery from Canadian clone suppliers is typically fast — 1 to 2 business days.
That short overnight transit window significantly reduces stress on the plants compared to long-distance shipping.
When your clones arrive, check for:
Once they arrive:
That recovery period is crucial for reducing shock and encouraging strong early growth.
Not every strain will thrive outdoors in Southern Ontario — and that’s okay because there are genetics that do well.
Markham growers who consistently get good results choose strains that:
✅ Finish flowering in 7–9 weeks
✅ Show resistance to mold and mildew
✅ Handle variable spring and fall conditions
✅ Grow to a manageable height
Read more about trending spring clones here!
A mistake many beginners make is choosing slower-finishing strains that take 10–11 weeks to flower — in Markham that often means ripening too late, risking lower potency and weather damage.
If you’re looking for curated options with balanced performance and outdoor readiness, grow packs like the Outdoor Spring Bundle Pack 1 and Outdoor Spring Bundle Pack 2 take much of the guesswork out of strain selection.
Here are the practical, boots-on-the-ground tips experienced Markham growers use every spring:
For the first 7–10 days after delivery:
Cold nights and strong sun during the day can stress young clones — gradual transition prevents shock.
Markham nights under 10°C are still too cold for young clones. Even if daytime highs hit 18–20°C, cool nights can slow growth dramatically.
Experienced growers wait until nights stay consistently above 10°C before full outdoor planting.
It’s tempting to “get outside early,” but cold snaps are common through April in Southern Ontario.
Planting too early can delay growth, costing you weeks of valuable season time.
Young clones do best with:
Lake Ontario winds can be stronger than expected, especially in early spring.
Most years, no. April nights are too cold, and even cool daytime weather can stall growth.
Yes — especially when the goal is finishing before fall, and every day matters.
Most adults plant up to four per household, so plan your space and genetics accordingly.
Your outdoor cannabis grow in Markham doesn’t begin in July — it begins the moment you decide how you’re going to manage timing, genetics, and local weather.
Clones won’t solve every problem, but they take at least three weeks of uncertainty off the table, giving you more time to grow strong, healthy plants.
If you’re planning your best season yet, now is the time to secure your clones and plan for a smooth, frost-free run.
Explore spring-ready cannabis clones and outdoor-optimized bundles shipped directly to Markham and the GTA — and give your grow the best possible start.
After 30 years of mastering the craft of producing the best cannabis clones in Canada, we launched Mr. Clones to give home growers and professional cultivators convenient access to premier strain-verified cannabis clones. All information on this website is for general informational purposes only and is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment.
