Français The best time to plant cannabis outdoors in Canada is after the last spring frost, once nights stay above about 10 °C. In much of the country that means mid-May to early June, with earlier dates on the West Coast and later ones in the mountains and the north. Start seeds indoors a few weeks earlier, harden the seedlings off, and plant out when the forecast is stable.
Calendar
Your outdoor season at a glance
Start indoors in spring, plant out after the last frost, and harvest before the cold of autumn.
Fast version seeds
Wait for the last frost
Frost kills cannabis seedlings, and cold nights slow older plants. Frost dates vary a lot across Canada, from April on the southwest coast to early June in parts of the Prairies and the mountains. Look up the average last-frost date for your town with Environment and Climate Change Canada or a local gardening almanac, then add a safety margin of a week or two, because late cold snaps are common.
| Region | Typical time to plant out |
|---|---|
| British Columbia coast | Late April to mid-May |
| Southern Ontario | Mid-May |
| Quebec and the Ottawa Valley | Mid-May to late May |
| Atlantic provinces | Late May to early June |
| Prairies and interior British Columbia | Late May to early June |
These are typical ranges, not guarantees. Always confirm them against the last-frost date for your own area.
Timing for autoflower and photoperiod plants
By seed type
Two different calendars
Autoflower
Plant out from late May to early July
Autoflowers flower on their own and usually finish in about 10 to 14 weeks. You can plant them after the last frost, or even in early summer, and still harvest before autumn.
Photoperiod
Plant out by early June
Photoperiod plants need time to grow before the nights lengthen after the summer solstice. Planting out in late May or early June gives them a full season of growth before they flower in late summer.
For a closer comparison, read our guide to autoflower vs photoperiod seeds.
Start indoors, then harden off
In a short northern season, a head start matters. Germinate seeds indoors three to four weeks before you plan to plant out (our guide explains how to germinate cannabis seeds), and keep the seedlings under strong light so they stay compact.
Before planting out, harden the seedlings off. Over seven to ten days, put them outside for a few hours in a sheltered, shady spot, then lengthen the time and add direct sun. Bring them back inside on cold nights. This avoids shock from wind, sun and temperature swings. Our seedling tips cover the first weeks in more detail.
Choose the site and the variety
Pick a spot with at least six hours of direct sun a day, shelter from strong wind, and soil or containers that drain well. Containers let you move plants if a cold snap or storm is on the way. Choose varieties that finish before autumn: early, fast version and autoflower varieties are the usual picks for the Canadian climate. See our list of the best outdoor strains for Quebec and our advice on getting big yields outdoors.
Checklist
Before you plant out
Check each item first.
Protect plants when the weather turns
Keep covers or frost cloth handy in spring and autumn, and move containers indoors when frost is forecast. In autumn, harvest before the first hard frost, or cover plants on cold nights to gain a few extra days. Cool, damp autumn weather also raises the risk of mold in dense flowers, so read our notes on temperature and humidity.
Cannabis laws vary by jurisdiction, including how many plants a household may grow, so check the rules where you live before you plant.
Common questions
When is it too late to plant cannabis outdoors in Canada? For photoperiod plants, planting after the end of June leaves little time to grow before flowering and the cold of autumn. Autoflowers can go out until early July in many areas, as long as they can finish before the first frost.
Can cannabis survive a light frost? A hard frost kills cannabis, and even a light frost can damage leaves and slow growth. Cover plants or move pots inside when frost is forecast.
What night temperature is safe for cannabis outdoors? Growth slows below about 10 °C, and frost kills plants. Wait until nights stay above about 10 °C before planting out.
Can I sow seeds directly outdoors? Yes, once the soil has warmed and the frost has passed. Starting indoors gives a head start and protects young seedlings from cold, wind and slugs, which often matters in a short season.
How long does outdoor cannabis take to grow? Autoflowers usually take about 10 to 14 weeks from seed. Photoperiod plants grow all summer and are usually harvested from late September to October, depending on the variety and your region.
The northern season, month by month
| When | What you are doing | What decides success |
| Mid-April to early May | Germinate indoors under light | Starting now is what buys you the extra three or four weeks the season does not give you |
| Mid to late May | Harden off over 7 to 10 days | Going straight from a tent to full sun and wind stalls plants for a fortnight |
| Late May to early June | Transplant outdoors after the last frost | Soil temperature above 12 °C. Cold roots do not grow |
| June | Vegetative growth, training | Topping or LST now; the plant has the time to recover |
| Early July | Flowering begins as days shorten | Stop training. Switch feeding toward bloom |
| Late July to August | Peak flowering and bulking | Heat and humidity management; this is when mould risk starts |
| September | Ripening, early strains finish | Cold nights and rain. The month that decides your crop |
| Early October | Late strains finish; first hard frost | Harvest before a hard frost, not after |
Choose the strain by harvest month, not by flowering time
Indoor flowering time is the number most seed listings lead with, and outdoors it is the wrong number. What matters is the date the plant is actually ready in the ground. We group our outdoor seeds by harvest month for exactly this reason, so you can filter to what finishes in time instead of converting weeks of flowering into a calendar date and hoping.
- September finishers are the safe choice anywhere in the region, and the only sensible choice in zone 4. They come down before the weather turns.
- Early October finishers work in the warmer pockets — the Montréal area, southern Ontario, the Fraser Valley — if you have a sheltered spot and are willing to watch the forecast.
- Mid to late October finishers are an indoor strain here, whatever the listing says.
- Autoflowers sidestep the calendar entirely. They flower on age rather than daylight, so you can plant in June and harvest in August, or run two cycles in one summer.
What actually goes wrong in a short season
Cold September nights
This is the single most common cause of a disappointing northern harvest, and it is not the frost that does it. Nights below about 15 °C slow nutrient uptake and cause premature yellowing, and sustained cold can stress a plant into producing pollen sacs. If your nights are dropping and the plant has two weeks to go, covering it overnight is worth the effort.
Autumn rain and bud rot
Dense flowers plus a wet week equals botrytis, and it moves fast enough to take a bud in two days. Airflow is the defence: space plants, strip the lower growth, and shake water off after heavy rain. If rot appears, cut well past the affected area immediately rather than hoping.
Starting too late
A seed germinated outdoors in June will not have the vegetative time to produce much before daylight shortens and flowering starts. Indoors in April, outdoors in late May, is the schedule that works.
Planting out too early
The opposite mistake. A late-May frost kills seedlings outright, and cold soil stunts the ones that survive. Watch the soil temperature rather than the calendar.
What gives you the most extra season for the least effort
- Start indoors in April. Worth three to four weeks of growth, which is the difference between a small plant and a real one.
- Use fabric pots you can move. Being able to pull plants under cover for one cold night or one wet weekend saves more crops than any other single measure.
- Plant against a south-facing wall. The stored heat raises the local night temperature by several degrees.
- Pick a September strain. The cheapest insurance available, and it costs nothing.
- Have a cover ready before you need it. A frost cloth bought in August is useless if it is still in the shop in September.
Frequently asked questions
When should I plant cannabis outdoors in Quebec?
Transplant outdoors after the last frost, usually late May to early June, once soil temperature is above 12 °C. Start the seeds indoors in April so the plants are already established. Note that home cultivation is prohibited in Quebec itself; the timing applies to any comparable northern climate where growing is legal.
When is the last frost in Quebec?
Typically mid to late May in the Montréal area and zone 5, and into early June further north in zone 4. Local conditions vary, so use your own area's frost dates rather than a provincial average.
When do you harvest cannabis in a northern climate?
September for early strains and early October for later ones. The first hard frost usually arrives in early to mid-October, and you want to be finished before it, not racing it.
How long is the outdoor growing season in Quebec?
Roughly 130 frost-free days in zone 5 and about 110 in zone 4. That is short enough that strain choice matters more here than almost anywhere else.
Can cannabis be grown outdoors this far north at all?
Yes, and well. The summer is warm and the daylight is long. The constraint is the two ends of the season, not the middle, which is why starting indoors and choosing an early finisher matter so much.
Are autoflowers better for a short season?
For a short season or an uncertain spot, often yes. They flower on age rather than daylight, finish in roughly ten to twelve weeks from seed, and let you harvest in August before the weather turns. You can also run two cycles in one summer.
What strains finish earliest outdoors?
Look for September harvest dates. Our outdoor seeds are grouped by harvest month so you can filter to the September finishers directly rather than reading flowering times and guessing.
Is it legal to grow cannabis at home in Quebec?
No. Federal law permits four plants per household, but provinces may restrict further, and Quebec prohibits home cultivation entirely. The Supreme Court of Canada upheld that ban on 14 April 2023 in Murray-Hall v. Quebec. Growing at home is legal in most other provinces, subject to their own rules, so check your own province before you plant.
Who is this guide for, then?
Anyone growing in a short northern season where it is legal to do so. Ontario, the Maritimes, the Prairies, the BC interior and the northern United States all face the same calendar Quebec does. The genetics are bred here; the growing advice applies wherever the summer is short and the autumn arrives early.
