Cannabis Seeds in London, Ontario
If you are growing cannabis in London, the first thing you need to understand is that conditions here are specific. London sits in southwestern Ontario's agricultural belt, between two Great Lakes. The rich farmland soil is naturally fertile for cannabis, but the lake-effect weather patterns bring more cloud cover and precipitation than areas further from the lakes.
London sits in southwestern Ontario's fertile agricultural belt. The region's rich soil and moderate climate (moderated by Lake Huron and Lake Erie) make it one of Ontario's better outdoor growing locations. London's university community has also contributed to a knowledgeable and experimental growing culture.
London's elevation is modest but the surrounding flat agricultural land means wind exposure is higher than in sheltered urban gardens. South-end neighborhoods closer to the 401 corridor tend to be slightly warmer.
What Makes Growing in London Different
Climate Reality
- •Frost-free period: 150-165 days (mid-May to mid-October)
- •Average summer high: 27°C
- •Summer humidity: moderate to high (65-80%)
- •Primary growing challenge: lake-effect moisture from both Lake Huron and Lake Erie
London sits in southwestern Ontario's agricultural belt, between two Great Lakes. The rich farmland soil is naturally fertile for cannabis, but the lake-effect weather patterns bring more cloud cover and precipitation than areas further from the lakes.
London's elevation is modest but the surrounding flat agricultural land means wind exposure is higher than in sheltered urban gardens. South-end neighborhoods closer to the 401 corridor tend to be slightly warmer.
Best Strategy for Growing in London
Recommended approach: outdoor growing with humidity-aware strain selection, indoor through winter
A common approach in London is indoor growing as their primary method, using autoflowering seeds that finish in 8-10 weeks per cycle.
For outdoor grows in London, start seeds indoors by early April and transplant outdoors around late May. Target your harvest for late September to early October. Watch for September moisture — London gets more precipitation than Toronto in early fall — this is when most London outdoor crops face their biggest threat.
University-city mix of older homes near Western University and newer suburbs. Many properties have adequate yard space for outdoor growing.
Common Mistakes in London
1. Not matching strains to London's specific conditions. lake-effect moisture from both Lake Huron and Lake Erie is the defining challenge here. Generic strain choices that ignore this fail.
2. Skipping daily bud inspections in late summer. In London's humidity, mold can appear overnight. Catching it early saves the rest of the harvest.
3. Germinating seeds in a cold room. Cannabis seeds need 22-26°C to crack. London basements in early spring can sit at 15°C without you realizing it. A simple heat mat solves this — see our germination guide for the full technique.
When to Start and When to Harvest in London
| Stage | Timing for London |
|---|---|
| Start seeds indoors | early April |
| Transplant outdoors | late May |
| Harvest window | late September to early October |
| Risk period | September moisture — London gets more precipitation than Toronto in early fall |
| Frost-free days | 150-165 |
Watch for: September moisture — London gets more precipitation than Toronto in early fall. This is when most London outdoor growers face their biggest decision: harvest now or risk one more week. In our experience, harvesting slightly early beats losing the crop to weather.
Strains for London Growers
Based on London's specific conditions — 150-165 frost-free days, moderate to high (65-80%) humidity, and lake-effect moisture from both Lake Huron and Lake Erie as the main challenge:
- •Northern Lights Auto — finishes in 8-9 weeks from seed. In London, this timing means harvesting by late September, well ahead of September risks. autoflowering seeds like this one are the safest outdoor choice given London's frost calendar.
- •White Widow — handles London's moderate to high (65-80%) humidity better than dense-budded alternatives. Mold resistance is the priority in these conditions.
- •Blueberry Auto — a fast backup option. We have seen London growers succeed by running this alongside their primary strain for variety without sacrificing speed.
- •Critical Mass — strong indoor performer for London's winter growing season. Works well in the environmental conditions typical of London homes.
Browse autoflowering seeds for more fast-finishing options or feminized seeds for larger yields. Not sure which type? Our cannabis seed types explained explains the trade-offs.
Buying Seeds in London
How London growers typically source their seeds — and why most end up ordering online:
Local retail in London carries a limited selection from a small number of licensed producers. Government retail stores in Ontario may have 10-15 seed varieties at most. The staff may not have growing experience specific to London's conditions.
Online seed banks give you access to over 1,000 strains from dozens of breeders. More importantly, you can choose strains specifically suited to London's 150-165 frost-free days and moderate to high (65-80%) humidity — that level of precision does not exist on retail shelves. Seeds start at $9.99 CAD, free shipping over $99, and everything arrives in plain packaging within 2-4 business days.
The practical difference: a local shop might have one autoflowering seeds option. We carry dozens, including strains specifically bred for the mold-resistant strains traits that matter for growing in Ontario.
Delivery to London
Seeds ship to London from within Canada via Canada Post. No customs, no border issues.
- •Delivery time: 2-4 business days to London
- •Free shipping on orders over $99 CAD
- •Plain, unmarked packaging — no logos, no cannabis imagery
- •Tracking number emailed after shipping
- •Germination guarantee — follow our germination guide for best results
London FAQ
When should I start seeds in London?
Start seeds indoors by early April under lights. This gives your plants 4-6 weeks of indoor vegetative growth before transplanting outdoors around late May. If you are growing autoflowering seeds, you can start them indoors any time of year for year-round harvests. The key mistake we see: starting too late and losing finishing time at the end of the season. In London, every week of head start matters because September moisture — London gets more precipitation than Toronto in early fall can end the outdoor season abruptly.
Can cannabis finish outdoors in London?
Yes. London's 150-165 frost-free days give you enough time for fast-finishing photoperiod strains and plenty of time for autoflowers. The challenge is not season length — it is lake-effect moisture from both Lake Huron and Lake Erie. Choose strains that handle moderate to high (65-80%) humidity and plan to harvest during the late September to early October window.
What strains handle London's humidity?
Mold-resistant strains with open bud structures are essential in London's moderate to high (65-80%) humidity. White Widow handles moisture better than dense indicas. Northern Lights Auto finishes fast enough to harvest before the worst humidity period. Avoid compact, rock-hard bud structures — they trap moisture and rot from the inside.
Is indoor or outdoor growing better in London?
outdoor growing with humidity-aware strain selection, indoor through winter. Indoor growing in London gives you full environmental control and year-round production. The ambient humidity means you will need a dehumidifier during flowering. Outdoor growing works as a summer supplement with fast strains.
How fast does delivery to London take?
Most orders arrive within 2-4 business days. London is a major Ontario city, so delivery times are consistent. All orders include tracking and ship in plain, unmarked packaging via Canada Post.
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