When to Plant Pumpkins in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
Warm-season vining crop timed backward from desired harvest date. For Halloween pumpkins, plant late June to mid-July. Needs 75–100 frost-free days and plenty of space.
London's Canadian Zone 6a (USDA 5b) southwestern Ontario climate delivers adequate rainfall, warm summers, and 170 frost-free days. Shorter than Toronto's season but long enough for reliable production of most warm-season crops with appropriate variety selection.
Pumpkins Planting Calendar for London
Start seeds indoors: April 12–19
Transplant outdoors: May 10–20
Direct sow outdoors: May 10–20
Harvest window: July 24 – August 18
Minimum soil temperature: 16°C (60°F)
Days to harvest: 75–100 days
Sun requirement: Full sun (8+ hours)
⚠ Count back 75–100 days from desired harvest date. For Halloween harvest, plant late June to mid-July. Plant 1–2 weeks after last frost.
London Climate Notes
London has 150-170 frost-free days — adequate for most warm-season crops when transplants go in by late May. The region's rich soils support heavy feeders like tomatoes and brassicas with minimal amendment.
Growing Tips for Pumpkins
- For Halloween pumpkins, count back 75–100 days from October 31 — plant between late June and mid-July in most climates.
- Plant on hills or mounds to warm soil and improve drainage; two plants per hill is plenty.
- Rotate pumpkins away from squash, cucumber, and melon beds on a 3-year cycle to break disease cycles.
- Elevate developing pumpkins onto cardboard or straw to prevent rot from soil contact.
Companion Planting in London
Pair pumpkin with Corn, Bush Bean, Nasturtium, Marigold for mutual benefit. Avoid planting near Potato, Summer Squash, Zucchini, which compete with or inhibit pumpkin growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on pumpkins in London comes from Squash Vine Borer, Squash Bug, Cucumber Beetle, Powdery Mildew. Floating row covers through the first 4–6 weeks after planting block adult pests from laying eggs, and a weekly scouting routine catches infestations before they damage the crop.
Other Ontario Cities
Frequently Asked Questions
When do I plant pumpkin in London?
London's last spring frost is around May 3. Start seeds indoors April 12–19. Transplant outdoors May 10–20.
What Canadian hardiness zone is London?
London is in Canadian Zone 6a (USDA equivalent 5b). The southwestern Ontario temperate climate delivers 170 frost-free days from May 3 to October 20, which shapes every planting date in the local calendar.
How long is London's growing season?
London has 170 frost-free days — from May 3 in spring to October 20 in fall. That is more than enough time to finish a full pumpkin crop (75–100 days to maturity) before the first fall frost.
Can I grow pumpkin in containers in London?
Yes. Container growing on balconies and decks is practical in London — choose a 5-gallon or larger dark-coloured container to warm the root zone, use a high-quality potting mix, and water daily during hot summer weather. In milder climates, containers extend both spring and fall windows by several weeks.
What is the first fall frost in London?
London's average first fall frost is October 20. Most pumpkin in London is a single spring-timed planting designed to harvest before the first fall frost.