When to Plant Potatoes in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
Cool-season root crop planted from seed potatoes 2–4 weeks before last frost. One of the easiest high-calorie staples to grow at home — one pound of seed potatoes yields 10 pounds of harvest.
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.
Potatoes Planting Calendar for London
Direct sow outdoors: April 12–22
Harvest window: June 21 – August 10
Minimum soil temperature: 7°C (45°F)
Days to harvest: 70–120 days
Sun requirement: Full sun (6+ hours)
⚠ Plant seed potatoes 2–4 weeks before last frost when soil is workable and above 45°F. Hill soil up around stems as plants grow. Needs well-drained, loose soil.
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 Potatoes
- Cut seed potatoes into 2-inch chunks with at least two eyes each, then let cut surfaces heal for 24–48 hours before planting.
- Plant 4 inches deep and 12 inches apart in loose, well-drained soil; add compost but avoid fresh manure.
- Hill up soil around stems when plants reach 6 inches tall to cover developing tubers and prevent green potatoes.
- Stop watering when foliage yellows; let skins toughen for 1–2 weeks before digging for better storage.
Companion Planting in London
Pair potato with Bean, Corn, Marigold, Horseradish for mutual benefit. Avoid planting near Tomato, Pepper, Cucumber, which compete with or inhibit potato growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on potatoes in London comes from Colorado Potato Beetle, Wireworm, Potato Scab, Late Blight. 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 potato in London?
London's last spring frost is around May 3. Direct sow April 12–22.
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 potato crop (70–120 days to maturity) before the first fall frost.
Can I grow potato 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 potato in London is a single spring-timed planting designed to harvest before the first fall frost.