When to Plant Tomatoes in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
The most popular home garden vegetable in the US. Timing is everything — plant too early and frost kills seedlings; plant too late and summer heat stops fruit set.
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.
Tomatoes Planting Calendar for London
Start seeds indoors: March 22–29
Transplant outdoors: May 17–27
Harvest window: July 16 – August 10
Minimum soil temperature: 16°C (60°F)
Days to harvest: 60–85 days
Sun requirement: Full sun (8+ hours)
Fall crop planting: July 28–August 7 (harvest September 26)
⚠ Warm-climate gardeners (TX, FL, AZ) can grow TWO crops: spring (Feb–March transplant) and fall (July transplant for October harvest).
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 Tomatoes
- Bury the stem 2/3 deep when transplanting — roots grow from the buried stem for a stronger plant.
- Consistent watering prevents blossom end rot and fruit cracking; uneven moisture causes both.
- Stop heavy nitrogen once flowers appear — it causes leafy plants with few tomatoes.
- In heat climates, plant a fall crop in July — it avoids peak heat and produces into November.
Companion Planting in London
Pair tomato with Basil, Marigold, Carrot, Parsley for mutual benefit. Avoid planting near Potato, Fennel, Mature Dill, which compete with or inhibit tomato growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on tomatoes in London comes from Tomato Hornworm, Aphids, Early Blight, Blossom End Rot. 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 tomato in London?
London's last spring frost is around May 3. Start seeds indoors March 22–29. Transplant outdoors May 17–27.
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 tomato crop (60–85 days to maturity) before the first fall frost.
Can I grow tomato 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. For a fall tomato crop, plant around July 28–August 7 so plants mature before the first killing frost.