When to Plant Kale in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
Frost-hardy leafy green that actually tastes better after a light frost. Plant 3–5 weeks before last frost for spring or late summer for fall and winter harvests.
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.
Kale Planting Calendar for London
Start seeds indoors: March 29–April 5
Transplant outdoors: April 5–15
Direct sow outdoors: April 5–15
Harvest window: May 30 – June 19
Minimum soil temperature: 4°C (40°F)
Days to harvest: 55–75 days
Sun requirement: Full sun to partial shade
Fall crop planting: August 25–September 4 (harvest October 19)
⚠ Plant kale 3–5 weeks before last frost for spring. Best planted in late summer (6–8 weeks before first fall frost) for fall/winter harvest. Frost sweetens the flavor.
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 Kale
- Harvest outer leaves first using the cut-and-come-again method; the central growing point will produce for months.
- Kale leaves become sweeter after the first frost as plants convert starches to sugars — wait for cold nights for best flavor.
- Use floating row covers to block cabbage white butterflies from laying eggs on plants.
- In Zones 6+, kale often overwinters in the garden and produces through early spring before bolting.
Companion Planting in London
Pair kale with Onion, Garlic, Beet, Celery for mutual benefit. Avoid planting near Tomato, Strawberry, Bean, which compete with or inhibit kale growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on kale in London comes from Cabbage Worm, Cabbage Looper, Aphid, Flea Beetle. 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 kale in London?
London's last spring frost is around May 3. Start seeds indoors March 29–April 5. Transplant outdoors April 5–15.
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 kale crop (55–75 days to maturity) before the first fall frost.
Can I grow kale 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 kale crop, plant around August 25–September 4 so plants mature before the first killing frost.