When to Plant Carrots in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
Carrots must be direct-sown — they cannot be transplanted without forking the root. Loose, rock-free soil at least 12 inches deep is essential for straight roots.
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.
Carrots Planting Calendar for London
Direct sow outdoors: April 5–15
Harvest window: June 14 – June 24
Minimum soil temperature: 7°C (45°F)
Days to harvest: 70–80 days
Sun requirement: Full sun
Fall crop planting: August 11–21 (harvest October 20)
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 Carrots
- Direct sow ONLY — transplanting carrots causes forked, misshapen roots every time.
- Soil must be loose and rock-free to at least 12 inches deep; raised beds are ideal.
- Thin to 3-inch spacing aggressively — crowded carrots fork and grow stunted.
- Light frost improves carrot sweetness — cold converts starches to sugar; fall carrots taste better than spring.
Companion Planting in London
Pair carrot with Tomato, Onion, Leek, Rosemary for mutual benefit. Avoid planting near Dill, Parsnip, Anise, which compete with or inhibit carrot growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on carrots in London comes from Carrot Fly, Wireworm, Leaf Blight, Forking from rocky soil. 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 carrot in London?
London's last spring frost is around May 3. Direct sow 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 carrot crop (70–80 days to maturity) before the first fall frost.
Can I grow carrot 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 carrot crop, plant around August 11–21 so plants mature before the first killing frost.