When to Plant Swiss Chard in London, ON
Published: April 24, 2026 · Updated: April 27, 2026
One of the most versatile vegetables — tolerates both cool and warm weather. Direct sow 2–4 weeks before last frost and harvest outer leaves continuously for months through summer.
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.
Swiss Chard Planting Calendar for London
Direct sow outdoors: April 12–22
Harvest window: June 1 – June 11
Minimum soil temperature: 4°C (40°F)
Days to harvest: 50–60 days
Sun requirement: Full sun to partial shade
Fall crop planting: August 25–September 4 (harvest October 14)
⚠ Direct sow Swiss chard 2–4 weeks before last frost. Tolerates both cool and warm weather — one of the most flexible vegetables in the garden. Harvest outer leaves continuously for months.
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 Swiss Chard
- Each chard 'seed' is a multi-seed cluster — thin to 8-inch spacing or transplant extras for full plants.
- Harvest outer stalks when they reach 8–10 inches; the plant produces continuously for 4–6 months.
- Chard tolerates part shade better than most leafy greens — good for shaded corners of the garden.
- In Zones 6+ Swiss chard often overwinters with light mulch and produces early spring leaves before bolting.
Companion Planting in London
Pair swiss chard with Bean, Onion, Cabbage, Kohlrabi for mutual benefit. Avoid planting near Cucumber, Melon, which compete with or inhibit swiss chard growth.
Pests and Problems to Watch in London
The most common pest and disease pressure on swiss chard in London comes from Leaf Miner, Aphid, Slug, 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 swiss chard 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 swiss chard crop (50–60 days to maturity) before the first fall frost.
Can I grow swiss chard 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 swiss chard crop, plant around August 25–September 4 so plants mature before the first killing frost.