When to Plant Annuals in London, ON – 2026
Published: April 27, 2026
London is in Canadian Zone 6a (southwestern Ontario temperate). Last spring frost averages May 3; first fall frost October 20; the growing season runs about 170 frost-free days. Plant annuals in London from cool-season 2-4 weeks before victoria day. warm-season after may 18 (victoria day)..
Annuals Planting Window for London, ON
Plant warm-season annuals (petunias, zinnias, impatiens, begonias) after last frost when soil reaches 15°C / 60°F. Cool-season annuals (pansies, snapdragons, alyssum) can be planted 2–4 weeks before last frost. Start from seed indoors 6–8 weeks before transplanting.
For London, ON specifically, the recommended planting window is Cool-season 2-4 weeks before Victoria Day. Warm-season after May 18 (Victoria Day).. 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.
Annuals complete their lifecycle in one Canadian growing season. Cool-season annuals (pansies, snapdragons, alyssum) tolerate frost down to -7°C. Warm-season annuals (petunias, zinnias, marigolds, impatiens) are killed by any frost.
Best Annuals Varieties for London, ON
For London, ON (Canadian Zone 6a), choose varieties rated for your zone or one zone colder for reliable winter survival. The Canadian-bred or tested varieties below perform well in Ontario conditions.
Self-cleaning, no deadheading needed. Continuous bloom from late spring through first fall frost. Ideal for Canadian summer hanging baskets.
Powdery mildew resistant. Direct sowing works on the Prairies once soil reaches 12°C. Heat-tolerant — excellent for Calgary and Saskatoon summers.
Most reliable Canadian annual. Tolerates the wide diurnal temperature range typical of Calgary and Edmonton summers.
Cool-season annual that tolerates light frost — can go out 2 weeks before Victoria Day. Often blooms into November in mild Canadian falls.
Cool-season annual that bloom strongly in cool Canadian springs and falls. Often winter over in Zone 7-8 BC. Annual elsewhere.
How to Plant Annuals in London
Sow method: transplant or direct. The steps below adapt the general planting advice for London, ON's climate and timing.
- →Warm-season annuals: plant after last frost when soil reaches 15°C (60°F).
- →Cool-season annuals: plant 2 to 4 weeks before last frost or in fall (Zone 7+) for spring or winter color.
- →For earliest blooms, start seeds indoors 6 to 8 weeks before last frost; transplant after frost.
- →Choose full sun for most annuals (zinnias, marigolds, petunias) and part shade for shade-loving types (impatiens, begonias).
- →Space according to mature size — typically 25 to 30 cm (10 to 12 inches) for most bedding annuals.
- →Water at the base; avoid overhead watering which promotes powdery mildew on zinnias.
Frequently Asked Questions about Annuals in London, ON
When can I plant annuals in London?
Plant annuals in London from cool-season 2-4 weeks before victoria day. warm-season after may 18 (victoria day). based on the city's Canadian Zone 6a. Last spring frost: May 3; first fall frost: October 20; frost-free growing season: 170 days.
What Canadian zone is London?
London is in Canadian Zone 6a (USDA equivalent 5b). The climate is southwestern ontario temperate. 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.
Are annuals winter-hardy in London?
Annuals complete their lifecycle in one Canadian growing season. Cool-season annuals (pansies, snapdragons, alyssum) tolerate frost down to -7°C. Warm-season annuals (petunias, zinnias, marigolds, impatiens) are killed by any frost.