When to Plant Sunflowers 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 sunflowers in London from late may through early june (after victoria day)..
Sunflowers Planting Window for London, ON
Direct sow sunflower seeds after last frost when soil reaches 10°C / 50°F. Most zones: April–June. Warm-season annual — does not tolerate frost. Days to bloom: 70–100 days from seed.
For London, ON specifically, the recommended planting window is Late May through early June (after 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.
Sunflowers are tender annuals — frost kills them at any age. Direct sow only after last frost when soil reaches 10°C.
Best Sunflowers 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.
Tall (3 m) classic giant sunflower. 90 days to bloom — works in southern Ontario and BC; tight for Calgary/Edmonton.
Branching habit, 1.5 m tall, multiple golden-yellow blooms. 60 days. Excellent for short-season Prairies.
Cut-flower industry standard. 50-60 days. Successive sowings every 2 weeks for continuous Canadian blooms.
Branching pale yellow. 1.5-2 m tall. 90 days. Excellent for pollinators in Ontario and Quebec gardens.
60 cm container-friendly fully-double yellow blooms. 60 days. Works on Prairie balconies.
How to Plant Sunflowers in London
Sow method: direct sow after last frost. The steps below adapt the general planting advice for London, ON's climate and timing.
- →Direct sow sunflower seeds 2.5 cm (1 inch) deep, after the last frost when soil reaches 10°C (50°F).
- →Space giant varieties 60 cm (24 inches) apart; branching types 30 cm (12 inches); dwarf 20 cm (8 inches).
- →Choose a site with full sun (8+ hours) — sunflowers track the sun and lean toward shade.
- →Water consistently for the first 3 weeks; once established, water deeply weekly during dry periods.
- →Stake giant varieties at planting — adding stakes after the plant reaches 1 m (3 ft) damages roots.
- →Sidedress with balanced fertilizer when plants reach 60 cm (2 ft) tall — once is enough.
Frequently Asked Questions about Sunflowers in London, ON
When can I plant sunflowers in London?
Plant sunflowers in London from late may through early june (after 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 sunflowers winter-hardy in London?
Sunflowers are tender annuals — frost kills them at any age. Direct sow only after last frost when soil reaches 10°C.