When to Plant Sunflowers in Ontario – 2026
Published: April 27, 2026
Ontario spans Canadian hardiness zones across multiple cities. Plant sunflowers in Ontario from late may through early june (after victoria day).. Victoria Day weekend is the standard sunflower direct-sowing date in southern Ontario and Quebec. Sowing earlier risks rot in cold wet soil; sowing later compresses the bloom window before late September frost.
Sunflowers Planting Window for Ontario
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 Ontario specifically, the recommended planting window is Late May through early June (after Victoria Day).. Ontario gardens across multiple climate zones — adjust based on your specific city. Victoria Day weekend is the standard sunflower direct-sowing date in southern Ontario and Quebec. Sowing earlier risks rot in cold wet soil; sowing later compresses the bloom window before late September frost.
Sunflowers are tender annuals — frost kills them at any age. Direct sow only after last frost when soil reaches 10°C.
Ontario Cities — Sunflowers Planting Dates
Each city below has local frost dates, Canadian zone, and a city-specific sunflowers planting calendar.
Best Sunflowers Varieties for Ontario
For Ontario , 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.
Caring for Sunflowers in Ontario
Sow method: direct sow after last frost. The steps below adapt the general planting advice for Ontario'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 Ontario
When should I plant sunflowers in Ontario?
Plant sunflowers in Ontario from late may through early june (after victoria day).. 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.
What Canadian zones are in Ontario?
Ontario spans multiple Canadian hardiness zones depending on location. Major cities and their zones: Toronto (Zone 6b), Ottawa (Zone 5b), Hamilton (Zone 6b), London (Zone 6a), Kitchener (Zone 6a). Check planthardiness.gc.ca for your exact postal code.
What sunflowers varieties grow best in Ontario?
Mongolian Giant (Mammoth) (All Canadian zones): Tall (3 m) classic giant sunflower. 90 days to bloom — works in southern Ontario and BC; tight for Calgary/Edmonton. Soraya (All Canadian zones): Branching habit, 1.5 m tall, multiple golden-yellow blooms. 60 days. Excellent for short-season Prairies.