When to Plant Sunflowers in Ottawa, ON – 2026
Published: April 27, 2026
Ottawa is in Canadian Zone 5b (continental inland). Last spring frost averages May 6; first fall frost October 6; the growing season runs about 153 frost-free days. Plant sunflowers in Ottawa from late may through early june (after victoria day)..
Sunflowers Planting Window for Ottawa, 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 Ottawa, ON specifically, the recommended planting window is Late May through early June (after Victoria Day).. Ottawa Valley winters are harsh. Choose short-season tomato varieties under 70 days (Stupice, Sunrise, Sub-Arctic Plenty) and transplant only after the May long weekend. Fall garden extends the productive season into October with cold-tolerant greens and brassicas.
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 Ottawa, ON
For Ottawa, ON (Canadian Zone 5b), 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 Ottawa
Sow method: direct sow after last frost. The steps below adapt the general planting advice for Ottawa, 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 Ottawa, ON
When can I plant sunflowers in Ottawa?
Plant sunflowers in Ottawa from late may through early june (after victoria day). based on the city's Canadian Zone 5b. Last spring frost: May 6; first fall frost: October 6; frost-free growing season: 153 days.
What Canadian zone is Ottawa?
Ottawa is in Canadian Zone 5b (USDA equivalent 5a). The climate is continental inland. Ottawa Valley winters are harsh. Choose short-season tomato varieties under 70 days (Stupice, Sunrise, Sub-Arctic Plenty) and transplant only after the May long weekend. Fall garden extends the productive season into October with cold-tolerant greens and brassicas.
Are sunflowers winter-hardy in Ottawa?
Sunflowers are tender annuals — frost kills them at any age. Direct sow only after last frost when soil reaches 10°C.