When to Plant Marigolds 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 marigolds in Ottawa from after victoria day (may 18 to june 1)..

Marigolds Planting Window for Ottawa, ON

Direct sow marigolds after last frost or start indoors 6–8 weeks before last frost. One of the easiest annuals — germinates in 5–7 days, blooms in 6–8 weeks. Natural pest deterrent for vegetable gardens.

For Ottawa, ON specifically, the recommended planting window is After Victoria Day (May 18 to June 1).. 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.

Marigolds are tender annuals — all zones, all provinces. Frost kills them. Replant fresh seed or transplants every spring.

Best Marigolds 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.

French marigolds (Tagetes patula)All Canadian zones

25-40 cm tall, smaller flowers, longest bloom period. Best for Canadian borders and bedding.

African / American marigolds (T. erecta)All Canadian zones

Largest flowers (10 cm heads) on 60-90 cm plants. Best for back-of-border in Ontario, Quebec, and Atlantic Canada.

Signet marigolds (T. tenuifolia)All Canadian zones

Small daisy-like flowers, 30 cm mounding habit. Edible flowers with citrus scent.

Triploid hybrids (Mr. Majestic, Zenith)All Canadian zones

Sterile hybrids of French × African. Longest bloom period of any marigold — bloom continuously through Canadian summer.

Mexican marigold (Tagetes lucida)Zone 8 BC only

Perennial in BC's warmest microclimates. Used as anise-flavoured Mexican tarragon. Annual everywhere else in Canada.

How to Plant Marigolds in Ottawa

Sow method: direct sow or transplant. The steps below adapt the general planting advice for Ottawa, ON's climate and timing.

→Direct sow marigold seeds 0.5 cm (1/4 inch) deep, after last frost when soil reaches 12°C (55°F).
→For earliest blooms, start seeds indoors 6 to 8 weeks before last frost; transplant after frost.
→Space French marigolds 15 cm (6 inches) apart; African 30 cm (12 inches); Signet 20 cm (8 inches).
→Choose a site with full sun (6+ hours) — marigolds in shade get leggy and stop blooming.
→Water at the base; avoid overhead watering which causes powdery mildew on Old World marigolds.
→Deadhead spent blooms to extend the flowering period (skip for triploid hybrids — they self-clean).

Frequently Asked Questions about Marigolds in Ottawa, ON

When can I plant marigolds in Ottawa?

Plant marigolds in Ottawa from after victoria day (may 18 to june 1). 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 marigolds winter-hardy in Ottawa?