When to Plant Annuals in Ontario – 2026
Published: April 27, 2026
Ontario spans Canadian hardiness zones across multiple cities. Plant annuals in Ontario from cool-season 2-4 weeks before victoria day. warm-season after may 18 (victoria day).. Victoria Day weekend (May 18, 2026) is the absolute standard for annual transplanting in Ontario and Quebec. The traditional wisdom — 'never plant before Victoria Day' — is based on actual frost-risk statistics and remains accurate. After Victoria Day, frost risk drops to under 10 percent in southern Ontario and Quebec.
Annuals Planting Window for Ontario
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 Ontario specifically, the recommended planting window is Cool-season 2-4 weeks before Victoria Day. Warm-season after May 18 (Victoria Day).. Ontario gardens across multiple climate zones — adjust based on your specific city. Victoria Day weekend (May 18, 2026) is the absolute standard for annual transplanting in Ontario and Quebec. The traditional wisdom — 'never plant before Victoria Day' — is based on actual frost-risk statistics and remains accurate. After Victoria Day, frost risk drops to under 10 percent in southern Ontario and Quebec.
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.
Ontario Cities — Annuals Planting Dates
Each city below has local frost dates, Canadian zone, and a city-specific annuals planting calendar.
Best Annuals 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.
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.
Caring for Annuals in Ontario
Sow method: transplant or direct. The steps below adapt the general planting advice for Ontario'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 Ontario
When should I plant annuals in Ontario?
Plant annuals in Ontario from cool-season 2-4 weeks before victoria day. warm-season after may 18 (victoria day).. 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.
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 annuals varieties grow best in Ontario?
Petunias (Wave series) (All Canadian zones): Self-cleaning, no deadheading needed. Continuous bloom from late spring through first fall frost. Ideal for Canadian summer hanging baskets. Zinnias (Profusion, Zahara) (All Canadian zones): Powdery mildew resistant. Direct sowing works on the Prairies once soil reaches 12°C. Heat-tolerant — excellent for Calgary and Saskatoon summers.