When to Plant Sweet Potatoes in Ottawa, ON
Published: April 24, 2026 · Updated: April 27, 2026
Tropical warm-season vining crop grown from rooted cuttings called slips. Needs 90–120 frost-free days and consistently warm soil — thrives in the South but grows as far north as Zone 5 with care.
Ottawa's Canadian Zone 5b (USDA 5a) continental climate brings cold winters, hot summers, and higher frost risk than Toronto thanks to the inland location. The 153 frost-free days from early May through early October is adequate for most vegetables, but variety selection — short-season cultivars under 70 days — matters significantly.
Sweet Potatoes Planting Calendar for Ottawa
Direct sow outdoors: May 27–June 6
Harvest window: August 25 – September 24
Minimum soil temperature: 16°C (60°F)
Days to harvest: 90–120 days
Sun requirement: Full sun (8+ hours)
⚠ Plant sweet potato slips 2–3 weeks after last frost when soil is consistently above 60°F. Needs 90–120 days of warm weather. Best in Zones 5–11.
Ottawa Climate Notes
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.
Growing Tips for Sweet Potatoes
- Order slips in early spring from a seed company; plant within 24 hours of arrival in pre-warmed soil.
- Form raised ridges or mounds 10 inches tall — sweet potatoes size up best in loose, warm, well-drained soil.
- Black plastic mulch warms soil quickly in northern climates and can add 2 weeks to the effective growing season.
- Harvest before the first fall frost — foliage damage signals the entire crop should come out of the ground quickly.
Companion Planting in Ottawa
Pair sweet potato with Bush Bean, Pea, Dill, Thyme for mutual benefit. Avoid planting near Squash, Tomato, Sunflower, which compete with or inhibit sweet potato growth.
Pests and Problems to Watch in Ottawa
The most common pest and disease pressure on sweet potatoes in Ottawa comes from Sweet Potato Weevil, Wireworm, Flea Beetle, Root Knot Nematode. Floating row covers through the first 4–6 weeks after planting block adult pests from laying eggs, and a weekly scouting routine catches infestations before they damage the crop.
Other Ontario Cities
Frequently Asked Questions
When do I plant sweet potato in Ottawa?
Ottawa's last spring frost is around May 6. Direct sow May 27–June 6.
What Canadian hardiness zone is Ottawa?
Ottawa is in Canadian Zone 5b (USDA equivalent 5a). The continental inland climate delivers 153 frost-free days from May 6 to October 6, which shapes every planting date in the local calendar.
How long is Ottawa's growing season?
Ottawa has 153 frost-free days — from May 6 in spring to October 6 in fall. That is more than enough time to finish a full sweet potato crop (90–120 days to maturity) before the first fall frost.
Can I grow sweet potato in containers in Ottawa?
Yes. Container growing on balconies and decks is practical in Ottawa — choose a 5-gallon or larger dark-coloured container to warm the root zone, use a high-quality potting mix, and water daily during hot summer weather. In milder climates, containers extend both spring and fall windows by several weeks.
What is the first fall frost in Ottawa?
Ottawa's average first fall frost is October 6. Most sweet potato in Ottawa is a single spring-timed planting designed to harvest before the first fall frost.