How to Grow Sweet Potatoes in Canada
How to grow sweet potatoes in Canada starts with a question most guides skip: whether the crop fits your season at all. Sweet Potatoes are requires over 3000 Corn Heat Units — mostly restricted to Region 2 (Southern Ontario) without heavy protection, so judge them against your frost dates rather than a simple day count. Transplant rooted slips late May/early June, once soil is warm. Give them full sun and space them 30-40 cm (12-16 in) apart, in raised hills to accelerate soil warming.
Do sweet potatoes fit your Canadian season?
Subtract days to maturity from your frost-free days. If the answer is not comfortably positive, the crop will not finish — no amount of good technique fixes an arithmetic problem.
| Season band | Frost-free days | Days to maturity | Does it fit? |
|---|---|---|---|
|
Long season Zones 7-9 |
150-222 frost-free days | Requires over 3000 Corn Heat Units — mostly restricted to Region 2 (Southern Ontario) without heavy protection | Overwintered or transplant-dependent — see the notes below. |
|
Medium season Zones 4-6 |
130-170 frost-free days | Requires over 3000 Corn Heat Units — mostly restricted to Region 2 (Southern Ontario) without heavy protection | Overwintered or transplant-dependent — see the notes below. |
|
Short season Zones 2-3 |
90-130 frost-free days | Requires over 3000 Corn Heat Units — mostly restricted to Region 2 (Southern Ontario) without heavy protection | Overwintered or transplant-dependent — see the notes below. |
When to plant sweet potatoes in Canada
Timing runs from your local last spring frost: roughly 28 March in Vancouver, around 20 April to 10 May in Toronto, 3 May in Montreal, 7 May in Edmonton and 23 May in Calgary. Transplant rooted slips late May/early June, once soil is warm.
Season extension for a short Canadian season
- Black plastic mulch laid two to three weeks before planting lifts soil temperature by several degrees — often the difference between a crop and a failure on the Prairies.
- Floating row cover adds roughly two to four weeks at each end of the season and keeps early pests off at the same time.
- Low tunnels and cold frames let hardy crops carry on well past the first frost, and let hardy sowings start earlier.
- Short-season cultivars are the cheapest form of season extension. Choosing one that matures two weeks earlier costs nothing and removes the risk entirely.
Soil and site
Loose, well-drained soil, pH 5.8-6.2. Highly sensitive to cold — chilling injury occurs below 10C.
Watering
Moderate, even watering during establishment.
Spacing and layout
Space sweet potatoes 30-40 cm (12-16 in) apart, in raised hills to accelerate soil warming. Crowding is the most common cause of disappointing yields — plants compete for light and water, and poor airflow between them raises disease pressure sharply.
Companion planting
Thyme, oregano.
Common problems
Marginal or unsuitable outside Region 2 without a greenhouse. Harvest immediately before or after the first fall frost; cure at 26-29C and 85-95% humidity for 3-7 days to heal wounds and sweeten. Store at 13-16C.
Cold spring soil is behind more Canadian failures than any pest. Seed sown below its germination minimum rots rather than sprouts, and a warm-season transplant set out into cold ground is stunted for the rest of the season even if it survives. Waiting a week is almost always cheaper than re-sowing.
Turn growing sweet potatoes into a written plan. The Canada Vegetable Garden Planner (printable PDF) has frost-date planning pages, bed layouts, crop rotation, a sowing log and a harvest tracker — 70 printable pages.
Frequently Asked Questions
Can I grow sweet potatoes in Canada?
This crop is either overwintered or grown from transplants, so judge it by your frost dates rather than a simple days-to-maturity count.
When should I plant sweet potatoes in Canada?
Transplant rooted slips late May/early June, once soil is warm. Work from your local last frost — around 28 March in Vancouver, 20 April to 10 May in Toronto, 3 May in Montreal and 23 May in Calgary.
How far apart should sweet potatoes be planted?
Space them 30-40 cm (12-16 in) apart, in raised hills to accelerate soil warming.
What usually goes wrong with sweet potatoes in Canada?
Marginal or unsuitable outside Region 2 without a greenhouse. Harvest immediately before or after the first fall frost; cure at 26-29C and 85-95% humidity for 3-7 days to heal wounds and sweeten. Store at 13-16C. Cold spring soil is the other common cause of failure — sowing before the soil has reached the crop's germination minimum causes seed to rot rather than sprout.
Last updated 25 August 2026
Tools That Help With This Crop
Use these links when the guide moves from reading into sowing, planting, watering, and keeping the crop healthy.
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.