When to Plant Sweet Potatoes in Maine
Not related to regular potatoes at all. Sweet potatoes need heat and a long growing season but reward with incredible harvests.
The Short Answer
Maine Frost Dates
Your planting dates depend on which part of Maine you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Maine | 3b, 4a, 4b | May 20 - Jun 5 | Sep 10 - Sep 25 |
| Central Maine | 4b, 5a | May 10 - May 25 | Sep 20 - Oct 5 |
| Southern/Coastal Maine | 5a, 5b, 6a | May 1 - May 15 | Sep 25 - Oct 15 |
Sweet Potatoes Planting Schedule for Maine
Northern Maine (Zones 3b, 4a, 4b)
Average last frost: May 20 - Jun 5 · Average first frost: Sep 10 - Sep 25
Central Maine (Zones 4b, 5a)
Average last frost: May 10 - May 25 · Average first frost: Sep 20 - Oct 5
Southern/Coastal Maine (Zones 5a, 5b, 6a)
Average last frost: May 1 - May 15 · Average first frost: Sep 25 - Oct 15
Growing Sweet Potatoes in Maine
Sweet Potatoes in Maine's Climate
Sweet potatoes are a stretch in cold climates — the crop needs 90+ days of warm soil and air. Southern zones 5b-5a gardeners can succeed with Beauregard (90 days), black plastic mulch, and raised beds. Northern zone 3-4 gardeners should skip sweet potatoes — the season simply isn't long enough. Container growing on a sun-baked patio sometimes works where in-ground doesn't.
Soil Considerations for Maine
Acidic, rocky soils. Blueberries thrive naturally. Raised beds common to deal with rocks. Amendment with lime needed for many vegetables. Loose, well-drained soil is especially important for sweet potatoes since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
Maine Climate & Growing Season
Short growing season but long summer days help. Maritime influence on coast. Season extension techniques very valuable. Sweet Potatoes cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Maine: Northern Maine (3b, 4a, 4b) has a last frost around May 20 - Jun 5, while Southern/Coastal Maine (5a, 5b, 6a) sees frost end around May 1 - May 15. This difference matters for sweet potatoes — transplant timing shifts by several weeks across the state.
Growing Tips
Grow from slips, not seeds. Start slips from a sweet potato in water 8 weeks before transplanting. Cure harvested tubers in warmth for 10 days.
Companion Planting
Plant sweet potatoes alongside these companions for better growth:
Keep sweet potatoes away from:
The Bottom Line
Last reviewed: March 29, 2026