When to Plant Sunflowers in New Hampshire
Few things bring more joy than a row of sunflowers turning their faces to the sun. Easy, dramatic, and pollinator-friendly.
The Short Answer
New Hampshire Frost Dates
Your planting dates depend on which part of New Hampshire you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern New Hampshire | 3b, 4a, 4b | May 20 - Jun 5 | Sep 10 - Sep 25 |
| Southern New Hampshire | 5a, 5b, 6a | May 1 - May 20 | Sep 25 - Oct 10 |
Sunflowers Planting Schedule for New Hampshire
Northern New Hampshire (Zones 3b, 4a, 4b)
Average last frost: May 20 - Jun 5 · Average first frost: Sep 10 - Sep 25
Southern New Hampshire (Zones 5a, 5b, 6a)
Average last frost: May 1 - May 20 · Average first frost: Sep 25 - Oct 10
Growing Sunflowers in New Hampshire
Sunflowers in New Hampshire's Climate
Sunflowers are surprisingly well-suited to cold climates — they grow fast enough to bloom before frost even in zones with 100-day seasons. Direct sow 1-2 weeks after your last frost. The intense summer daylight in northern latitudes actually produces taller stalks and larger heads. Choose varieties under 90 days to maturity for the shortest-season areas.
Soil Considerations for New Hampshire
Rocky, acidic New England soils. Glacial deposits. Granite bedrock. Raised beds essential in many areas. Make sure soil has warmed to at least 55°F before planting sunflowers outside.
New Hampshire Climate & Growing Season
Short growing season especially in north. Cold winters. Cool summers. Hardy varieties important. Sunflowers 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 New Hampshire: Northern New Hampshire (3b, 4a, 4b) has a last frost around May 20 - Jun 5, while Southern New Hampshire (5a, 5b, 6a) sees frost end around May 1 - May 20. This difference matters for sunflowers — transplant timing shifts by several weeks across the state.
Growing Tips
Direct sow is preferred — sunflowers don't love transplanting. Succession plant every 2 weeks for blooms all summer.
Companion Planting
Plant sunflowers alongside these companions for better growth:
Keep sunflowers away from:
The Bottom Line
Last reviewed: March 29, 2026