When Should You Plant Sunflowers?
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GardenSays
Sow sunflowers outside May 5 – May 12 — after frost danger passes and soil has warmed.
- Sow from
- May 5 – May 12
- Last frost (typ.)
- May 5
Sunflowers are very frost-tender and germinate poorly in cold, wet ground — unlike peas or lettuce, you wait until AFTER the last frost (May 5) and until the soil warms. Sowing too early into cold spring soil rots the seed. The safe window in Minneapolis, MN opens around May 5.
Do this this week
- 1.The main sowing window closed May 12
Calculated result · 3 verified sources · Checked 2026-07-18 · How we decide
Why
Sow through the warm months; sunflowers stop producing once nights turn cold.
- Warm-season crops need warm soil to germinate: cold, wet spring ground causes seed rot and poor stands, which is why they go in after frost, not before.
- Days-to-maturity versus your frost-free season sets how late you can keep sowing.
When this doesn't apply
- Direct-seed after all danger of frost has passed; germinates in 7-10 days. Succession sowing keeps blooms coming all season.
- A cold snap after sowing can still kill seedlings — hold off if a late frost is forecast, even inside the window.
How this was calculated
- 1. Last spring frostMay 5Source guidance
Minneapolis, MN: typical (50% probability) last 32°F frost
- 2. First sowing windowMay 5 – May 12Calculated result
Sunflower is very frost-tender — sow only after frost danger passes AND soil has warmed (0-7 days after the last frost)
Data sources
- University of Minnesota Extension — Sunflowers — Direct seed sunflowers after all danger of frost has passed, 1 inch deep; germinate within 7-10 days. Water regularly 20 days before and after flowering to encourage root growth. Full sun; slightly acidic soil pH 6.0-6.8. (checked 2026-07-18)
- NOAA NCEI — 1991-2020 U.S. Climate Normals (freeze date probabilities) (checked 2026-07-15)
- National Gardening Association — frost date lookup (checked 2026-07-15)
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