When Should You Plant Nasturtiums?
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GardenSays
Sow nasturtiums outside May 20 – May 30 — after frost danger passes and soil has warmed.
- Sow from
- May 20 – May 30
- Last frost (typ.)
- May 5
Nasturtiums are 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 20.
Do this this week
- 1.The main sowing window closed May 30
Calculated result · 3 verified sources · Checked 2026-07-18 · How we decide
Why
Sow through the warm months; nasturtiums 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
- UMN gives a Minnesota calendar window (indoors mid-late April, outdoors end of May); the outdoor figure is converted to a Minneapolis-relative estimate (last frost ~May 5). Blooms until the first hard frost. No specific in-row spacing distance found this round — plants range from ~12 in bush types to trailing types that need much more room, so no single figure is shown.
- 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 20 – May 30Calculated result
Nasturtium is frost-tender — sow only after frost danger passes AND soil has warmed (15-25 days after the last frost)
Data sources
- University of Minnesota Extension — Writers Guild Article: Nasturtiums — Nasturtiums can be started indoors in mid-to-late April or outdoors toward the end of May, and last until the first hard frost. A warm-season annual, full sun, thrives in poor soil. Bush types are around 12 inches tall; trailing types work well in pots, over walls, or on trellises. (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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