When to plant nasturtium in Billings, Montana
May 10 – May 24
Transplant outdoors · typical Billings yearClimate basis: NOAA station Billings Wtp, MT (USC00240802), 13 mi (21 km) from downtown Billings (ZCTA 59101 centroid), elevation 3097 ft, on the 1991–2020 climate normals. Transplant nasturtium outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (May 10). One year in ten still freezes after May 24.
The Billings year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to May 24
Every method, with its sources
Start seeds indoors
Mar 29 – Apr 12UW-Madison states seed can be started indoors in peat pots 4 to 6 weeks before the last expected spring frost, giving 42 to 28 days before last frost. Anchored to the median last spring freeze (May 10). University of Wisconsin-Madison Division of Extension · University of Illinois Extension · Iowa State University Extension and Outreach · North Carolina Cooperative Extension, Pender County Center
Transplant outdoors
May 10 – May 24NC Cooperative Extension (Pender County) names nasturtium among the large-seeded plants to transplant outdoors after the threat of frost, giving a two-week set-out window from the last-frost date. Anchored to the median last spring freeze (May 10). University of Wisconsin-Madison Division of Extension · University of Illinois Extension · Iowa State University Extension and Outreach · North Carolina Cooperative Extension, Pender County Center
Direct-sow outdoors
May 10 – May 24Sources disagree - UW-Madison and Illinois Extension sow nasturtium only once all danger of frost has passed, while Iowa State treats it as a cool-season annual that can go in 3 to 4 weeks before the last frost - and the later, more frost-conservative after-frost window wins, opening at the last-frost date and running two weeks. Anchored to the median last spring freeze (May 10). Iowa State University Extension and Outreach
Variety assumption: Covers both climbing (T. majus) and bush (T. minus) garden nasturtiums; Illinois Extension notes nasturtium does not transplant well, so the transplant window assumes peat or paper pots planted intact, as UW-Madison specifies.
These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.
Crop rule sources (4)
- Iowa State University Extension and Outreach: Direct Seeding Vegetables and Annuals - Preparation and Care | Yard and Garden (accessed 2026-07-25)"Cool-season annuals, like viola and nasturtium, can be sown 3 to 4 weeks before the last frost."
- University of Wisconsin-Madison Division of Extension: Nasturtium, Tropaeolum species - Wisconsin Horticulture (accessed 2026-07-25)"Seed can be sown directly in the garden in late spring to early summer once all danger of frost has passed or started indoors in peat pots 4 to 6 weeks before the date of the last expected spring frost."
- University of Illinois Extension: Nasturtium | Herbs (accessed 2026-07-25)"Because nasturtium does not transplant well, it is suggested to directly sow seeds into the garden after danger of frost is past."
- North Carolina Cooperative Extension, Pender County Center: Growing Flowers and Vegetables From Seed (accessed 2026-07-25)"Large seeded flowers and vegetables are the easiest to grow and include cucumbers, zucchini, squash, melons, cosmos, marigolds, nasturtium, zinnias, and sunflowers. To get a head start on the season, seeds of these varieties can be sown indoors in mid-March to transplant outdoors after the threat of frost."