When to plant snapdragon in Billings, Montana

April 12 – April 26

Transplant outdoors · typical Billings year

Climate 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 snapdragon 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.

Last spring freezeMay 101-in-10 after May 24

First fall freezeOctober 11-in-10 before Sep 19

Frost-free season≈ 142 daysmedian at 32°F

Hard freeze, 28°Apr 27 – Oct 12kills even hardy greens

USDA zone5a-20 to -15°F winter low — not frost timing

The Billings year

Start seeds indoorsMar 15 – Mar 29

Transplant outdoorsApr 12 – Apr 26

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 24

Snapdragon in Billings · freeze context from Billings Wtp, MT, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 15 – Mar 29

Colorado State's seed-starting table lists snapdragon at 8 weeks before the average frost-free date in the 'Indoors' column, the longest lead time of any source found, so indoor sowing opens 8 weeks before the median last freeze and runs a two-week span. Anchored to the median last spring freeze (May 10). Colorado State University Extension

Transplant outdoors

Apr 12 – Apr 26

Illinois Extension names snapdragon in its hardy-annual list and states those can usually be planted about four weeks before the frost-free date, and NC State agrees hardy annuals go out in spring before the last frost date, so transplanting opens 4 weeks before the median last freeze. Anchored to the median last spring freeze (May 10). NC State Extension

Variety assumption: Assumes ordinary bedding and cut-flower strains of Antirrhinum majus grown as an annual; it is a hardy annual that flowers best in cool weather and Colorado State's 8-week indoor lead time reflects its slow start from very fine seed.

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.

This week, not a typical year:

Crop rule sources (2)

Colorado State University Extension: Growing Annual Plants from Seed (accessed 2026-07-25)
"Table 1: Starting times for seeds grown indoors and in cold frames, shown as number of weeks to start seed before average frost-free date."
NC State Extension: Extension Gardener Handbook, Ch. 10: Herbaceous Ornamentals (accessed 2026-07-25)
"Hardy annuals are the most cold-tolerant. They tolerate light frost and some freezing weather without being killed. In most cases, hardy annuals are planted in the fall or in the spring before the last frost date."

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