When to plant celery 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 celery 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
Feb 15 – Mar 1Sow 10–12 weeks before the set-out window opens (UNH: time from seed to transplant 10–12 weeks). Anchored to the median last spring freeze (May 10). University of New Hampshire Extension
Transplant outdoors
May 10 – May 24UNH: set out after the last frost. Purdue's semi-hardy class allows 2–4 weeks before; the later UNH rule is used (celery is easily vernalized by cold spells). Anchored to the median last spring freeze (May 10). University of New Hampshire Extension · Purdue University Extension
Variety assumption: A long, steady season (about 100–120 days from transplant; Penn State lists 120).
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 (2)
- University of New Hampshire Extension: Growing Vegetables: When to Plant Your Vegetable Garden [fact sheet] (accessed 2026-07-24)Per-crop 'time from seed to transplant' and 'safe to set out in garden' relative to last frost.
- Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.