When to plant lettuce in St. Louis, Missouri
March 4 – March 18
Transplant outdoors · typical St. Louis yearClimate basis: NOAA station St Louis Sci Ctr, MO (USC00237452), 4 mi (7 km) from downtown St. Louis (ZCTA 63101 centroid), elevation 515 ft, on the 1991–2020 climate normals. Transplant lettuce outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 1). One year in ten still freezes after April 18.
The St. Louis year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 18
Every method, with its sources
Start seeds indoors
Jan 28 – Feb 11Sow 4–5 weeks before the set-out window opens (UNH 4–5 weeks; Missouri G6570 lists 6–8 weeks for head lettuce). Anchored to the median last spring freeze (Apr 1). University of New Hampshire Extension · University of Missouri Extension
Transplant outdoors
Mar 4 – Mar 18UNH: safe to set out 3–4 weeks before the last frost. Anchored to the median last spring freeze (Apr 1). University of New Hampshire Extension
Direct-sow outdoors
Mar 11 – Mar 25Purdue: semi-hardy — 2–4 weeks before the last frost; Penn State's earliest sowing Apr 10 (−21 days) is the later start and is used. Anchored to the median last spring freeze (Apr 1). Penn State Extension (York County Master Gardeners) · Purdue University Extension
Fall planting
Sep 9 – Oct 7Purdue Table 2: plant fall lettuce at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Nov 4). Purdue University Extension
Variety assumption: Assumes leaf lettuce (about 45–55 days; head types run longer).
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)
- 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.
- University of Missouri Extension: Starting Plants Indoors from Seeds (G6570) (accessed 2026-07-24)Weeks needed to grow vegetable transplants indoors (Table 2).
- Penn State Extension (York County Master Gardeners): Vegetable Seed Planting Guide (accessed 2026-07-24)Earliest/latest sowing dates for a May 1 last-frost / Oct 1 first-frost baseline; offsets derived by date difference from May 1. Also days-to-maturity figures.
- 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.