When to plant spinach in St. Louis, Missouri

February 18 – March 11

Transplant outdoors · typical St. Louis year

Climate 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 spinach 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.

Last spring freezeApril 11-in-10 after Apr 18

First fall freezeNovember 41-in-10 before Oct 24

Frost-free season≈ 218 daysmedian at 32°F

Hard freeze, 28°Mar 22 – Nov 15kills even hardy greens

USDA zone7a0 to 5°F winter low — not frost timing

The St. Louis year

Transplant outdoorsFeb 18 – Mar 11

Direct-sow outdoorsMar 2 – Mar 16

Fall plantingSep 9 – Oct 7

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 18

Spinach in St. Louis · freeze context from St Louis Sci Ctr, MO, 1991–2020 normals.

Every method, with its sources

Transplant outdoors

Feb 18 – Mar 11

UNH: safe to set out 3–6 weeks before the last frost. Anchored to the median last spring freeze (Apr 1). University of New Hampshire Extension

Direct-sow outdoors

Mar 2 – Mar 16

Purdue: hardy — 4–6 weeks before the last frost; Penn State's earliest sowing Apr 1 (−30 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 7

Purdue Table 2: plant fall spinach 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 an average savoy/smooth variety (about 40–50 days; Penn State lists 50).

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 (3)

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.
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.

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