When to plant cucumbers in St. Louis, Missouri

April 15 – April 29

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 cucumbers 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

Start seeds indoorsMar 18 – Mar 25

Transplant outdoorsApr 15 – Apr 29

Direct-sow outdoorsApr 15 – Apr 29

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

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

Every method, with its sources

Start seeds indoors

Mar 18 – Mar 25

Sow in individual pots 3–4 weeks before the outdoor window opens (UNH 3–4 weeks; Missouri G6570 3–5 weeks, sown directly in pots). Anchored to the median last spring freeze (Apr 1). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Apr 15 – Apr 29

UNH allows setting out 1–2 weeks after frost; Purdue's very-tender class (at least 2 weeks after) is the more conservative and is used. Anchored to the median last spring freeze (Apr 1). Purdue University Extension · University of New Hampshire Extension

Direct-sow outdoors

Apr 15 – Apr 29

Purdue: very tender — sow at least two weeks after the average last frost (UNH adds: when soil reaches 70°F). Penn State's earliest sowing (May 11 for a May 1 frost) is slightly earlier; the later Purdue rule is used. Anchored to the median last spring freeze (Apr 1). Purdue University Extension · Penn State Extension (York County Master Gardeners)

Variety assumption: Assumes an average slicing variety (about 55–70 days from seed; Penn State lists 70).

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 (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).
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.
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.

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