When to plant parsnips in St. Louis, Missouri

March 18 – April 1

Direct-sow 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. Direct-sow parsnips 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

Direct-sow outdoorsMar 18 – Apr 1

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

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

Every method, with its sources

Direct-sow outdoors

Mar 18 – Apr 1

Purdue: semi-hardy — 2–4 weeks before the last frost; Penn State's earliest sowing Apr 17 (−14 days) is the later start and is used. Parsnip seed germinates slowly in cold soil. Anchored to the median last spring freeze (Apr 1). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Start seeds indoors

Not calculated

Root crops are not transplanted; parsnips are direct-seeded with fresh seed.

Transplant outdoors

Not calculated

The cited extension guides do not time an outdoor transplanting window for this crop.

Fall planting

Not calculated

No source-backed fall planting rule exists for this crop in the registry, so no fall window is calculated.

Variety assumption: A long season (about 100–120 days; Penn State lists 110); flavor improves after fall frost.

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)

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.

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