When to plant lettuce in Detroit, Michigan

March 24 – April 7

Transplant outdoors · typical Detroit year

Climate basis: NOAA station Detroit City AP, MI (USW00014822), 6 mi (9 km) from downtown Detroit (ZCTA 48226 centroid), elevation 626 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 21). One year in ten still freezes after May 6.

Last spring freezeApril 211-in-10 after May 6

First fall freezeOctober 311-in-10 before Oct 17

Frost-free season≈ 190 daysmedian at 32°F

Hard freeze, 28°Apr 8 – Nov 9kills even hardy greens

USDA zone6b-5 to 0°F winter low — not frost timing

The Detroit year

Start seeds indoorsFeb 17 – Mar 3

Transplant outdoorsMar 24 – Apr 7

Direct-sow outdoorsMar 31 – Apr 14

Fall plantingSep 5 – Oct 3

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 6

Lettuce in Detroit · freeze context from Detroit City AP, MI, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 17 – Mar 3

Sow 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 21). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Mar 24 – Apr 7

UNH: safe to set out 3–4 weeks before the last frost. Anchored to the median last spring freeze (Apr 21). University of New Hampshire Extension

Direct-sow outdoors

Mar 31 – Apr 14

Purdue: 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 21). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Sep 5 – Oct 3

Purdue Table 2: plant fall lettuce at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 31). 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.

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).
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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