When to plant lettuce in Boise, Idaho

April 19 – May 3

Transplant outdoors · typical Boise year

Climate basis: NOAA station Boise 7 N, ID (USC00101017), 6 mi (9 km) from downtown Boise (ZCTA 83702 centroid), elevation 3885 ft, on the 1991–2020 climate normals. Transplant lettuce outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (May 17). One year in ten still freezes after June 10.

Last spring freezeMay 171-in-10 after Jun 10

First fall freezeOctober 121-in-10 before Sep 27

Frost-free season≈ 147 daysmedian at 32°F

Hard freeze, 28°Apr 27 – Oct 24kills even hardy greens

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

The Boise year

Start seeds indoorsMar 15 – Mar 29

Transplant outdoorsApr 19 – May 3

Direct-sow outdoorsApr 26 – May 10

Fall plantingAug 17 – Sep 14

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

Lettuce in Boise · freeze context from Boise 7 N, ID, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 15 – Mar 29

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 (May 17). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Apr 19 – May 3

UNH: safe to set out 3–4 weeks before the last frost. Anchored to the median last spring freeze (May 17). University of New Hampshire Extension

Direct-sow outdoors

Apr 26 – May 10

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 (May 17). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Aug 17 – Sep 14

Purdue Table 2: plant fall lettuce at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 12). 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.

Keep exploring

This crop, other cities

Related crops in Boise

Local overview