When to plant lettuce in zone 8a

Transplant outdoors around Mar 15. That is 2 weeks before zone 8a's median last frost, Mar 291. Across most of zone 8a that date falls between Mar 6 and Mar 24.

Why a range: zone 8a is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Mar 20 to Apr 72, so a single zone date can be weeks off for you. The rule comes from Oregon State University Extension Service.

Last reviewed: 2026-11-02
Stations: 650
ZIP codes: 2,528

Photo: Zoran Milosavljevic / Pexels

These dates use the typical last frost for the whole zone. Your ZIP code gives a closer answer.

Start indoorsOregon State, central ORStart indoors across most of the zone: Jan 31 to Feb 18Start indoors at the zone median: Feb 9 (Oregon State, central OR)
Transplant outdoorsOregon State, central ORTransplant outdoors across most of the zone: Mar 6 to Mar 24Transplant outdoors at the zone median: Mar 15 (Oregon State, central OR)
Sow outdoorsColorado StateSow outdoors across most of the zone: Feb 21 to Mar 24Sow outdoors at the zone median: Mar 1 to Mar 15 (Colorado State)

Start indoors
Plant outdoors
Range across the zone
Frost-free season (median)
Spring frost risk (90% to 10%)
Fall frost risk (10% to 90%)

Figure 1. Lettuce in zone 8a. Dark bars: at the zone's median frost dates. Pale bars: across most of the zone's ZIP codes. Hatched blue: where the zone's last and first frosts fall.

Start seeds indoors: Feb 97 weeks before last frost (Oregon State, central OR)
Transplant outdoors: Mar 15range Mar 6 – Mar 24

What each source says, applied to zone 8a

The same frost dates give different answers depending on whose rule you follow. These are all the published rules we hold for lettuce, worked out at zone 8a's median frost dates.

Table 1. Lettuce rules from every source, at zone 8a's median last frost (Mar 29) and first frost (Nov 6).
Source	What	Rule	Zone 8a median
Colorado State3Used above	Sow outdoors	2-4 weeks before last frost	Mar 1 – Mar 15
Utah State4	Sow outdoors	2 weeks before last frost	Mar 15
Oregon State, central OR1Used above	Transplant outdoors	2 weeks before last frost	Mar 15
Oregon State, central OR1Used above	Start indoors	7 weeks before last frost	Feb 9
Texas A&M (E-502)5	Sow outdoors	From 6 wk before to 2 wk after last frost	Feb 16 – Apr 12
Texas A&M (E-502)5	Plant for fall	10-14 weeks before first frost	Jul 31 – Aug 28

Frost across zone 8a

Last spring frostmedian Mar 29Full range across the zone: Feb 28 to Jun 8Most of the zone (10th to 90th percentile): Mar 20 to Apr 7Zone median: Mar 29
First fall frostmedian Nov 6Full range across the zone: Sep 22 to Nov 26Most of the zone (10th to 90th percentile): Oct 31 to Nov 14Zone median: Nov 6

Frost-free season (median)

Figure 2. Frost dates across zone 8a, from 650 NOAA stations matched to 2,528 ZIP codes.

Planting lettuce with others

Cilantro Extension guidance Cilantro flowers attract aphid-eating beneficial insects (lacewings, lady beetles, parasitic wasps, spiders, syrphid flies) that reduce aphids on lettuce.6
Dill Extension guidance Dill flowers attract aphid-eating beneficial insects (lacewings, lady beetles, parasitic wasps, spiders, syrphid flies) that reduce aphids on lettuce.6
Fennel Extension guidance Fennel flowers attract aphid-eating beneficial insects (lacewings, lady beetles, parasitic wasps, spiders, syrphid flies) that reduce aphids on lettuce.6
Carrots Extension guidance Deep-taprooted carrots paired with shallow, wide-rooted lettuce use different soil layers, so their roots compete less.7 8 8

Sources

Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
NOAA National Centers for Environmental Information, U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), 2021. Retrieved 2026-11-02.
Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.
Penn State Extension, Herbs Make Good Plant Partners and Companions, Updated April 22, 2026. Retrieved 2026-11-02.
Washington State University Extension, Gardening with Companion Plants (Home Garden Series), EM128E, December 2023. Retrieved 2026-11-02.
University of California Agriculture and Natural Resources (UCCE Master Gardener Program), Companion Planting Chart: Companion planting in the vegetable garden, File dated 2023-09 in URL path; no date printed. Retrieved 2026-11-02.