When to plant lettuce in zone 6b

Transplant outdoors around Apr 8. That is 2 weeks before zone 6b's median last frost, Apr 221. Across most of zone 6b that date falls between Mar 27 and Apr 19.

Why a range: zone 6b is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Apr 10 to May 32, 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: 899
ZIP codes: 4,372

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: Feb 21 to Mar 15Start indoors at the zone median: Mar 4 (Oregon State, central OR)
Transplant outdoorsOregon State, central ORTransplant outdoors across most of the zone: Mar 27 to Apr 19Transplant outdoors at the zone median: Apr 8 (Oregon State, central OR)
Sow outdoorsColorado StateSow outdoors across most of the zone: Mar 13 to Apr 19Sow outdoors at the zone median: Mar 25 to Apr 8 (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 6b. 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: Mar 47 weeks before last frost (Oregon State, central OR)
Transplant outdoors: Apr 8range Mar 27 – Apr 19

What each source says, applied to zone 6b

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 6b's median frost dates.

Table 1. Lettuce rules from every source, at zone 6b's median last frost (Apr 22) and first frost (Oct 22).
Source	What	Rule	Zone 6b median
Colorado State3Used above	Sow outdoors	2-4 weeks before last frost	Mar 25 – Apr 8
Utah State4	Sow outdoors	2 weeks before last frost	Apr 8
Oregon State, central OR1Used above	Transplant outdoors	2 weeks before last frost	Apr 8
Oregon State, central OR1Used above	Start indoors	7 weeks before last frost	Mar 4
Texas A&M (E-502)5	Sow outdoors	From 6 wk before to 2 wk after last frost	Mar 11 – May 6
Texas A&M (E-502)5	Plant for fall	10-14 weeks before first frost	Jul 16 – Aug 13

Frost across zone 6b

Last spring frostmedian Apr 22Full range across the zone: Mar 31 to Jun 21Most of the zone (10th to 90th percentile): Apr 10 to May 3Zone median: Apr 22
First fall frostmedian Oct 22Full range across the zone: Sep 4 to Nov 12Most of the zone (10th to 90th percentile): Oct 10 to Oct 29Zone median: Oct 22

Frost-free season (median)

Figure 2. Frost dates across zone 6b, from 899 NOAA stations matched to 4,372 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.