When to plant cucumbers in zone 8b

Transplant outdoors around Mar 24. That is 1 weeks after zone 8b's median last frost, Mar 171. Across most of zone 8b that date falls between Mar 13 and Apr 8.

Why a range: zone 8b is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Mar 6 to Apr 12, 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: 652
ZIP codes: 2,535

Photo: Agung Sutrisno / 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 18Start indoors at the zone median: Mar 3 (Oregon State, central OR)
Transplant outdoorsOregon State, central ORTransplant outdoors across most of the zone: Mar 13 to Apr 8Transplant outdoors at the zone median: Mar 24 (Oregon State, central OR)
Sow outdoorsColorado StateSow outdoors across most of the zone: Mar 6 to Apr 1Sow outdoors at the zone median: Mar 17 (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. Cucumbers in zone 8b. 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 32 weeks before last frost (Oregon State, central OR)
Transplant outdoors: Mar 24range Mar 13 – Apr 8

What each source says, applied to zone 8b

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

Table 1. Cucumbers rules from every source, at zone 8b's median last frost (Mar 17) and first frost (Nov 13).
Source	What	Rule	Zone 8b median
Colorado State3Used above	Sow outdoors	On the last frost	Mar 17
Utah State4	Sow outdoors	On the last frost	Mar 17
Oregon State, central OR1Used above	Transplant outdoors	1 weeks after last frost	Mar 24
Oregon State, central OR1Used above	Start indoors	2 weeks before last frost	Mar 3
Texas A&M (E-502)5	Sow outdoors	1-6 weeks after last frost	Mar 24 – Apr 28
Texas A&M (E-502)5	Plant for fall	10-12 weeks before first frost	Aug 21 – Sep 4

Frost across zone 8b

Last spring frostmedian Mar 17Full range across the zone: Feb 11 to Jun 3Most of the zone (10th to 90th percentile): Mar 6 to Apr 1Zone median: Mar 17
First fall frostmedian Nov 13Full range across the zone: Sep 14 to Dec 13Most of the zone (10th to 90th percentile): Nov 4 to Nov 23Zone median: Nov 13

Frost-free season (median)

Figure 2. Frost dates across zone 8b, from 652 NOAA stations matched to 2,535 ZIP codes.

Planting cucumbers with others

Marigold Tested in a study Claimed: marigold root exudates suppress nematodes. Field tests intercropping cucumber and squash with French marigold found no consistent effect on soil nematodes.6 6 6 7 7
Blue Hubbard squash Tested in a study A border of Blue Hubbard squash, which striped cucumber beetles prefer, encircles the cucumbers; beetles concentrate on the border, which is then sprayed.8 8 8 9 9

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.
Journal of Nematology 25(4):666-673 (Society of Nematologists); FLVC journal host, Effects of Mixed Cropping on a Soil Nematode Community in Honduras, 1993. Retrieved 2026-11-02.
University of Florida, IFAS Extension (Entomology and Nematology Department), Marigolds (Tagetes spp.) for Nematode Management (ENY-056), reviewed Reviewed November 2019; page footer "Reviewed: 01/2024". Retrieved 2026-11-02.
University of Connecticut Cooperative Extension System (UConn IPM), Protecting Cucumbers From Beetles and Wilt With Perimeter Trap Cropping, reviewed Reviewed 2012. Retrieved 2026-11-02.
University of Vermont Extension, Vermont Vegetable and Berry Program, Perimeter Trap Cropping: A Novel Approach to Insect Pest Control, July 2004. Retrieved 2026-11-02.