PlantAlong

When to plant beans in zone 8a

Transplant outdoors around Apr 5. That is 1 weeks after zone 8a's median last frost, Mar 291. Across most of zone 8a that date falls between Mar 27 and Apr 14.

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
Stations
650
ZIP codes
2,528
Photo: Gobral / Pexels
These dates use the typical last frost for the whole zone. Your ZIP code gives a closer answer.
  1. Start indoorsOregon State, central OR
  2. Transplant outdoorsOregon State, central OR
  3. Sow outdoorsColorado 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. Beans 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
Mar 83 weeks before last frost (Oregon State, central OR)
Transplant outdoors
Apr 5range Mar 27 – Apr 14

Five digits. The calendar is computed on your device.

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 beans, worked out at zone 8a's median frost dates.

Table 1. Beans rules from every source, at zone 8a's median last frost (Mar 29) and first frost (Nov 6).
SourceWhatRuleZone 8a median
Colorado State3Used aboveSow outdoorsOn the last frostMar 29
Utah State4Sow outdoorsOn the last frostMar 29
Oregon State, central OR1Used aboveTransplant outdoors1 weeks after last frostApr 5
Oregon State, central OR1Used aboveStart indoors3 weeks before last frostMar 8
Texas A&M (E-502)5Sow outdoors1-4 weeks after last frostApr 5 – Apr 26
Texas A&M (E-502)5Plant for fall8-10 weeks before first frostAug 28 – Sep 11
Texas A&M (E-502)5Plant for fall14-16 weeks before first frostJul 17 – Jul 31

Frost across zone 8a

  1. Last spring frostmedian Mar 29
  2. First fall frostmedian Nov 6
  • Frost-free season (median)
Figure 2. Frost dates across zone 8a, from 650 NOAA stations matched to 2,528 ZIP codes.

Sources

  1. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
  2. NOAA National Centers for Environmental Information, U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), 2021. Retrieved 2026-11-02.
  3. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
  4. Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
  5. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.