PlantAlong

When to plant beans in zone 6a

Transplant outdoors around May 5. That is 1 weeks after zone 6a's median last frost, Apr 281. Across most of zone 6a that date falls between Apr 23 and May 17.

Why a range: zone 6a is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Apr 16 to May 102, so a single zone date can be weeks off for you. The rule comes from Oregon State University Extension Service.

Last reviewed
Stations
924
ZIP codes
4,375
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 6a. 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
Apr 73 weeks before last frost (Oregon State, central OR)
Transplant outdoors
May 5range Apr 23 – May 17

Five digits. The calendar is computed on your device.

What each source says, applied to zone 6a

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 6a's median frost dates.

Table 1. Beans rules from every source, at zone 6a's median last frost (Apr 28) and first frost (Oct 17).
SourceWhatRuleZone 6a median
Colorado State3Used aboveSow outdoorsOn the last frostApr 28
Utah State4Sow outdoorsOn the last frostApr 28
Oregon State, central OR1Used aboveTransplant outdoors1 weeks after last frostMay 5
Oregon State, central OR1Used aboveStart indoors3 weeks before last frostApr 7
Texas A&M (E-502)5Sow outdoors1-4 weeks after last frostMay 5 – May 26
Texas A&M (E-502)5Plant for fall8-10 weeks before first frostAug 8 – Aug 22
Texas A&M (E-502)5Plant for fall14-16 weeks before first frostJun 27 – Jul 11

Frost across zone 6a

  1. Last spring frostmedian Apr 28
  2. First fall frostmedian Oct 17
  • Frost-free season (median)
Figure 2. Frost dates across zone 6a, from 924 NOAA stations matched to 4,375 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.