PlantAlong

When to plant beans in zone 9a

Transplant outdoors around Mar 9. That is 1 weeks after zone 9a's median last frost, Mar 21. Across most of zone 9a that date falls between Feb 23 and Mar 25.

Why a range: zone 9a is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Feb 16 to Mar 182, so a single zone date can be weeks off for you. The rule comes from Oregon State University Extension Service.

Last reviewed
Stations
432
ZIP codes
1,671
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
  4. Plant for fallTexas A&M (E-502)
  5. Plant for fallTexas A&M (E-502)
  • 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 9a. 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 103 weeks before last frost (Oregon State, central OR)
Transplant outdoors
Mar 9range Feb 23 – Mar 25
Fall planting
Sep 178-10 weeks before first frost

Five digits. The calendar is computed on your device.

What each source says, applied to zone 9a

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 9a's median frost dates.

Table 1. Beans rules from every source, at zone 9a's median last frost (Mar 2) and first frost (Nov 26).
SourceWhatRuleZone 9a median
Colorado State3Used aboveSow outdoorsOn the last frostMar 2
Utah State4Sow outdoorsOn the last frostMar 2
Oregon State, central OR1Used aboveTransplant outdoors1 weeks after last frostMar 9
Oregon State, central OR1Used aboveStart indoors3 weeks before last frostFeb 10
Texas A&M (E-502)5Sow outdoors1-4 weeks after last frostMar 9 – Mar 30
Texas A&M (E-502)5Used abovePlant for fall8-10 weeks before first frostSep 17 – Oct 1
Texas A&M (E-502)5Used abovePlant for fall14-16 weeks before first frostAug 6 – Aug 20

Frost across zone 9a

  1. Last spring frostmedian Mar 2
  2. First fall frostmedian Nov 26
  • Frost-free season (median)
Figure 2. Frost dates across zone 9a, from 432 NOAA stations matched to 1,671 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.