PlantAlong

When to plant peas in zone 5b

Transplant outdoors around Apr 3. That is 4 weeks before zone 5b's median last frost, May 11. Across most of zone 5b that date falls between Mar 24 and Apr 19.

Why a range: zone 5b is defined by winter lows, not frost dates. Its ZIP codes have median last frosts from Apr 21 to May 172, so a single zone date can be weeks off for you. The rule comes from Oregon State University Extension Service.

Last reviewed
Stations
687
ZIP codes
2,445
Photo: Mateusz Feliksik / 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. Peas in zone 5b. 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 68 weeks before last frost (Oregon State, central OR)
Transplant outdoors
Apr 3range Mar 24 – Apr 19

Five digits. The calendar is computed on your device.

What each source says, applied to zone 5b

The same frost dates give different answers depending on whose rule you follow. These are all the published rules we hold for peas, worked out at zone 5b's median frost dates.

Table 1. Peas rules from every source, at zone 5b's median last frost (May 1) and first frost (Oct 11).
SourceWhatRuleZone 5b median
Colorado State3Used aboveSow outdoors2-4 weeks before last frostApr 3 – Apr 17
Oregon State, central OR1Used aboveTransplant outdoors4 weeks before last frostApr 3
Oregon State, central OR1Used aboveStart indoors8 weeks before last frostMar 6
Texas A&M (E-502)4Sow outdoors2-8 weeks before last frostMar 6 – Apr 17
Texas A&M (E-502)4Plant for fall2-12 weeks before first frostJul 19 – Sep 27

Frost across zone 5b

  1. Last spring frostmedian May 1
  2. First fall frostmedian Oct 11
  • Frost-free season (median)
Figure 2. Frost dates across zone 5b, from 687 NOAA stations matched to 2,445 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. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.