PlantAlong

When to plant peppers in zone 5b

Transplant outdoors around May 15. That is 2 weeks after zone 5b's median last frost, May 11. Across most of zone 5b that date falls between May 5 and May 31.

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 Colorado State University Extension, written for CO and applied here to zone 5b's frost dates.

Last reviewed
Stations
687
ZIP codes
2,445
Photo: Yan Krukau / 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 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. Peppers 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 206 weeks before last frost (Oregon State, central OR)
Transplant outdoors
May 15range May 5 – May 31
First harvest, roughly
Jul 2470 days from transplant1

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 peppers, worked out at zone 5b's median frost dates.

Table 1. Peppers rules from every source, at zone 5b's median last frost (May 1) and first frost (Oct 11).
SourceWhatRuleZone 5b median
Colorado State1Used aboveTransplant outdoors2 weeks after last frostMay 15
Utah State3Transplant outdoors2 weeks after last frostMay 15
Oregon State, central OR4Transplant outdoors2 weeks after last frostMay 15
Oregon State, central OR4Used aboveStart indoors6 weeks before last frostMar 20
Texas A&M (E-502)5Transplant outdoors1-8 weeks after last frostMay 8 – Jun 26
Texas A&M (E-502)5Plant for fall12-16 weeks before first frostJun 21 – Jul 19

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. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 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. Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
  4. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. 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.