PlantAlong

When to plant peppers in zone 9a

Transplant outdoors around Mar 16. That is 2 weeks after zone 9a's median last frost, Mar 21. Across most of zone 9a that date falls between Mar 1 and Apr 1.

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 Colorado State University Extension, written for CO and applied here to zone 9a's frost dates.

Last reviewed
Stations
432
ZIP codes
1,671
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
  3. 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. Peppers 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
Jan 206 weeks before last frost (Oregon State, central OR)
Transplant outdoors
Mar 16range Mar 1 – Apr 1
First harvest, roughly
May 2570 days from transplant1
Fall planting
Aug 612-16 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 peppers, worked out at zone 9a's median frost dates.

Table 1. Peppers rules from every source, at zone 9a's median last frost (Mar 2) and first frost (Nov 26).
SourceWhatRuleZone 9a median
Colorado State1Used aboveTransplant outdoors2 weeks after last frostMar 16
Utah State3Transplant outdoors2 weeks after last frostMar 16
Oregon State, central OR4Transplant outdoors2 weeks after last frostMar 16
Oregon State, central OR4Used aboveStart indoors6 weeks before last frostJan 20
Texas A&M (E-502)5Transplant outdoors1-8 weeks after last frostMar 9 – Apr 27
Texas A&M (E-502)5Used abovePlant for fall12-16 weeks before first frostAug 6 – Sep 3

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. 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.