PlantAlong

Hardiness zone

Zone 9a

The coldest winter night here averages 20 to 25°F1. Frost dates vary more than that suggests.

ZIP codes
2,199
Weather stations
432
Last reviewed
Photo: Alexander Aubin / Pexels
Your zone tells you how cold winter gets. It does not tell you when to plant.
Typical last frost
Mar 2most ZIPs Feb 16 – Mar 18
Typical first frost
Nov 26most ZIPs Nov 16 – Dec 9
Spread in spring
31 daysbetween early and late ZIPs
  1. Last spring frostmedian Mar 2
  2. First fall frostmedian Nov 26
  • Frost-free season (median)
Figure 1. When frosts fall across zone 9a: the full range (pale), most ZIP codes (10th to 90th percentile, solid) and the median (marker). From 432 NOAA stations matched to 1,671 ZIP codes.

Zone and frost date are different things. The zone comes from the coldest winter night; frost dates come from spring and fall temperatures at weather stations2. Your own dates can sit anywhere in the range above, so the calendar for your ZIP is the better guide.

Five digits. The calendar is computed on your device.

When to plant in zone 9a

Each crop uses its primary extension source, applied to this zone's frost spread. Rules written for another state are labelled with their source.

  1. Tomatoes
  2. Peppers
  3. Cucumbers
  4. Zucchini
  5. Beans
  6. Peas
  7. Lettuce
  8. Carrots
  9. Onions
  10. Garlic
  11. Potatoes
  12. BasilNo sourced window
  • 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 2. Planting windows across zone 9a. Solid and dashed bars: the window at the zone's median frost dates. Pale bars: where the same window falls across most of the zone's ZIP codes.
Table 1. Planting windows in zone 9a.
CropWhatZone medianAcross most of the zoneSource
TomatoesStart indoorsJan 6Dec 22 – Jan 22Oregon State, central OR3
Transplant outdoorsMar 16Mar 1 – Apr 1Colorado State4
Plant for fallAug 20 – Sep 3Aug 10 – Sep 16Texas A&M (E-502)5
PeppersStart indoorsJan 20Jan 5 – Feb 5Oregon State, central OR3
Transplant outdoorsMar 16Mar 1 – Apr 1Colorado State4
Plant for fallAug 6 – Sep 3Jul 27 – Sep 16Texas A&M (E-502)5
CucumbersStart indoorsFeb 17Feb 2 – Mar 4Oregon State, central OR3
Transplant outdoorsMar 9Feb 23 – Mar 25Oregon State, central OR3
Sow outdoorsMar 2Feb 16 – Mar 18Colorado State4
Plant for fallSep 3 – Sep 17Aug 24 – Sep 30Texas A&M (E-502)5
ZucchiniStart indoorsFeb 24Feb 9 – Mar 11Oregon State, central OR3
Transplant outdoorsMar 16Mar 1 – Apr 1Oregon State, central OR3
Sow outdoorsMar 2Feb 16 – Mar 18Colorado State4
Plant for fallAug 13 – Sep 3Aug 3 – Sep 16Texas A&M (E-502)5
BeansStart indoorsFeb 10Jan 26 – Feb 26Oregon State, central OR3
Transplant outdoorsMar 9Feb 23 – Mar 25Oregon State, central OR3
Sow outdoorsMar 2Feb 16 – Mar 18Colorado State4
Plant for fallSep 17 – Oct 1Sep 7 – Oct 14Texas A&M (E-502)5
Plant for fallAug 6 – Aug 20Jul 27 – Sep 2Texas A&M (E-502)5
PeasStart indoorsJan 6Dec 22 – Jan 22Oregon State, central OR3
Transplant outdoorsFeb 3Jan 19 – Feb 19Oregon State, central OR3
Sow outdoorsFeb 3 – Feb 17Jan 19 – Mar 4Colorado State4
Plant for fallSep 3 – Nov 12Aug 24 – Nov 25Texas A&M (E-502)5
LettuceStart indoorsJan 13Dec 29 – Jan 29Oregon State, central OR3
Transplant outdoorsFeb 17Feb 2 – Mar 4Oregon State, central OR3
Sow outdoorsFeb 3 – Feb 17Jan 19 – Mar 4Colorado State4
Plant for fallAug 20 – Sep 17Aug 10 – Sep 30Texas A&M (E-502)5
CarrotsSow outdoorsFeb 17 – Mar 2Feb 2 – Mar 18Colorado State4
Plant for fallAug 20 – Sep 3Aug 10 – Sep 16Texas A&M (E-502)5
OnionsStart indoorsNov 11Oct 27 – Nov 27Oregon State, central OR3
Transplant outdoorsJan 20Jan 5 – Feb 5Oregon State, central OR3
Sow outdoorsFeb 3 – Feb 17Jan 19 – Mar 4Colorado State4
Plant for fallSep 17 – Oct 1Sep 7 – Oct 14Texas A&M (E-502)5
GarlicPlant for fallDec 3 – Dec 10Nov 23 – Dec 23Wisconsin6
PotatoesSow outdoorsFeb 17 – Mar 2Feb 2 – Mar 18Colorado State4
Plant for fallAug 6 – Aug 20Jul 27 – Sep 2Texas A&M (E-502)5
BasilNo frost-relative rule is published; sources give conditions instead (see the crop page).

Sources

  1. PRISM Group, Oregon State University, 2023 USDA Plant Hardiness Zone Map ZIP code data (PHZM 2023), 2023-11-15. 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. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
  4. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 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.
  6. University of Wisconsin–Madison Division of Extension, Wisconsin Horticulture, Garlic, Allium sativum, Rev: 10/2023. Retrieved 2026-11-02.