USDA Hardiness Zone 9B Growing Guide
Source: USDA Agricultural Research Service Plant Hardiness Zone Map 2023
South Florida and San Diego — near-tropical conditions.
Where Zone 9B sits on the national map
Zone Position
Key Facts — Zone 9B
- Avg. coldest night: 25°F to 30°F (-3.9°C to -1.1°C) — the band of average annual extreme minimum temperatures that defines this zone (USDA ARS PHZM 2023)
- What that means: in an average year your coldest night lands somewhere in that 5°F window. Actual lows can drop colder in extreme winters; daytime highs are not bounded by this number.
- Found In: 13 US states, including California, Texas, Florida and 10 more
- Growing Considerations: South Florida and San Diego — near-tropical conditions.
What Is Zone 9B?
USDA Hardiness Zone 9B is defined by an average annual extreme minimum temperature between 25°F and 30°F (-3.9°C to -1.1°C), according to the USDA ARS Plant Hardiness Zone Map 2023.
Coldest avg. low
25°F
USDA PHZM 2023
Warmest avg. low
30°F
USDA PHZM 2023
Coldest avg. low (°C)
-3.9°C
USDA PHZM 2023
States
13
Where Is Zone 9B Found?
Zone 9B appears across 13 states:
Plants That Thrive in Zone 9B
Plants well-adapted to the temperature range of this zone.
Mango (some varieties)
Grapefruit
Plumeria
Bird of Paradise
Your Zone Is Just One Factor
Zone 9B covers 81 counties across 6 states, and their growing seasons are not the same. Humboldt County, California measures 278 frost-free days a year; Maricopa County, Arizona measures 345 — a 67-day difference under the same winter low, before you get to soil drainage, summer heat, flood risk, or contamination proximity. Your Growable Ground report scores 1,112 plants against all of it for your specific address.
Measured across the 81 counties whose USDA PHZM centroid falls in Zone 9B — NOAA 1991–2020 Climate Normals, 28°F killing freeze. Median 325 days.
Your zone is a starting point — your parcel is the whole story
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Frequently Asked Questions
What plants grow in Zone 9B?
South Florida and San Diego — near-tropical conditions. Common plants that thrive include Mango (some varieties), Grapefruit, Plumeria, Bird of Paradise. Actual suitability depends on your parcel's soil, drainage, and microclimate.
What states have Zone 9B?
Zone 9B appears across 13 US states: California, Texas, Florida, Georgia, Oregon, Washington, Alabama, Arizona, Hawaii, Louisiana, Mississippi, Nevada, South Carolina.
What temperature is USDA Zone 9B?
USDA Hardiness Zone 9B is defined by an average annual extreme minimum temperature between 25°F and 30°F (-3.9°C to -1.1°C), per the USDA ARS Plant Hardiness Zone Map 2023.