What zone 11b means
In zone 11b, the average of the coldest night of each winter (1991 to 2020) is 45 to 50°F (7 to 10°C). Some winters will be colder than that and some milder: the zone is an average, not the coldest temperature ever recorded. When a plant tag lists a zone range that includes 11b, the plant should survive a typical winter here. If you are in the "a" half, you are in the colder part of the zone.
Zone 11b next to its neighbors
Zone 11a, one half zone colder, averages 40 to 45°F (4 to 7°C). Zone 12a, one half zone warmer, averages 50 to 55°F (10 to 13°C). On the 2023 map, about half the country moved to the next warmer half zone compared with 2012, so some gardens that were in 11a are now in 11b.
Using zone 11b when you shop
Look for the hardiness range on plant tags and in catalogs. A plant listed for "zones 9 to 13" includes zone 11b. If the range stops just above you, choose a sheltered spot, mulch roots before winter or grow it in a pot. Remember that zones describe winter cold only; heat, rainfall and soil decide the rest. How to read a plant tag.
States with the most zone 11b ZIP codes
Frequently asked questions
What does zone 11b mean?
Zone 11b covers places where the average coldest winter night is 45 to 50°F (7 to 10°C). On the 2023 USDA map, 16 ZIP codes are in zone 11b.
What is the difference between zone 11a and 11b?
Each 10°F zone is split into two 5°F half zones. "a" is the colder half and "b" the warmer half. Zone 11a averages 40 to 45°F (4 to 7°C); zone 11b averages 45 to 50°F (7 to 10°C).
Source: 2023 USDA Plant Hardiness Zone Map ZIP code listings, PRISM Climate Group, Oregon State University; USDA ARS. Not the official USDA map.