What zone 11a means
In zone 11a, the average of the coldest night of each winter (1991 to 2020) is 40 to 45°F (4 to 7°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 11a, 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 11a next to its neighbors
Zone 10b, one half zone colder, averages 35 to 40°F (2 to 4°C). Zone 11b, one half zone warmer, averages 45 to 50°F (7 to 10°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 10b are now in 11a.
Using zone 11a when you shop
Look for the hardiness range on plant tags and in catalogs. A plant listed for "zones 9 to 13" includes zone 11a. 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 11a ZIP codes
Cities in zone 11a
Frequently asked questions
What does zone 11a mean?
Zone 11a covers places where the average coldest winter night is 40 to 45°F (4 to 7°C). On the 2023 USDA map, 205 ZIP codes are in zone 11a.
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.