“Planting zones are broken down into thirteen areas, also known as USDA zones, which cover the entire United States, including Hawaii, Alaska and Puerto Rico. Each agricultural zone covers a 10-degree range. Zone 1 is the coldest, with an average minimum winter temperature of -60 to -50 degrees F, while the minimum winter average temperature in Zone 13 is 60 to 70 degrees F.” (link here)
I’m a 10b — no, not shoe size! That’s the planting zone for Los Angeles:
Los Angeles County garden of garden designer and ceramicist Dustin Gimbel growing leucospermum, magnolia, acacia, gerbera, citrus
Planting Zone: 10b
With an average yearly temperature of 63.68°(F), Los Angeles has a Frost free growing season and is located in a warm temperate thorn steppe.* Common grasses include bermuda grass, buffalo grass, St. Augustine grass and zoysia grass.
Low Temp: 35 to 40°(F)
Sunny Days: 284
“The coast of California usually has dry, warm to hot summers, with rainy winters in the north and mild winters in the south. The high elevations of the Sierra Nevadas, Cascades and Klamath mountains have mild to moderate summer and snowy winters. The low elevation eastern deserts in Southern California see minimal frost in the winter and have hot summers, while higher elevation eastern deserts in the central part of the state are prone to thunderstorms from July through early September.”
Boyce Thompson Arboretum, Arizona
It’s a fun game. What’s the zone for Phoenix, you ask? Click on the state, and major cities will be highlighted. Phoenix is 9b. (“With an average yearly temperature of 75.05°(F), Phoenix has a February 26-November 20 growing season and is located in a subtropical desert scrub. Common grasses include bermuda grass and St. Augustine grass. Averages; Low Temp: 25 to 30°(F), Rainfall: 8.04” Sunny Days: 299, Altitude: 1093‘)
Tanglewild Gardens, Austin TX
Okay, I was just in Austin. Let’ check the deets on it: 8b ( “With an average yearly temperature of 69.4°(F), Austin has a February 17-December 6 growing season and is located in a subtropical dry forest. Common grasses include bermuda grass, buffalo grass, rye grass, St. Augustine grass and zoysia grass. Averages; Low Temp: 15 to 20°(F), Rainfall: 34.25” Sunny Days: 228, Altitude: 489′)
Go ahead, give it a try. Honolulu is 12a, Miami 11a...
"Instead of simply assuming you are in a certain zone and thinking you already know what grows best, click on the major metros near you to see detailed information specific to your exact area. Individual zones are no longer simply just bands that go across the country. Detailed sections are now based on multiple factors.
Click on your state to reveal a basic overview, including the state flower, a list of major metro areas, gardening zones and an overview of climate. By clicking your closest metro area, you’ll find even more detailed information to help make your gardening decisions."
Gilmour, which sells household/garden supplies, emailed this helpful planting zone map. No business relationship exists between Gilmour and AGO.
*that's my bold, since I was unfamiliar with this nomenclature "warm temperate thorn steppe," which derives from the Holdridge Life Zones Data Set.