Your growing zone is the single most useful number in gardening. It tells you when your season starts and ends, how long it lasts, and which plants will actually survive where you live. Get it right and everything else gets easier.
Here is what a zone means, what to plant across the most common zones (3 through 10), and the things a zone number quietly leaves out.
The USDA hardiness zone system divides the country by average annual minimum temperature, in 10 degree bands. Your zone number is a shorthand for how cold your winters get, which in turn sets your frost dates, the length of your growing season, and whether a given plant behaves as a perennial (comes back every year) or an annual (one season and done) where you live.
Lower numbers are colder and have shorter seasons. Higher numbers are warmer and longer. A plant rated hardy to zone 5 will survive a zone 5 winter and everything milder, but may freeze out in zone 4.
You need two minutes and your zip code. The zone calculator gives you your exact zone, your a or b subzone, and your average first and last frost dates, which are the numbers you actually plant by.
Scroll to your zone. These are the broad strokes; your local frost dates fine-tune the timing.
The cold end. Your season is short, so lean on cold-hardy crops that mature fast and shrug off a light frost. Start heat-lovers like tomatoes and peppers indoors 6 to 8 weeks before your last frost, then transplant once the ground warms.
Season extenders earn their keep here: row covers, cold frames, and a sunny wall can add weeks on both ends and pull you through surprise cold snaps.
The sweet spot for variety. A moderate season opens the door to nearly everything: tomatoes, peppers, beans, squash, corn, cucumbers, herbs, and the full range of root vegetables.
Think in two windows. Plant cool crops (lettuce, peas, radish) in early spring, then follow with warm crops (tomatoes, beans, squash) once frost has passed and the soil warms up.
Long enough for two full growing seasons. Spring and fall plantings are both productive, so you can harvest well into autumn and start again the next spring with barely a gap.
Summer heat is the catch. It stalls and bolts cool crops, so time lettuce, peas, and spinach for early spring and again for late fall. Tomatoes and peppers, meanwhile, absolutely thrive.
You can grow something every month. Here the challenge flips: heat is the enemy, not cold. Summer is too hot for cool crops, so the prime growing season runs fall through spring, when everyone up north is shut down.
Warm-climate perennials open up too. Citrus, figs, and tropical herbs live for years rather than a single season, so it's worth planting for the long haul.
Each zone splits into an a and a b half, a 5 degree difference in minimum winter temperature. For vegetables, that mostly shifts your frost dates by a week or two, not which crops you can grow. Zone 7a and 7b plant the same tomatoes; 7a just starts a little later in spring and gets nipped a little earlier in fall.
If you want the exact line, the zone calculator gives you your precise subzone and frost dates, which is all the precision you need to plant by.
Your zone is the starting point, not the whole story. A few things it can't see:
Zone first, then layout. Find your exact zone and frost dates, then map out what goes where and when.
Start by finding your USDA hardiness zone with your zip code, then match crops to your season length and frost dates. Colder zones (3 to 4) favor fast, cold-hardy crops, moderate zones (5 to 6) grow almost anything, and warm zones (7 to 10) get two seasons or year-round growing. Your local frost dates set the exact timing.
Zone 7 has a long season of roughly 200 days and two productive planting windows. Tomatoes, peppers, okra, and beans thrive in the heat, while lettuce, peas, and spinach do best planted in early spring and again in fall to dodge the summer heat.
Zone 9 grows year-round, with fall through spring as the prime season since summer is often too hot for cool crops. Peppers, sweet potatoes, and winter greens do well, and warm-climate perennials like citrus, figs, and tropical herbs live for years.
Plant by your frost dates, not the calendar. Cool crops like peas and lettuce go in a few weeks before your last spring frost. Warm crops like tomatoes and beans wait until after it has passed and the soil has warmed. In fall, count back from your first frost to time the last planting.
Not really. The a/b split is a 5 degree difference in winter low that shifts your frost dates by a week or two. It fine-tunes timing rather than changing which vegetables you can grow, so 7a and 7b gardeners plant the same crops on slightly different dates.
Know your zone and ready to lay it out? Space it efficiently with square foot gardening, pair crops well using the companion planting chart, or dig into individual crops in the plant database.