What does a hardiness zone measure?

It measures the average annual extreme minimum temperature — how cold your coldest night usually gets in a typical year. That number is grouped into 10°F bands (each split into an a and b half), giving you a label like 8b or 10a.

How do I find my growing zone?

Enter your location in the Growmanac planner — it reads about a decade of your local daily lows and works out your zone automatically. It works anywhere in the world, not just the United States.

Guide

What is my growing zone? (and how to find yours)

Your growing zone — properly, a plant hardiness zone — is a simple label like 8b or 10a for how cold your winters typically get. It’s the single biggest clue to what you can grow outdoors, and when. Lower numbers mean colder winters; higher numbers, milder ones. The fastest way to find yours is to enter your location in the planner — but here’s what the number actually means.

What the number actually measures

A hardiness zone is built from one thing: the average annual extreme minimum temperature — how cold your coldest night gets in a typical year, averaged over many years. That range is sliced into 10°F bands and numbered. Each band is split in half: an “a” (the colder half) and a “b” (the warmer half). So “9b” is the milder end of zone 9, and “9a” the colder end.

It’s a winter-cold measure — nothing more. It doesn’t know about your summer heat, your rainfall, or how much sun your balcony gets. But because frost is what kills most tender plants, that one number tells you a surprising amount.

Hardy · cool-season — kale, spinach, peas, garlic — fine across most zones.
Tender · warm-season — tomato, basil, pepper — need a higher zone outdoors (or a sheltered balcony).

Your hardiness zone, in one picture: higher number = milder winter = more tender crops you can grow outdoors.

Why it decides what you can grow

Plants split roughly into two camps. Hardy, cool-season crops — kale, spinach, peas, garlic — shrug off cold and even prefer it. Tender, warm-season crops — tomatoes, basil, peppers, beans — die at the first frost. Your zone tells you whether a tender crop can live outdoors where you are, and roughly how long your frost-free window is. A higher zone means a longer season and more of the tender crops you can grow in the open ground.

Zones aren’t the whole story

Be honest with yourself here: your zone is a starting point, not a promise. Your own microclimate (a south-facing wall, a frost pocket at the bottom of a slope), your soil, your summer heat, and your day length all matter too. Treat the zone as the first filter — then let your own seasons teach you the rest.

How to find yours

You don’t need a map or a table. Open the planner, type your town, and it looks up about ten years of your local daily lows, takes each year’s coldest night, and averages them — that’s your zone. It works anywhere on Earth, and if you’re in the Southern hemisphere it flips the seasons for you.

Find your zone + what to plant now →

Educational guidance, not a guarantee. Growmanac makes no edibility or health claims — start small and treat your first season as an experiment.