USDA Planting Zones Guide: Growing Zones by State Across the United States

USDA planting zones, also called hardiness zones or garden zones, are based on the average annual extreme minimum winter temperature at a location over a 30-year period. The United States is divided into 13 zones, each covering a 10°F range, and each zone is split into “a” and “b” half-zones that differ by 5°F. These zones help gardeners predict whether a perennial plant is likely to survive winter in their climate.

The most accurate way to find your zone is to use the official USDA Plant Hardiness Zone Map and enter your ZIP code in the search box. The interactive map will zoom to your location and display the zone (including the a/b half-zone). You can also view downloadable state maps, or approximate your zone by comparing your location to nearby cities on the map.

The USDA map is updated occasionally when enough new climate data has accumulated. Major updates were released in 1990, 2012, and 2023. The 2023 version is based on 1991–2020 weather data and shows that about half of the United States has shifted at least a half-zone warmer compared with previous editions, reflecting a trend toward milder winter lows in many regions.

Your planting zone is about how cold it gets in winter and whether a perennial can survive those minimum temperatures. Frost dates and growing season describe when freezing temperatures start and end each year and how many frost-free days you get. Zones tell you what can live through winter; frost dates and season length tell you when to plant seeds and transplants. You need both pieces of information for smart garden planning

Sometimes, yes—but it usually takes more work. A plant that’s rated for warmer zones than yours may be grown as an annual, in a container you move indoors, or with extra winter protection like mulching and covers. Conversely, cold-hardy plants from lower zones can often handle warmer climates, but may dislike intense summer heat or lack of winter chill. The further you “stretch” beyond your zone, the more risk, care, and experimentation are involved.

USDA zones are most important for perennials, trees, and shrubs that must survive your coldest winter temperatures year after year. Annual vegetables and flowers only grow for one season, so they’re usually killed by frost regardless of zone. For annuals, frost dates, heat, and season length matter more than hardiness zone, though zone still hints at overall climate patterns.

A microclimate is a small area—like a sheltered courtyard, south-facing wall, raised bed, or low-lying frost pocket—where conditions are noticeably warmer or colder than the surrounding landscape. Microclimates can effectively make your garden behave about a half-zone warmer or cooler than the map suggests. That’s why two gardens in the same ZIP code can have different results with the exact same plant.

USDA planting zones measure cold tolerance based on the average annual minimum winter temperature. Heat zones, such as the American Horticultural Society (AHS) Heat Zone Map, measure how many days per year are hotter than 86°F (30°C), which affects heat stress in plants. “Climate zones” in building codes or other systems may use completely different criteria. For a full picture of what will thrive, gardeners often consult both hardiness zones (cold) and heat zones (heat).

No. A warmer zone on the new map doesn’t mean your existing plants are suddenly unsuitable. It reflects an updated average of past winter lows, not a guarantee that future winters will always be mild. If your current plants have been thriving, they’ll likely continue to do so. The new zone mainly gives you more options to consider when choosing new plants, especially marginally hardy ones.

Use your zone as a screening tool, not a rigid rule. When reading plant tags or catalogs, check that the plant is hardy to at least your zone number or a lower one (for example, hardy to Zones 4–8 if you’re in Zone 6). Then factor in sun, soil, moisture, heat, and frost dates. If you’re pushing the limits (trying something just outside your zone), start small, use protected spots, and be ready to experiment.

The USDA hardiness zone system is widely referenced in North America and sometimes adapted elsewhere, but many countries have their own maps and rating systems. Canada has a national plant hardiness map, the UK’s Royal Horticultural Society uses its own H1–H7 ratings, and other regions may publish local guidance. If you garden outside the U.S., it’s best to consult both USDA-equivalent zones and any local hardiness or climate resources.