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Usda Hardiness Zone Lookup
ZIP önekine göre yaklaşık bölgesel özet. For precise zones, check the USDA Plant Hardiness Zone Map — microclimates, elevation, and urban heat islands can shift your zone by a half-step.
The USDA Plant Hardiness Zone Map divides North America into 13 zones — each a 10°F band of average annual extreme minimum temperature — with each zone split into A and B half-zones covering 5°F bands. Zone 1A is the coldest (average annual low of −60°F), Zone 13B is the warmest (average annual low of 65°F). The map was originally published in 1960, last comprehensively updated in 2023 using 1991–2020 weather data, and represents the single most-used reference for figuring out which perennials, shrubs, and trees will actually survive winter where you live.
A zone tells you cold-hardiness — which is half the planting puzzle. A plant rated “hardy to Zone 5” will survive winters down to roughly −20°F, the lower bound of Zone 5. That rating is based on the plant’s cold-tolerance physiology: ice-crystal tolerance in cells, ability to harden off in autumn, and ability to break dormancy in spring. If you live in Zone 6 and buy a Zone 7 plant, it’s rolling the dice every winter. If you buy Zone 4 in Zone 6, you’re fine — colder-rated plants do fine in warmer zones, assuming the warmer zone’s summer heat doesn’t exceed THEIR upper tolerance.
What zones do NOT tell you: heat tolerance (use the AHS Heat Zone Map for that), frost dates (separate from extreme-min temps), soil drainage, humidity, day length, or microclimate effects (a south-facing brick wall in Zone 5 can effectively be Zone 6). The zone is a useful first filter: if a plant fails the zone test, don’t even consider it for in-ground planting. If it passes, then check soil, sun, water, and microclimate before buying. This tool gives you the zone and temperature range from a ZIP code so the rest of your planting decisions can build on a correct foundation.
Nasıl Kullanılır
- Enter your 5-digit US ZIP code (or the closest one if you’re rural).
- Read your zone + half-zone (e.g., 6A) and the average annual extreme min temperature range.
- Cross-check against the plant tag or seed packet — a Zone 6 plant is fine in zones 6, 7, 8 etc. but risky in 5.
- Check microclimate factors before buying — south walls, urban heat islands, cold-air pockets can shift you a half-zone.
- Combine with first/last frost dates from the companion frost-date tool for full season planning.
Ne Zaman Kullanılır
- Picking perennials, shrubs, fruit trees — anything that needs to survive the winter outdoors.
- Reading plant tags or catalog descriptions that say “hardy to Zone X” and you don’t know your zone offhand.
- Comparing two plants with different zone ratings to see which is the safer bet.
- Planning a new garden in a town you just moved to — climate may be very different from your old zone.
Ne Zaman Kullanılmaz
- Selecting annuals — by definition they die at season’s end, so cold-hardiness rating doesn’t apply.
- Indoor or greenhouse plants — you control the environment; zone is irrelevant.
- Vegetable gardening (mostly) — vegetables care about frost dates and growing-degree days, not zones.
- Tropical or warm-climate horticulture (Hawaii, far south Florida) — you’re in Zone 11+ where cold isn’t the limiting factor and you should be looking at heat zones / rainfall instead.
Yaygın Kullanım Senaryoları
- Pre-decision sanity-check on inputs and outputs
- Educational use — demonstrating the underlying concept
- Onboarding a colleague who needs the same calculation/conversion
- Verifying a number or output before passing it on
Sık Sorulan Sorular
How do I find my exact zone if I’m on a zone boundary?
ZIP-code lookup gives the dominant zone for your ZIP. If you’re on a boundary (between Zone 6A and 6B, say) and you live at higher elevation or in a colder valley, treat yourself as the colder zone for planting decisions. The USDA’s interactive map at planthardiness.ars.usda.gov accepts addresses for finer-grained results.
Did the 2023 update shift my zone?
About half of the US shifted a half-zone warmer in the 2023 update versus the 2012 map, reflecting 1991-2020 climate-normal warming. If you’ve been gardening for 20+ years and your old maps say Zone 5B, you’re likely 6A now. Check the new map — some Zone 6 plants are now reasonably safe where Zone 6 used to be marginal.
What if my plant tag says “Zones 5-9”?
That’s a range — cold-hardy down to Zone 5 (about −20°F average annual low) and heat-tolerant up to Zone 9 (about 25°F average annual low — meaning still gets some chill). If you’re in Zone 4, the plant is too tender; in Zone 10 it’s likely too warm (might not get the chill hours it needs). You want your zone to fall inside the plant’s rated range.
Can I plant something one zone above my rating if I baby it?
Sometimes, with caveats. Microclimate (south-facing wall, urban heat island), winter mulch, burlap wrap, container gardening (bring inside), and snow cover (insulates roots) can buy you about a half-zone of effective warmth. A serial gardener can sometimes push a full zone with serious effort. But for low-maintenance landscapes, stick to your rated zone or colder.
Are USDA zones used outside the US?
Yes — Canada has its own Plant Hardiness Zone Map (similar concept, slightly different methodology), and European catalogs often cite USDA equivalents because the US system is well-known. The UK uses its own RHS hardiness rating (H1 to H7). When in doubt, convert via temperature: Zone 6 = roughly −20°F = roughly −29°C average annual minimum.
Why is heat zone different from cold zone?
Cold (USDA) zones gate winter survival — will it freeze to death. Heat (AHS) zones gate summer survival — will it cook, dehydrate, or fail to set fruit. A plant can be Zone 4 cold-hardy and Zone 7 heat-hardy, meaning it survives down to −30°F but can’t take more than ~30 days above 86°F. For a complete picture you need both.