🧭 Garden systemZones6 stepsFree working copy
Know your USDA zone: look it up once, use it every season
Quick answer
Type your zip code into the zone finder and write down three things: the zone (like 6b), its temperature band (-5 to 0°F for 6b) and the map it came from (USDA 2023). Then check each perennial's tag against it: your zone should sit inside the tag's range. For plants that spend winter in a pot outdoors, Illinois Extension says to pick ones that survive two zones colder.
Source: PRISM 2023 USDA hardiness zone GIS datasets and zip-code listing, checked October 6, 2026; USDA Plant Hardiness Zone Map (2023), checked October 6, 2026; Illinois Extension, overwintering potted plants, checked October 6, 2026.
Decide first
Do you need your zone?
Do it yourself
Look it up yourself
All it takes is a zip code and a minute. Do it before you buy any perennial, shrub, tree or bulb that has to live through winter outdoors.
Skip it
Skip it for one-season plants
If you only grow summer vegetables and annual flowers that die in fall anyway, the zone matters little. USDA calls its zone maps general guides for growing perennial plants. What you need instead are your frost dates.
Source: USDA ARS, how to use the zone maps, checked October 6, 2026.
Get help
Ask your county extension office
For a big purchase like a tree or a hedge, or a yard in a low spot, on a hill or by water, ask your county Cooperative Extension office or a local nursery what does well nearby. USDA says the map can't show microclimates that small.
Source: USDA ARS, how to use the zone maps, checked October 6, 2026.
- 10°Fper whole zoneUSDA Plant Hardiness Zone Map (2023), October 6, 2026
- 5°Fper half zone, a and bUSDA Plant Hardiness Zone Map (2023), October 6, 2026
- 40,502zip codes in the 2023 listingPRISM 2023 USDA hardiness zone GIS datasets and zip-code listing, October 6, 2026
- 2 zonescolder, for plants that winter in potsIllinois Extension, overwintering potted plants, October 6, 2026
Once now, then a few minutes each spring
The steps, in order
Look up your zone by zip code
Type your five-digit zip code into the zone finder. It reads the 2023 USDA zip code listing: 40,502 zip codes across the lower 48 states, Alaska, Hawaii and Puerto Rico. Zip code 43215, in Columbus, Ohio, comes back as zone 6b.
Have ready: Your zip code.
Source: PRISM 2023 USDA hardiness zone GIS datasets and zip-code listing, checked October 6, 2026.
Fill in the zone card
On the working copy, write the zone, its temperature band and the map year. Zone 6b means the average coldest winter night falls between -5°F and 0°F. The year matters: on the 2023 map, about half the country moved to the next warmer half zone.
Have ready: The working copy and a pen.
Source: USDA Plant Hardiness Zone Map (2023), checked October 6, 2026; USDA ARS news release, November 15, 2023, checked October 6, 2026.
Mark your cold and warm spots
Walk the yard on a cold morning. Low spots where frost hangs on, and open corners in the wind, run colder than the map. A bed against a sunny wall runs warmer. USDA's map is drawn on half-mile squares, so differences this small don't show up on it.
Have ready: A rough sketch of the yard on the back of the card.
Source: USDA ARS, how to use the zone maps, checked October 6, 2026.
Check each plant tag
A tag that says zones 4 to 8 means the plant should come through winters in zones 4 through 8. Your zone has to sit inside that range. In zone 6b, a zones 4 to 8 plant fits; a zones 7 to 10 plant is a gamble outdoors.
Have ready: The plant tags, or the plant names to look up.
Give potted plants two zones of margin
Roots in a pot sit in a small amount of soil that gets much colder than soil in the ground. Illinois Extension's rule: choose plants that survive two zones colder than where they'll grow. In zone 6, that means a tag that reaches zone 4.
Have ready: The tags of anything that winters in a pot.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
Log what made it through
In spring, note which plants came through and which didn't, on the plant hardiness log. After a few winters, your own record will tell you more about your yard than the map can.
Have ready: The plant hardiness log, printed from the zone finder.
Free, one page, black and white
Print the working copy
Zone card kit: the steps above as a checklist with a date box for each, on one US Letter page.
If a step gets skipped
What goes wrong
⚠️
Going by an old zone
Older tags, books and catalogs may use the 2012 map. About half the country moved to the next warmer half zone in 2023, so look up your zip code again rather than trusting memory.
Source: USDA ARS news release, November 15, 2023, checked October 6, 2026.
⚠️
Reading the zone as a planting date
The zone is a winter cold number. It says nothing about when the last spring frost or first fall frost comes, and USDA notes that plants grow best within a range of temperatures, hot as well as cold. Timing needs your frost dates.
Source: USDA ARS, how to use the zone maps, checked October 6, 2026.
⚠️
Wintering an edge-of-range plant in a pot
A plant rated right at your zone can live in the ground and die in a pot on the patio, because the little bit of soil in a pot gets much colder than garden soil.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
⚠️
Forgetting long cold spells
The zone comes from the average coldest night. USDA notes that many plants that survive a short cold snap may not tolerate longer stretches of cold.
Source: USDA ARS, how to use the zone maps, checked October 6, 2026.
When the steps change
Variants
🪴
Plants in the ground
Match the tag to your zone. A plant whose range ends right at your zone is at its edge, so give it your most sheltered spot.
🏙️
Pots that stay outside
Choose plants rated two zones colder than yours. Group the pots out of strong wind and sun, such as on the north or east side of a building, and mulch them heavily with straw, leaves or wood mulch.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
❄️
Pots you can bring in
An unheated garage, shed or cool basement works as a winter spot for potted perennials. Water them well before they go in and check on them through the winter.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
☀️
Alaska, Hawaii and Puerto Rico
The zone finder covers them too. The 2023 listing comes as four files, one each for the lower 48 states, Alaska, Hawaii and Puerto Rico.
Source: PRISM 2023 USDA hardiness zone GIS datasets and zip-code listing, checked October 6, 2026.
What people learn the second year
Tips and tricks
- Write the half zone. 6a and 6b are 5°F apart. Many tags give whole zones only, but the half zone tells you whether you sit at the cold or the warm end. (USDA Plant Hardiness Zone Map (2023))
- Photograph tags before they get lost. Keep a phone album of plant tags. When a plant struggles after winter, the tag's range is the first thing to check.
- For winter, read the low number. In a range like zones 4 to 9, the lower number is the one to compare with yours for winter cold.
- Look up the new zip code when you move. Neighboring zip codes can sit in different half zones. Look up the new one instead of assuming the town next door matches.
The one we checked the steps against
Primary source
How to Use the Maps, USDA Plant Hardiness Zone Map, USDA Agricultural Research Service. Checked October 6, 2026.
USDA's own page on how to use the Plant Hardiness Zone Map. It says the maps are general guides for growing perennial plants, built on average lowest temperatures, not the lowest ever; that microclimates can be too small to show on the map; and that wind, soil, moisture, humidity, snow and winter sunshine all change how plants come through winter.
The arithmetic and the background reading
Tools and guides in this system
- 🌡️ LookupUSDA zone finder by zip codeFind your 2023 USDA plant hardiness zone by zip code, see its winter low band in °F and °C, and check a plant tag's zone range against it.Open the tool
- 🗺️ SectionAll zones toolsFind your 2023 USDA hardiness zone and your NOAA frost dates by zip code, with a printable hardiness log and a frost date card.See the section
Common questions
Questions
What planting zone am I in?
Type your zip code into the zone finder. It returns your 2023 USDA hardiness zone and its temperature band, such as 6b at -5 to 0°F for zip code 43215.
Source: PRISM 2023 USDA hardiness zone GIS datasets and zip-code listing, checked October 6, 2026.
What does the zone range on a plant tag mean?
It's the range of zones where the plant is expected to survive winter outdoors. If your zone is inside the range, it fits. A zone 6b garden fits a plant tagged zones 4 to 8.
Why do potted plants need a colder zone rating?
The soil in a pot is a small amount, and it gets much colder than soil in the ground. Illinois Extension suggests choosing plants that survive two zones colder than where they will grow.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
Did my zone change in 2023?
It may have. USDA says about half the country moved to the next warmer half zone on the 2023 map. Look up your zip code again rather than relying on an old tag or catalog.
Source: USDA ARS news release, November 15, 2023, checked October 6, 2026.
Does my zone tell me when to plant?
No. The zone is a winter cold number. Planting dates come from your average last spring frost and first fall frost, which are a separate lookup.
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Sources
- 2023 USDA Plant Hardiness Zone GIS Datasets, PRISM Group, Oregon State University (for USDA). Checked October 6, 2026.
- 2023 USDA Plant Hardiness Zone Map, USDA Agricultural Research Service. Checked October 6, 2026.
- Overwintering potted plants, University of Illinois Extension, published November 27, 2024. Checked October 6, 2026.
- How to Use the Maps, USDA Plant Hardiness Zone Map, USDA Agricultural Research Service. Checked October 6, 2026.
- USDA Unveils Updated Plant Hardiness Zone Map, USDA Agricultural Research Service, published November 15, 2023. Checked October 6, 2026.
Planning guide, not a guarantee. See every source on the site on the sources page. Spotted an error? Tell us.