Your USDA plant hardiness zone is one of the most quoted numbers in gardening, printed on nearly every plant tag sold in the United States. This growing zone finder explains what yours actually means. Choose your zone and it shows the range of the coldest winter temperatures you can expect, a very rough guide to when spring frosts usually end in that zone, and which common perennial food plants and herbs are usually hardy there. It also explains what the zone does not tell you, which is just as important for planning a vegetable garden.
If you do not know your zone, the USDA publishes an official interactive Plant Hardiness Zone Map where you can look it up by ZIP code. Enter that zone here for a plain-language explanation.
How to use the growing zone finder
- Find your zone. Look up your ZIP code on the USDA Plant Hardiness Zone Map website, or check with your local Cooperative Extension office.
- Choose it in the finder, including the “a” or “b” half if you know it.
- Read the results: the winter low range, the approximate frost timing, and the perennials usually hardy in your zone.
- Use your local frost dates for planting. The frost date tool and planting calendar turn those dates into a schedule.
What a hardiness zone is
A hardiness zone describes the average coldest winter temperature at a location. The current USDA map, released in November 2023, is based on weather station data from 1991 to 2020. It divides the country into 13 zones by the average annual extreme minimum temperature: the coldest night of the year, averaged over 30 years.
Each zone covers a 10°F range, and each is split into two halves, “a” and “b”, of 5°F each. The “a” half is the colder of the two.
| Zone | Average coldest winter night | Examples of where it occurs |
|---|---|---|
| 3 | −40 to −30°F | Northern Minnesota and North Dakota |
| 4 | −30 to −20°F | Much of the upper Midwest and northern New England |
| 5 | −20 to −10°F | Parts of the Midwest, Great Plains and interior Northeast |
| 6 | −10 to 0°F | Much of the Ohio Valley, mid-Atlantic interior and Mountain West valleys |
| 7 | 0 to 10°F | Much of the upper South and coastal mid-Atlantic |
| 8 | 10 to 20°F | Much of the Southeast, Texas and the Pacific Northwest coast |
| 9 | 20 to 30°F | Gulf Coast, central Florida, much of California |
| 10 | 30 to 40°F | South Florida, coastal Southern California |
| 11–13 | 40°F and above | Hawaii, Puerto Rico and parts of the far south of Florida |
These examples are broad. Zones can change over short distances with elevation, nearby water and urban heat, so always check the map for your exact location.
Why the zone matters most for perennials
The main purpose of hardiness zones is to tell you which plants can survive your winters. When a plant tag says “hardy to zone 5”, it means the plant is expected to survive the typical coldest winter in zone 5 and warmer zones. It is most useful for plants that stay in the ground year after year: trees, shrubs, fruit, perennial flowers and perennial herbs and vegetables.
Common perennial food plants and their typical hardiness ranges include:
- Asparagus and rhubarb: very cold-hardy, usually from about zone 3 into zone 8. Both need a cold winter rest to produce well, which is why they struggle in the warmest zones.
- Chives and mint: tough and widely adaptable, usually from about zone 3 to zone 8 or 9.
- Strawberries: grown across most zones, with varieties suited to both cold and warm regions.
- Thyme, oregano and sage: usually hardy from about zone 5, given good drainage.
- Rosemary: usually reliably hardy only from about zone 7 or 8 southward, though some varieties are tougher. In colder zones it is often grown in a pot and brought indoors for winter.
- Figs and artichokes: generally perennial in milder zones, roughly zone 7 and warmer, with winter protection at the cold edge.
Hardiness varies by variety, so check the tag. Good drainage often matters as much as cold: many herbs that tolerate cold die in winter from sitting in wet soil.
What the zone does not tell you
This is where many gardeners go wrong. A hardiness zone describes only winter cold. It does not tell you:
- When to plant vegetables. That depends on your frost dates, which can differ by weeks between two places in the same zone.
- How hot your summers get. Zone 8 includes both the cool, cloudy Pacific Northwest coast and the hot, humid Southeast. Tomatoes behave very differently in each.
- How much rain you get. Zones say nothing about drought or humidity, which strongly affect what grows well.
- How long your growing season is. Season length comes from the time between the last spring frost and the first fall frost.
- Snow cover. Reliable snow insulates plant roots, so some perennials survive colder temperatures under snow than in bare, frozen ground.
For annual vegetables, which grow and die in one season, frost dates matter far more than the zone. Use the frost date tool to see your season length and planting windows.
Zones and frost dates: a rough relationship
Colder zones generally have later spring frosts and shorter seasons, and warmer zones earlier frosts and longer seasons. As a very rough guide, last spring frosts tend to fall around late May in zone 3, mid-May in zone 4, early to mid May in zone 5, mid to late April in zone 6, early to mid April in zone 7, and March in zone 8. In zones 9 and warmer, frost is occasional or rare.
Treat these as broad tendencies, not planting dates. Local factors such as elevation, valleys where cold air collects, and nearness to large lakes or the ocean can shift frost dates by several weeks. Your local Cooperative Extension office or a frost date lookup for your nearest weather station gives a far more reliable date.
Microclimates in your own garden
Even within a single yard, conditions vary. These small pockets with slightly different conditions are called microclimates, and they can effectively shift a spot half a zone warmer or colder.
- Warmer spots: beside south- and west-facing walls, near paving that stores heat, in sheltered corners, and in towns and cities, which hold heat at night.
- Colder spots: low areas where cold air pools on still nights, exposed hilltops, and north-facing slopes.
- Wind: exposed sites lose heat faster and dry out plants in winter. Fences, hedges and buildings provide shelter.
Gardeners use microclimates to grow plants at the edge of their hardiness, such as a rosemary planted against a warm, sunny wall a zone colder than it would normally survive.
Did my zone change?
Many gardeners found their zone shifted when the USDA released the updated map in 2023. Compared with the previous 2012 map, about half of the country moved into a warmer half zone. The USDA notes that some of the change reflects longer and more detailed records and improved mapping methods, not only changes in climate. Either way, the updated map is the best current guide. If your zone moved, plants that were borderline before may now be a reasonable choice, but a single unusually cold winter can still damage plants at the edge of their range.
Choosing plants by zone
- Read the tag or catalog listing for the zone range.
- Stay within your zone for long-lived plants, such as fruit trees and shrubs. Pushing the limit is fine for inexpensive perennials you are willing to replace.
- Consider the upper limit too. Some plants, including many fruit trees, asparagus and rhubarb, need a period of winter cold and may not do well in zones warmer than their range.
- Check local variety recommendations. Extension services publish lists of varieties proven in your region.
- Use containers for borderline plants, so they can be moved to shelter in winter.
For annual vegetables and herbs, the plant finder and plant database help you choose by sun, season and space instead.
Heat matters too
Hardiness zones measure cold, but summer heat limits many plants just as much. The American Horticultural Society publishes a separate Plant Heat Zone Map, which divides the country by the average number of days each year above 86°F, the temperature at which many plants begin to suffer heat stress. Some plant tags list both a hardiness zone and a heat zone.
Heat explains why plants rated for your hardiness zone can still struggle. Lettuce, spinach and peas bolt quickly in long, hot summers. Many perennials from cool climates decline in hot, humid regions even though winters there are mild. If you garden in a hot region, look for heat-tolerant varieties and make use of afternoon shade, which the sunlight requirement finder helps you plan.
Protecting borderline perennials in winter
If you grow a perennial at the cold edge of its range, a few precautions improve its chances:
- Plant in a sheltered spot, such as against a south-facing wall, away from cold, low ground.
- Mulch after the ground freezes. A few inches of straw or shredded leaves keeps soil temperature steady and prevents freeze-thaw cycles from heaving plants out of the ground.
- Improve drainage. Many plants survive cold but not cold combined with wet soil.
- Water before the ground freezes, especially evergreens, which lose moisture through their leaves in winter.
- Use containers for tender perennials such as rosemary in cold zones, and move them into an unheated garage or bright window for winter.
- Avoid late-season feeding, which encourages soft new growth that is easily damaged by early cold.
Frequently asked questions
How do I find my growing zone?
Use the USDA Plant Hardiness Zone Map website and enter your ZIP code, or ask your local Cooperative Extension office. Then choose that zone in the finder above for an explanation.
What does my hardiness zone mean?
It describes the average coldest winter temperature where you live, in 10-degree bands split into 5-degree halves. It tells you which perennial plants are likely to survive your winters.
Does my zone tell me when to plant vegetables?
Not directly. Planting times depend on your local frost dates, which can vary by weeks within the same zone. Use your frost dates to plan vegetable planting.
What is the difference between zone 7a and 7b?
Each zone spans 10°F and is split into halves. Zone 7a has an average coldest winter night of 0 to 5°F; zone 7b is slightly warmer, at 5 to 10°F.
Why did my growing zone change?
The USDA updated the map in 2023 using 1991–2020 data. Many areas shifted to a warmer half zone, partly because of more detailed data and mapping methods as well as changes in temperatures.
Can I grow plants outside my zone?
Sometimes. Warm microclimates, winter protection and containers let gardeners grow borderline plants, but long-lived plants such as fruit trees are safest within their rated zones.
What zone is best for a vegetable garden?
Vegetables grow in every zone. Because most are annuals, frost dates and summer heat matter more than the hardiness zone. Colder zones have shorter seasons; warmer zones may have two growing seasons.
What is a heat zone?
A heat zone, from the American Horticultural Society map, is based on the average number of days a year above 86°F. It helps explain why some plants struggle in hot climates even when winters are mild.
Are hardiness zones the same as growing zones?
Yes, in everyday use. When gardeners talk about their growing zone they almost always mean their USDA plant hardiness zone.
Can I grow tropical plants in zone 9 or 10?
Many subtropical plants grow outdoors in zones 9 and 10, though an occasional frost can still damage them. Check each plant’s rated zone and protect tender plants on cold nights.
Do hardiness zones apply to houseplants?
Not directly. Zones describe outdoor winter cold. They matter only if you move houseplants outdoors for summer, when they should come back inside before temperatures drop below what they tolerate.