Our Guide to the USDA Gardening Zones

What Are Plant Hardiness Zones?

Plant hardiness zones are regions that have been labeled by their average minimum growing temperature. These zones help gardeners understand which plants will thrive in their zonal growing environment, say Jennifer and Adam O'Neal, owners of PepperHarrow Farm and co-authors of Small Farm, Big Dreams: Turning A Flower-Growing Passion into a Successful Floral Business.

The hardiness zones defined by the USDA begin with zone 1, which is the coldest and end with zone 13, which encompasses the warmest growing areas. "Remember that the lower number is colder and the larger number is warmer—that's a good mental trick to remember how they work," say the O'Neals.

Plant Hardiness Subzones

Each hardiness zone differs by 10 degrees Fahrenheit and is often split into two subzones, labeled "a" and "b," which differ by 5 degrees Fahrenheit. For example, zone 7's freezing range is between 0 and 10 degrees Fahrenheit. In Zone 7a, average freezing temperatures hit between 0 to 5 degrees Fahrenheit; 7b's range is between 5 and 10 degrees Fahrenheit. Understanding your subzone will ultimately help you make more precise decisions about your garden. To determine your subzone, first find your overarching zone on the USDA's map—then do a narrow location search with your zip code to find out whether you're "a" or "b."

Why It's Important to Know Your Plant Hardiness Zone

Knowing your hardiness zone will tell you which plants will—and will not—thrive in your garden. If you are in zone 13 and grow a plant that prefers a colder climate, for example, it will likely not be able to withstand the heat and may die. Knowing your zone will also tell you when your first and last frost dates are. "The first and last frost dates are important in deciding when it is safe to plant outdoors, as well as when to take tender plants indoors," says Teri Speight, master gardener and author of Black Flora: Profiles of Inspiring Black Flower Farmers and Florists.

The Plant Hardiness Zones by Region

The USDA also breaks down gardening zones by region across the United States. These regions include North Central, Northeast, Northwest, South Central, Southeast, and Southwest. To better understand every region, look to these descriptions, which include the states in each region, the zones that run through them, and their typical climate conditions.

North Central

The climate is generally cooler across this region of the United States.

Zones: 2 through 5
States: North Dakota, South Dakota, Minnesota, Wisconsin, Nebraska, Iowa, Illinois, Kansas, and Missouri

Northeast

Temperatures vary greatly across the Northeast and encompass a wide range of zones.

Zones: 1 through 7
States: Michigan, Indiana, Ohio, Kentucky, Virginia, West Virginia, Pennsylvania, New York, New Jersey, Maryland, Delaware, Connecticut, Massachusetts, New Hampshire, Maine, Vermont, and Rhode Island

Northwest

Conditions in the Northwest are typically wet in the winter and dry during the summer.

Zones: 3 to 9
States: Washington, Oregon, Montana, Idaho, Wyoming, and Northern California

South Central

This region is generally defined as the area from the southern Great Plains to the Gulf of Mexico, say the O'Neals.

Zones: 6 through 9
States: Parts of Texas, Oklahoma, Arkansas, Louisiana, Mississippi, and Alabama

Southeast

The last frost date in this region typically occurs in April, but note that southern Florida does not experience a frost at all, says Justin Hancock, a horticulturist at Costa Farms.

Zones: 7 to 10
States: Tennessee, North Carolina, South Carolina, Mississippi, Alabama, Georgia, and Florida

Southwest

With the extreme heat in the Southwest, it's helpful to understand the high temperatures that peak during the summer, in addition to the extreme lows in the winter. "The Sunset zone maps are more precise than the USDA's since they factor in not only winter minimum temperatures, but also summer highs, lengths of growing seasons, humidity, and rainfall patterns," says John Clements, the director of gardens at the San Diego Botanic Gardens.

Zones: 3 to 10
States: California, Nevada, Utah, Colorado, Arizona, and New Mexico.

Mixed border in an English cottage garden. — R A Kearton / Getty Images

Popular Plants to Grow in Your Region

There are a range of plants that will thrive in your region. Consider these expert recommendations.

North Central (Zones 2 through 5)

Consider these favorites from the O'Neals for planting in this region.

Groundcover	Creeping Thyme (Thymus serpyllum) is a low-maintenance groundcover that can grow in Zones 2 to 9. "It produces masses of small, fragrant flowers in spring with its evergreen foliage, also providing fragrance to the garden during the growing season," the O'Neals say. "Creeping thyme prefers well-draining soil and full sun."
Vine	Clematis is a versatile vine that can grow in varying conditions in this region. "Not only does it make a beautiful flower, its foliage is dainty and beautiful, as well," they say.
Perennial	Coneflowers (Echinacea) are native perennials that are adapted to this region. "They produce large flowers in a variety of colors that attract pollinators," they say. "They prefer a well-drained soil and full sun." These thrive best in zones 3 to 9 when they are either planted in spring or fall.
Shrub	Lilac (Syringa) is an heirloom shrub that grows best in zones 2 to 8. It produces fragrant flowers in the spring and prefers full sun and well-draining soil. It can be planted in spring or fall.
Tree	Red Maple (Acer rubrum) is a fast-growing tree that can grow well in a variety of soil types and light conditions. It can be planted in zones 3 to 9. It's also best planted in the spring or fall.

Northeast (Zones 1 through 7)

Speight recommends these for plants to grow in the Northeast.

Groundcover	Sweet Woodruff (Gallium odoratum) grows best in part shade. "It usually grows 10 to 12 inches high with a spread of 18 to 20 inches," Speight says. This plant loves damp borders and grows tiny white flowers and green foliage. These are ideal for Zones 3b to 7. Another perk? It's easy to grow, no additional fertilizer required.
Vine	Clematis can also be grown in the North East. "Great for zones 4 to 8, this vine loves a full to part sun environment," says Speight. "A little compost or aged manure in the spring will keep this plant well fed. Mulch, when placed at least 2 inches away from the vine, will keep the roots cool."
Perennial	Hellebore (Helleborus) is a dependable perennial, best grown in zones 3 to 8. It easily spreads, as it drops seeds from the nodding blooms. "One major reason I love this plant is the upkeep is minimal," she says. "When the previous season's foliage begins to look tattered, cut them back at the base. This allows the blooms to stand tall and the new leaves to emerge." This flower begins blooming in late January and continues through May.
Shrub	Great for zones 3 to 8, the Osier dogwood (Corns servicea) can grow throughout all seasons in full sun to part shade. "The beauty of this shrub is revealed when pruning out the old growth," says Speight. "After a spring pruning, the new growth emerges in shades of red or coral. This color shows off in the winter garden, especially when there is snow or against an evergreen backdrop."
Tree	Redbud (cercus canadensis) is an easy-to-care-for native tree that grows in zones 4 to 9. "From the prolific pink blooms along the branches in the spring, to the heart shaped leaves, what is not to love?" says Speight. "It can grow in full sun or partly shaded environments. Redbuds can grow in less than perfect soils such as clay to loamy, well-drained soils."

Northwest (Zones 3 through 9)

Try growing these expert-approved suggestions, including a few from Martha, in the Northwest.

Groundcover	The Black Scallop Bugleweed (Ajuga reptans 'Binblasca' Black Scallop) grows best in zones 3 to 9. Martha has even grown this in her garden at her Bedford farm and loves its glossy foliage and bright blue flowers.
Vine	Best grown between zones 4 to 8, a climbing hydrangea will thrive in the northwest region. These plants need a rich soil and can live in full sun, partial shade, and deep shade.
Perennial	Coneflowers (Echinacea) provide intrigue well into autumn. "Thriving in zones 3 to 9, these perennials add beauty to the garden when in bloom over the summer months," says Speight. "In the fall, I leave the seed heads so they can drop and provide new seedlings, unless they are eaten by the birds over the winter."
Shrub	Boxwood (Buxus sempervirens), one of Martha's favorite shrubs, grows in zones 5 to 9. These are both fragrant and deer-resistant, so you'll be able to admire the ornamental shrub's beauty without worrying about animals or pests feeding on them.
Tree	Evergreen trees enjoy the cool, moist conditions in the northwest region. Martha says that this tree maintains its green foliage throughout the cold-weather seasons.

South Central (Zones 6 through 10)

The O'Neals share their recommendations for plants to grow in this region.

Groundcover	Creeping phlox (Phlox subulata) is a low-maintenance groundcover plant that is well-suited to the south central region. It prefers well-draining soil and full sun, and it can be planted in zones 7 to 10. Plant in the spring or fall.
Vine	Carolina Jessamine (Gelsemium sempervirens) is a fast-growing vine that produces fragrant yellow flowers in the spring. It prefers well-draining soil and full sun and can be planted in zones 7 to 9. It is best planted in the spring or fall.
Perennial	Black-eyed Susan (Rudbeckia hirta) is a tough native perennial that produces masses of yellow flowers throughout the summer. It prefers well-draining soil and full sun and can be planted in Zones 3 to 9. It is best planted in the spring or fall.
Shrub	Crepe myrtle (Lagerstroemia indica) is an incredibly popular shrub or small tree that produces showy flowers in a variety of colors throughout the summer. It prefers well-draining soil and full sun and can be planted in zones 7 to 10. It is best planted in the spring.
Tree	Southern magnolia (Magnolia grandiflora) is a native broadleaf evergreen tree that is noted for its attractive dark green leaves and its large, extremely fragrant flowers. It prefers well-draining soil and full sun and can be planted in zones 7 to 10. It is best planted in the spring or fall.

Southeast (Zones 5 through 10)

If you want to grow plants in the Southeast, consider these ideas from Hancock.

Groundcover	Lilyturf (Liriope muscari) is a great groundcover. "This drought-tolerant evergreen grows in sun or shade, and variegated leaf selections add a lovely note to the landscape," Hancock says.
Vine	Jasmine (Jasminum), a powerfully fragrant vine with star-shaped flowers, thrives in this region.
Perennial	In terms of perennials, sage (salvia) is an ideal species since there are selections you can grow throughout the region from Kentucky to the Florida Keys. Salvia black and blue are two of Hancock's favorites, as they bloom all year long in this region.
Shrub	Rosemary (Rosmarinus officinalis) is a landscape plant that grows throughout the southeast. It is deer- and rabbit-resistant, drought tolerant, and fragrant.
Tree	"One of my favorite trees that you see in much of the region is Red Maple (Acer rubrum)" says Hancock. "It's native to the region and is a reliable source of bold autumn color."

Southwest (Zones 3 through 10)

Consider these expert-approved plants that thrive in the warm, dry conditions of the Southwest.

Groundcover	White clover (Trifolium repens) is a groundcover that can grow in this region, as it thrives in temperatures ranging from 50 to 85 degrees in the spring.
Vine	Crossvine (Bignonia capreolata L.) will thrive when planted in full sun and well-draining soil. Once it is watered deeply during the first growing season, the plant will develop a sustainable root system.
Perennial	Poppies (Papaver) grow best in zone 7 in areas with low moisture and full sun. They need frequent watering in the germination period, however, once they are set in their location, they need limited water.
Shrub	Leadworts (Plumbago) like full sun and light, well-draining soil, says the Monrovia team. The evergreen grows in zones 9 to 11 and needs deep watering in the first growing season.
Tree	The avocado tree (Persea americana) grows in hot, tropical conditions in zones 9 to 11. This tree needs four to six hours of sunlight, a well-draining soil, and deep watering. Once the roots are established in the first growing season, you can water it less and watch it thrive.