What Is the USDA Plant Hardiness Zone Map?
You’ve probably run across the USDA Plant Hardiness Zone Map or references to it in garden magazines and books, as well as on seed packets or in plant catalogs. This map divides the United States into 11 separate zones (each of which are then divided into a and b). Each zone is 10°F warmer (or colder) in an average winter than the adjacent zone. The lower the zone number, the colder the region. Although factors other than temperature affect a plant’s ability to survive in a particular climate, the USDA map is a good starting point when you’re trying to decide what to grow, especially if you live in the eastern half of the country. That’s because this area is comparatively flat, so mapping is mostly a matter of drawing lines approximately parallel to the Gulf Coast every 120 miles or so as you move north. The lines tilt northeast as they approach the Eastern Seaboard. They also demarcate the special climates formed by the Great Lakes and by the Appalachian mountain ranges. But in other areas of the country, elevation and precipitation can have more of an effect on plant survival than just temperature.
What You Can Grow in Your Hardiness Zone
For annual flowers such as petunias and vegetables such as zucchini, you don’t need to pay attention to hardiness zones because these plants usually complete their life cycle (seed sprouting to seed producing) in a single year. You might see these plants given a zone rating of 0 to indicate they aren’t hardy anywhere. But when you’re dealing with perennials, vines, shrubs, and trees that typically live for many years, you’ll want to find out the coldest temperatures a species is expected to survive and compare that to the zone you’re in. When considering the hardiness zones a particular plant is rated for, think of that information as a guideline, not a guarantee that it will survive in your climate. The list below provides examples of plants that can take the cold in each USDA Hardiness Zone. Only the coldest zone for each listed plant is considered; some of the plants won’t thrive in substantially warmer areas. Always check with the source of your plants for information on whether they are well-suited to your area. When to Plant: Mid-June Common Plants:
Netleaf willow (Salix reticulata) Dwarf birch (Betula glandulosa) Crowberry (Empetrum nigrum) Quaking aspen (Populus fremuloides) Pennsylvania cinquefoil (Potentilla pensylvanica) Lapland rhododendron (Rhododendron lapponicum)
When to Plant: Mid-June Common Plants:
Paper birch (Betula papyrifera) Bunchberry dogwood (Cornus canadensis) Silverberry (Elaeagnus commutata) Eastern larch (Larix laricina) Bush cinquefoil (Potentilla fruticosa) American cranberry bush (Viburnum trilobum)
When to Plant: Mid-May Common Plants:
Foxglove (Digitalis selections) Wood fern (Dryopteris selections) Smooth hydrangea (Hydrangea arborescens) Common juniper (Junipercus communis) Siberian crabapple (Malus baccata) Goldenrod (Solidago selections) American arborvitae (Thuja occidentalis)
When to Plant: Mid-May Common Plants:
Sugar maple (Acer saccharum) Panicle hydrangea (Hydrangea paniculata) Chinese juniper (Juniperus chinensis) Vanhouffe spirea (Spiraea x vanhouttei) Crabapple tree (Malus selections)
When to Plant: Mid-April Common Plants:
Flowering dogwood (Cornus florida) Delphinium (Delphinium selections) Slender deutzia (Deutzia gracilis) Boston ivy (Parthenocissus tricuspidata) Sycamore tree (Platanus occidentalis) Japanese yew (Taxus cuspidata)
When to Plant: Mid-April Common Plants:
Japanese maple (Acer palmatum) Common boxwood (Buxus sempervirens) Coralbells (Heuchera) American holly (Ilex opaca) Weeping willow (Salix babylonica)
When to Plant: Mid-April Common Plants:
Bigleaf maple (Acer macrophyllum) Atlas cedar (Cedrus atlantica) Bleeding heart (Dicentra) English holly (Ilex aquifolium) Magnolia tree (Magnolia selections) Texas rock rose (Pavonia lasiopetala) Kurume azalea (Rhododendron Kurume hybrids) English yew (Taxus baccata)
When to Plant: Mid-March Common Plants:
Strawberry tree (Arbutus unedo) Mexican orange (Choisya temata) Hibiscus (Hibiscus selections) New Zealand daisy-bush (Olearia haastii) Japanese pittosporum (Pittosporum tobira) Cherry-laurel (Prunus laurocerasus) Texas mountain laurel (Sophora secundiflora) Laurustinus (Viburnum tinus) Yucca (Yucca selections)
When to Plant: Mid-February Common Plants:
Asparagus fern (Asparagus setaceous) Dahlia (Dahlia selections) Tasmanian blue gum (Eucalyptus globulus) Fuchsia (Fuchsia selections) Silk-oak (Grevillea robusta) Sweetshade tree (Hymenosporum flavum) California pepper tree (Schinus molle) Australian bush cherry (Syzygium paniculatum)
When to Plant: Mid-January Common Plants:
Bougainvillea (Bougainvillea spectabilis) Golden shower (Cassia fistula) Ensete (Ensete ventricosum) Lemon eucalyptus (Eucalyptus citriodora) Rubber plant (Ficus elastica) Violet churcu (Iochroma cyaneum) Royal palm (Roystonea regia) Palmetto palm tree (Sabal spp.)
When to Plant: Any time Common Plants:
Lime (Citrus aurantiifolia) Sago palm (Cycas revoluta) Grevillea (Grevillea)
