How to Use Hardiness Zones for Plants to Decide What to Grow

Let's say you've just heard about a gorgeous perennial or maybe a spectacular shrub that you want to add to your garden. But will it survive in your region? This dilemma is why the USDA Plant Hardiness Zone Map was created. A glance at it, and you can figure out what your hardiness zone is. Terrific, now what? Most hardy plants have a zone rating to indicate where they will survive the winters from year to year. Maybe the plant you have your eye on is hardy in Zones 5-9, and you live in Zone 4. That could be iffy, but you could try it if you don't mind a little risk for the thrill of growing something that normally wouldn't survive in your region. Or, you could play it safe and find another plant that can withstand your area's coldest temperatures. Either way, here's how you can use USDA Plant Hardiness Zones to guide your decision.

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.