Finding Your Geographic Zone
Plants Grow Best in Their Own Hardiness Zones
Use the USDA's Plant Hardiness Zone Map to ensure the plants you choose for your landscape will survive even the most extreme weather conditions.
What’s Your Plant Hardiness Zone?
That's an important question to answer when determining which plants will work best in your landscape. Learning your geographic zone is just one of those details.
Once you determine a basic design for the landscape or garden you’d like to create, it’s time to get down to the business of choosing your plants. It’s important to focus on plants that will be compatible with your environment.
The U.S. Department of Agriculture bases its plant hardiness zone map, which is used by the National Arboretum, on the lowest measured temperatures across the United States, Canada and Mexico.
Plant hardiness zones are numbered from 1 to 11, from coldest to warmest. The department’s most recent version of the zone map, revised in 1990, also divides zones 2 through 10 into “subdivisions” that represent 5 degree Fahrenheit (2.8 Celsius) differences within the 10 degree Fahrenheit (5.6 Celsius) zone. The light color of each zone represents the colder section; the dark color, the warmer section.
In addition to the sub-zones, the map takes into consideration such details as elevation and urban heat islands, which is why the zone lines don’t run in smooth horizontal lines.
What does this mean to the average gardener? Plants that will work in, say, Zone 11 (a basically frost-free zone, largely found in Hawaii and parts of Mexico) with lowest temperatures above 40 degrees will not work in Zone 1, Alaska and the Northwest Territories. That may seem obvious, but get a little closer between zones and things can get tricky. Many states have several zones, so it’s important to know how your specific geographic location, as well as your terrain, will affect your zone.
There is also a plant hardiness zone map for Europe.
A nursery may carry other plants compatible with other zones, too, and here’s why: A yard can have varying temperatures and conditions. According to Better Homes and Gardens Step-by-Step Garden Basics, your property has microclimates – small pockets where prevailing temperatures vary. For example, areas near your house can be as much as one zone warmer than other parts of your yard. Exposed slopes will experience more extreme temperatures.
Choosing your plants
When you begin looking through garden books and seed catalogs, you’ll need to base your choices in part on the zone you’re in. Otherwise, what you order isn’t likely to survive.
When you head to your local nursery or garden center, you’ll find the majority of plants that should be compatible with the zone you live in. Reputable garden centers have knowledgeable staff that can help you determine what will work best in your yard. Plants’ zones are marked on their tags, along with required sunlight, water and feeding needs and planting instructions.
When you make your plant choices, keep these things in mind:
- What zone is closest to my geographic location?
- Am I living in a subdivided zone?
- What features in my yard might cause some areas to be a different zone than others?
Answering these questions on the front end can help make your gardening easier and eliminate the waste that comes from poor plant choices.
