When I started studying horticulture, I learned about the United States National Arboretum’s Plant Hardiness Zones. The USDA has every inch of the country classified into a zone, with a number that gives you a good guide to what plants will survive in your area. If you go to http://www.usna.usda.gov/Hardzone/ushzmap.html, you’ll find a map that will tell you what your zone is. (The colors aren’t great on the maps, so it can be hard to figure out. Another strategy is to do an Internet search for USDA zone with your state name and you’ll get a map that’s much easier to read.)
Plant hardiness zones are a guide to the severity of winter temperatures a plant can survive. The American Horticulture Society also has a heat zone system that tells you how much sweltering plants can endure. You’ll find it at: http://www.ahs.org/publications/heat_zone_map.htm
Most nurseries and plant books use the USDA zone system, but more and more plants are being classified by heat zones as well. It’s the first piece of information to ask about a plant, and you should make sure that with every purchase you check out the plant’s hardiness zone rating. It just doesn’t make sense to pay for a perennial that won’t survive your winter.
Still, the USDA map isn’t fool-proof. It doesn’t take account of snow cover, which can moderate temperatures, and for the western part of the country, it’s much less useful because it doesn’t include the effects of wind or elevation. Your state, however, probably has lots of good resources. A Cranky search using your state and the word “arboretum” or “plant information” will take you to sites where you’ll be able to learn what plants are native to your region, what grows well there, what some typical problems are, and how to understand your climate as it affects plants.
by Rinda West
