The U.S. Department of Agriculture produces the Plant Hardiness Zone Map, which is available on its website and also from organizations such as the Arbor Day Foundation and the National Gardening Foundation. Visitors can search by zip code or view detailed maps of their areas to determine their zones.Continue Reading
The Plant Hardiness Zone Map splits up North America into 11 separate growing zones, which are ranked in terms of average temperatures. Each zone is generally 10 degrees Fahrenheit warmer or colder than the zones next to it. Although there are only 11 general zones, all zones but 1 and 11 are actually split up into separate A and B zones in many versions of the map.
This map is useful because it gives a fairly good estimation of the plants that can survive in a specific area based on its climate. Most plant and seed catalogs list the zones where each plant can grow in their descriptions. This means that by determining the zone he lives in, a person can learn which plants he should or shouldn't plant.
There are a few criticisms about the accuracy of the map that are mainly related to how it divides the western half of the continent. The map is quite accurate for most of the eastern half of the country, but it fails to take into account the varied precipitation and elevation levels in the west, making it less reliable for points west of the 100th meridian.Learn more about Outdoor Plants & Flowers