This USDA plant hardiness zone map is based on USDA Miscellaneous Publication
814, "Plant Hardiness
Zone Map," which was revised in 1965 and more recently in 1990.
Zones
represent average annual minimum temperatures, in 10°F increments.
Ornamentals
are species (not varieties) that are commonly
planted.
Clicking on a state generates a listing of native and naturalized species
for that state.
For our purposes, zonal subdivisions in the original map have
been combined.
For the original map, along with additional information, please visit
the National Arboretum
Original map boundaries were based on interpretation of available
vegetation/floristic maps such as in Goode's world atlas, Gleason
and Cronquist's
Plant Geography, and Bailey's
ecoregions.
THIS IS NOT AN EXACT SCIENCE! For example, small populations of Boreal
Forest species can be found at High Elevations in the Appalachians.
They are not represented on this "painted" map. The intent is to provide
GENERAL information, and (hopefully) aid end users with their tree
identification
needs.