I was surprised to find that I had never featured the USDA Plant
Hardiness Zone Map after all of these years. The hardiness map refers
to temperature and moisture trends that limit plant distributions. The
map can be used to predict whether a particular plant will tolerate
conditions at various locations; it can also be used to predict
special measures that may be needed to protect them as well. This
hyperlinked version is provided by the National Arboretum of the US
and provides links to each state. (***1/2) -S