Dear Carol;
I am going to be ordering some plant collections, something I have never done. In shopping the catalogs it occurred to me that I may not always understand the plant hardiness chart. It a notation says the plant is hardy to zone 9, does it mean to plant it in zones 9 through 11, or does it mean it will grow from in zones 1 to 9. Most of this is common sense and plant knowledge, but I confess that some of the new varieties have me wondering.
Jenny
Vero Beach

Hello Jenny,
The USDA Plant Hardiness Zone map is a guide, not a be all to end all. The official version on the map and all of the supporting information is available on the web at the National Arboretum's site at http://www.usna.usda.gov/Hardzone/index.html

The Zones are based on the "average minimum temperature" as recorded for each of the years 1974 to 1986 in the United States and Canada and 1971 to 1984 in Mexico, so this makes this map a good place to start. When a plant has a USDA Hardiness Zone on it's tag, that is just a guideline suggesting that the plant will grow in that Zone. Usually a tag will say from Zone XX to XX, I would not assume growth in a zone not listed.

However, this map does have some shortcomings, it does not consider heat, precipitation or lack thereof like our particular wet and rainy seasons. It does not consider individual plants response to cold or hot weather. Your local nurseries and Extension Service will have great list of plants for this area.

Check out the BLOG entry "Some Like it Hot" for another look at Hardiness Zone info.

Happy Gardening,
Carol