Frost Zone Map and Tender Perennials

This is the best temperature zone map I have found so far. Note that if container gardening you must subtract 2 zones from the zone you are currently in. For example, here in Memphis we are zone 7. So over the winter, any plants you have in containers will actually be like they are in zone 5 because the roots are not  protected. In soil, the roots are protected and might stay 20 degrees warmer than if they were in containers. Some plants like the brugmansia (angel trumpet) is hardy to zone 7, but will often die if we have a little colder than normal winter, even if planted straight in the ground and covered with a bucket, mulch, etc. It is best to always have a few cuttings inside over the winter so you dont permanently lose a valuable plant. If you have a good enough quality greenhouse with heat then you need not worry about this. However this can be expensive. Also note that some plants like coleus, impatients, and begonias, although classified as annuals, can actually be kept alive by bringing them inside for the winter. Just remember plants still need light so either place your plants that you bring inside in a room with a window, or hook up a couple flourescent fixtures. Also, only water them when they are almost completely dry.