For years you've been buying seed packets with the USDA Plant Hardiness Zone Map on the back, right? If asked, you could state your plant zone number as quickly as your street number -- and were darn proud of it, too. But as this article on plant zones explains, the USDA Plant Hardiness Zone Map is not the sole zone-meister. Other planting guides include:

• the AHS Heat-Zone Map
• the Canadian Plant Hardiness Zone Map
• the Sunset Climate Zone Map

Go ahead and discover how these maps differ, but just don't go crazy trying to reconcile your landscape design to all these additional zones. Fretting about this too much could land you in the "Twilight Zone."