Plants that survive freezing winters are called hardy, while those that succumb to cold weather are called tender. The plants on this site are rated according to the coldest temperatures they can survive. Summer heat and humidity and lack of winter chilling in warmer climates may limit the ability of some plants to thrive. Because of this, and the fact that within each zone are microclimates that can be colder or warmer, we suggest that you use the zones as a guide, but feel free to experiment with plants rated marginally hardy in your area.

Zones in North America are based on average minimum temperatures, with zone 11 rated warmest, and zone 1 coldest. Each zone can grow plants from lower numbered zones. For example, if you live in zone 4 you can include plants from zones 3, 2, and 1 in your garden.