Nearly all Heucheras (Coral Bells or Alum Root) are cold hardy in zones 4-9.

USDA Plant Hardiness Zone Map

The Heuchera genus is native to North America and therefore is a good fit for many gardens.

Coral Bell Winter Considerations:

Coral Bells are described as an evergreen perennial, Heucheras will provide great winter interest in warmer climates with mild winters as they retain their foliage.  In colder climates, with hard frost or snow, Heucheras, and in particular first year Coral Bells should be given winter protection by adding an insulating layer, such as a pile of leaves, straw, or even snow.

Coral Bell Summer Considerations:

In warm climates, with very hot or humid conditions, look for species native to the southeast.  Hybrids with lineage from H. villosa or H. americana often perform well.  These species are found in mountain habitats and may benefit from being in well-drained containers as opposed to planted directly in the ground.  Additionally, heuchera benefit from cooler nighttime temperatures.