heath = heather (and is also the common name for the entire family including azaleas and rhododendrons). You can often find heather varieties at nurseries. The red whortleberry in my avatar is also a heath.

Remember the scene of the three witches from MacBeth "When shall we three meet again? In thunder lightning or in rain? Where the place? Upon the heath. There to meet with MacBeth!" That's all the Shakespeare I can quote, though my son can recite reams and reams (he's an actor). I played one of the three witches in school when I was eleven.