Dryads

In Greek mythology, the dryads are female spirits of nature (nymphs), who preside over the groves and forests. Each one is born with a certain tree over which she watches. A dryad either lives in a tree, in which case she is called a hamadryad, or close to it. The lives of the dryads are connected with that of the trees; should the tree perish, then she dies with it. If this is caused by a mortal, the gods will punish him for that deed. The dryads themselves will also punish any thoughtless mortal who would somehow injure the trees.

Originaly dryads were spefically, nymbps of oak trees, as the name itself comes froms the Greek word drys which means oak, but later the came to represent all tree nymphs, though formally there were different names, for the nymps of different trees.

Meliai were the nymphs of ash trees. The ash-tree sisters tended the infant Zeus in Rhea's Cretan cave. Rhea gave birth to the Meliai after being made fertile by the blood of castrated Ouranos. They were also sometimes associated with fruit trees

Daphnaie were they nymphs of laurel trees who spent most of their time sleeping, only coming out when no one was around

Dryads." Encyclopedia Mythica from Encyclopedia Mythica Online.
http://www.pantheon.org/articles/d/dryads.html

http://en.wikipedia.org/wiki/Dryad