The Dryades are the beautiful Nymphs of the trees, groves and woods and mountain forests. They were the maidens of the oaks and pines, poplar and ash, apple and laurel. For those known as Hamadryades, trees sprung up from the earth at their birth, trees to which their lives were closely tied. While the tree flourished, so did its resident nymph, but when it died she passed away with it.

There were several classes of Dryades associated with a particular types of tree:

The Meliai were the Nymphs of the ash-trees. They sprang up from Gaia the Earth when she was impregnated by the blood of the castrated Ouranos. The men of the Silver Age married these Nymphai (in the time before women were created) and from them all of mankind was descended.

The Oreiades were the Nymphs of the mountain conifers. The first of these were offspring of the five Daktyloi and the five Hekaterides. Subsequent generations were descended from these elder Oreiades and their brothers the Satyroi. 
(NB The old forests of ancient Greece were primarily found high in the mountains, since the majority of the lowland forest had been cleared for farming. It was therefore natural for the Greeks to think of the Dryades as mountain-dwelling).

The Hamadryades were the Nymphs of oak and poplar trees. These were usually associated with river-side trees and sacred groves.

The Maliades, Meliades or Epimelides were Nymphai of apple and other fruit trees. They were also protectors of sheep. The Greek word melas from which their name derives means both apple and sheep.

The Daphnaie were Nymphs of the laurel trees, one of a class of rarer tree-specific Nymphai. Others included the Nymphai Aigeiroi (black poplar), Ampeloi (grape vine), Balanis (ilex), Karyai (hazel-nut), Kraneiai (cherry-tree), Moreai (mulberry), Pteleai (elm), and Sykei (fig).