The Dryads are the Nature spirits, or nymphs, of forests and trees. These supernatural creatures were part of the large family of nymphs, well known in Greece and the surrounding area, but they are also said to inhabit the entire world.
There are several divisions of Dryads, each of which have their special areas of expertise and magick. The Dryads themselves are the nymphs of forests and trees. Their close relatives, the Napaeae, the Aulonaids, the Hylaecorae, and the Alsaeids lived in woods, glens, groves, and valleys, while the Oreads belonged to the mountains and grottoes. The Hamadryads protected and cherished specific individual trees. Close cousins to these Dryads were the Naiads of the brooks, the Crenae and the Pegae of springs, and the Limnads of stagnant waters.
Sometimes these nymphs lived within the waters, sometimes in grottoes nearby. They were said to give the gift of prophecy and oracles, heal the sick, watch over the flowers of the area, and protect the fields and flocks. The relationship and powers of all the nymphs were so similar that often their duties and areas of influence overlapped. Dryads of the forests and trees sometimes watched over nearby pools and springs. Nymphs of the waters protected the surrounding woodlands.
Dryads were known in all the Celtic countries. The Celts believed them to be spirits who dwelt in trees, oaks in particular. The Druids contacted them for inspiration. Oak galls were known as Serpent Eggs by the Druids and were used in many of their charms.
The ancient people who knew about the Dryads were careful not to antagonize them. Grottoes, springs, groves, and all woodlands were treated with respect, for one never knew if the presiding nymph would be offended. Nymphs were companions of Faunus and Pan, both of which were capable of instilling panic and unnatural dread in any offender. To see them was considered unlucky, but this may be because as vigilant guardian spirits they most frequently made themselves visible when displeased and intent on inflicting disciplinary action.
If trees must be cut, Dryads should be given due notice and propitiatory offerings. If trees have already been cut, erect an altar by the tree with lavish offerings and hope for the best. Appropriate offerings include: milk, water, wine, oil, and honey.
From: Moon Magick and other sources