Elder:
Elder is said to offer protection to the faeries from negative spirits.

Hawthorn:
Hawthorn, also known as Witches' Tree, is one part of the sacred triad of trees that are said to be sacred to the Faery. Oak, Ash, and Thorn, when growing naturally together, create a place where it is easy to see the Fey. Hawthorns were once believed to be the transformed bodies of Witches, who had shape shifted into tree form. It is more likely that the spirit seen in the Hawthorn was that of a dryad or tree faery.

Oak:
Legend tells us that "Faery folks are in the oaks". Oak trees are believed to provide safe havens and homes for many varieties of faery.