elderberries.com

This page on Celtic Tree Lore by Sarah the Swampwitch describes Elder Lore as a tree of Venus associated with the element of air. It also lists some herbal uses for the various parts of the plant. (Note that this page lists elder bark as a diuretic and a way to promote labor, and the leaves as being able to be made into drinks, poultices and salves - while most medical sources recommend treating the bark and leaves as poisonous. I'm not saying nothing can be done with those, but I'd recommend thorough research before trying anything with those.) Also lists details on magical uses, rituals and associations with the month of Elder, including the rook, the color blood-red, and the gemstone dark green malachite.