Heartwood
Heartwood (Also known as Cedar) is a slightly magical tree found all over Azeroth. Heartwood is naturally resistant to disease, rot and plague and its known for its fragrance.
Because of it's resistance to rot, it's considered a sacred tree to many cultures and utilized in multiple healing and purification rituals. It's made into religious tools and burnt as incense. The tree is believed to be empathetic.
For darker rituals, it is said burning heartwood increases the effectiveness of a ritual to summon a sayaad.
A great Heartwood tree is found in the ruins of Ordil'Aran in Ashenvale. It is said to grow over the graves of two lovers that died fighting during the War of the Ancients, and often serves as a place of pilgrimage for newly weds.
Crystalline Heartwood is a variety that grows specifically in Crystalsong Forest. Intense arcane corruption has made the wood's properties even more intense, to the point the trees are likely incapable of getting sick.