The ogham  

Willow

The Ogham alphabet is the earliest known form of the Irish writing. It dates from the first century BC and was widely used by the Celts for centuries. Ancient Ogham writing can still be found on many standing stones throughout Ireland and the British Isles. Ogham writing is read from bottom to top.

Every wand I craft has the ogham symbol for that specific wood burned somewhere near the bottom of the wand.

Elder  

    Blackthorn