Diamond Willow does not refer to a particular species of willow, but is a description of an abnormal growth form of certain fungus-infected willow trees. The tree grows diamond-shaped cankers in response to the fungus. These deformations create interesting shapes and patterns—especially once the bark has been removed—making diamond willow a prized material for use in walking sticks and other carved objects.

There are six or seven currently known species of willow (out of hundreds of species) that produce the diamond growth formations, the most common being Bebb’s Willow (Salix bebbiana).