The pith is the soft inner core of the twig. The trees easily identified by its pith are black walnut and butternut (both with chambered pith) and hickory (tan, 5-sided pith). One bit of caution ...

There are five native walnut species in North America: black walnut, butternut, Arizona walnut and ... confirm the tree's identification when a twig is cut open. The fruit of a walnut is a rounded ...

Even though the walnut twig beetle is likely native to Arizona ... The five species of native black walnut trees and butternut trees are also important ecological components of riparian corridors ...