 The acorn has a cap up to 2 centimeters (0.8 inch) wide and a nut measuring 2 or 3 centimeters (0.8–1.2 inches) long.This oak often produces a stable hybrid with "Quercus lobata", that has been named "Quercus" × "macdonaldii".This oak species is threatened by a pathogenic honey fungus ("Armillaria" sp.