Black Oaks can grow to heights of 50-110 feet when mature, but are typically 30-80 feet. In close stands, they develop narrow thin crowns while trees grown in the open develop broad crowns with multiple stems that fork repeatedly. The grey bark is thin and smooth in young trees, becoming thick, ridged, and plate-like with age. The dark leaves are deeply lobed and can grow 4-8 inches long. Male flowers are greenish red, 1.5-3 inches long, and have bright red anthers and pale green filaments. Female flowers have dark red stigmas. Seeds are acorns with a light brown thin scaled cap that mature the second summer after pollination. Acorns may form singly or in clusters of up six, varying widely in size.

California black oaks are the most abundant oak on the West Coast. They are intolerant of shade and their population is declining due to fire suppression. They can regenerate through acorn germination and by sprouts that emerge after the parent tree is cut or burned. Acorns constitute an average of 50% of the fall and winter diets of western gray squirrel and black-tailed deer. Fawn survival rates increase or decrease with the size of the acorn crop.