View photos of the edible and medicinal plant, Juglans californica (California walnut), profiled in Wild Edible Plants of California.

A passage from Wild Edible Plants of California:

California walnut’s original distribution (especially NorCal walnut) is limited and considered rare. Through a century–plus of cultivation and plantings, both species are now relatively abundant, though it is thought that most current specimens contain some DNA from Black (Juglans nigra) or English walnut (J. regia).

View photos of the edible and medicinal plant Juglans major (Canyon walnut), profiled in Sonoran Desert Food Plants and Medicinal Plants of the American Southwest.

A passage from Medicinal Plants of the American Southwest:

In small, sub–laxative doses, Canyon walnut is tonifying and soothing to the gastrointestinal tract. It is mainly useful in quieting gastritis, irritative diarrhea, and intestinal inflammation with associated ileocecal irritation. Use the tea or tincture when chronic intestinal inflammation is causing nutrient malabsorption, particularly of fats.

View photos of the edible and medicinal plant, Juglans microcarpa (Texas walnut), profiled in the Wild Edible Series: Oklahoma and Texas: Vol 1.

A passage from Wild Edible Plants of Texas (Volume 1):

They should first be collected whole, air–dried, and then
shelled. A light strike with a hammer is usually all that is needed to break through the outer shell to the nut meat within.