Califonia black walnut (Juglans californica) is a deciduous tree growing up to 80 ft. Its bark is gray to dark brown. When flowering the male flowers hang in catkins while single female flowers sit in the angle between leaves and stems. Green fruits have a smooth fleshy husk. Besides food and habitat for animals, the fruit is edible. It had uses as dyes as well. There are other species of walnut in the Nature Center, since in the early 1900's this site was the biggest walnut growing area in the U.S. The planted trees were English walnuts, better suited for exploitation, but now we find some hybrid specimens as well.