These large plants of the agave family are closely related to the Joshua trees of the Mohave desert. Also called Spanish dagger and Spanish bayonet, the several varieties of yucca have stalks of white, waxy bell-shaped flowers that later form large black seed pods. American Indians used the fibrous leaves for weaving baskets, sandals and mats, and they made soap from the plants by soaking the dried roots in water to produce a lather.
The photo below shows banana yuccas, bearing their distinctive chunky seed pods, among ocotillo plants, near the Dragoon mountains along Middlemarch Road.
Seeds of the yucca plant, approximately actual size
Epple, Anne Orth. A Field Guide to the Plants of Arizona . Helena, MT: Falcon Publishing, Inc., 1995.