Agave spp., possibly A. mckelveyana due to its altitude, here outside Sedona, Arizona. There are quite a number of agave species, with great internal variation, and it seems the taxonomy is something of a mess. A.k.a. "century plant," from the folk belief that the flowering stalk only grows after a century. In fact the plant usually flowers in one to three decades--still a remarkable delay! The original plant then dies, but it usually has propagated by rhizomes (runners), so that the living specimen above is probably a clone of the original. Off the Brin Mesa trail, just outside Sedona. Map location is approximate.