Yucca spp.

Chloride, Arizona. We always called this ground-hugging variety, with the slightly bluish cast, "Spanish dagger" when I was a kid, but evidently that's so broadly applied as to be useless. (Wikipedia claims that "Spanish dagger" is applied only to a variety in the southeastern US, but other sources indicate that's wrong. Misinformation in Wikipedia--perish the thought! ;) Anyway, this is probably Y. harrimaniae, based on its location. It's probably not blue yucca (Y. rigida), despite the color, because it has no stem. Yuccas belong to the same family as agave, but bloom more than once.