Ah yes, a century plant in bloom, a true Tucson native plant. This is a short and round yucca that blooms a tall stalk like this when it is mature. (You are actually seeing two plants here). However it is not a hundred years old when this happens (more like forty I think), as was erroneously believed - giving the rise to its common name of century plant.
Interesting information! I've seen something like that (might be of the same family) on the island of Curacao, where Venezuelan Troupials (Icterus icterus) and Bananaquits (Coereba flaveola) came to 'have a drink' of the plant's nectar. Beautiful sight!
