narrow leaved yucca bloom

I think this is

Yucca angustissimai Engelmann ex Trelease ssp.angustissima

It was the first yucca specimen in my handy dandy guide -
most unusual, it usually takes me hours to identify anything!
So perhaps it's actually something entirely different ...

A good 30' high, it is at the end of its life cycle and the whole plant will die off soon.
The trees beneath are palo verdes, also in bloom for a few heavenly weeks when we seem to be basked in floral displays.