Yucca Rigida. 
The Yucca Rigida is a beautiful, tall, relatively slow growing sculptural yucca perfect for providing a dramatic accent to your garden design.
One of the most cold tolerant, it is hardy to drought as well as severe cold when established, down to temperatures of -12 degrees or lower when drainage is good. It’s thin, pale blue/silvery leaves are usually wider and less flexible than the Yucca Rostrata, which it sometimes can be confused with. Arranged in an attractive symmetrical rosette it’s leaves are lined with a thin yellow margin and very tiny teeth. This is a remarkably beautiful Yucca.
Generally a single trunked species, but occasionally it can form multiple trunks!