Yucca Rostrata x Yucca Rigida Hybrid. 
The Yucca Rostrata x Yucca Rigida is probably one of the most beautiful hybrids. Relatively slow growing, this sculptural yucca is perfect for providing a dramatic accent to your garden design.
One of the most cold tolerant, it is hardy to winter wet as well as severe cold when established, down to temperatures of -15 degrees. Pale blue/silvery leaves, slightly wider than that of the rostrata, are arranged in an attractive symmetrical rosette. This is a remarkably beautiful Yucca.