Hmm. Welcome to the boards. I have never heard of those yuccas, but they sound interesting. If they are rated for zones 9-11, it is highly unlikely that they will survive anything lower than a 8A climate zone. Sounds like a yucca native to south Florida or somewhere in Mexico, or southwest coast?

I am sure someone here can provide more info however.

Good luck!

shinythumb,

Unfortunately, Y. elephantipes is not hardy in zone 7. It is a 9b plant (perhaps warm and dry 9a). But take heart, there are other trunking yuccas that do survive in zone 7. Check out Yucca gloriosa, Yucca recurvifolia, Yucca elata, Yucca thompsoniana, and Yucca rostrata to name a few. But Y. elephantipes is a houseplant in our zone. You could probably leave it in the ground this summer, then dig up in the Fall to winter over indoors.

Also Yucca filamentosa