Yucca Tromping Around

I fell in love with this unusual yucca when I first saw it in the amazing Trompenburg Arboretum in the Netherlands. Unfortunately, their plant records were no help in figuring out its origin, but after returning home with a cutting (legally) and growing it since 2004, we're confident that it's either a giant leaf form of our naturally occurring Southeastern US hybrid, Yucca x gloriosa (filamentosa x aloifolia) or more likely a hybrid with that and the native Yucca flaccida. Yucca 'Tromping Around' forms a 5' tall x 7' wide, multi-headed specimen, clothed with 32" x 3" wide glaucous blue leaves. The clumps are topped, starting for us in late September with red-tinged stalks that tower 3' above the foliage, each holding a bough of creamy white bell-shaped flowers.