Perennial Herb or Tree: Evergreen. Deer resistant. A slow-growing tree-like yucca with upright stems & beautiful gray-blue narrow foliage. Although it can branch, it is most often seen with a single trunk, that can grow to 12-15' tall. The 2' long, stiff, slightly waxy, pale bluish-green leaves with yellow margins, form a dense rosette on top of the stems. Water: dry.