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Plant Highlight: Yucca thompsoniana

June 2011

The genus Yucca is very well-represented in the U.S., with species occurring from the east coast to the west coast, and from the northern Great Plains down to the Mexican border.  Some kinds span the southern border, growing in the U.S. and in Mexico as well.  One such species is Yucca thompsoniana, found in west Texas and in adjacent areas of northeast Mexico.  It is closely related to Yucca rostrata, which is more commonly seen in cultivation, but plants of Yucca thompsoniana branch more and tend not to grow as tall.  Also, the foliage of Yucca thompsoniana are greener, rather than glaucous-bluish as with Y. rostrata.

The leaves of Yucca thompsoniana are about 7 to 12 inches long (18 – 30 cm) and about ⅔ of an inch wide (1 cm).  They are thin and pliable rather than thick and rigid, with a narrow yellow or brownish margin edged with many minute teeth.  Though plants develop a trunk, they remain on the short side, seeming to put their energy into branching rather than height.  Our plant at the Ruth Bancroft Garden has grown into a 40-headed impressive specimen, but it is only about 10 feet tall.

Yucca thompsoniana comes into flower in late May or June, with slender flower stalks rising above the leaves and bearing branched panicles of white flowers.  The flower cluster is widest at the middle, tapering at the top and bottom.  The flowers themselves are snow-white and downward-facing, with pointed tepals which are normally about 1½ to 2½ inches long (about 40 to 65 mm).