This Yucca species was first collected from the wild in the 1980s. It was thought to be a variant of Y. rostrata, but has recently been identified as a distinct species. The foliage is narrower and more succulent than that of Y. rostrata. Seed production has been rare, so it has been introduced into commerce via tissue culture.
In my garden it has grow considerably albeit slowly, but still measures at a dainty 18". Eventually it should form a short trunk. The plant's overall symmetry and narrow foliage is quite lovely, and maintenance required has been zero.
Yucca linearfolia with Dyckia 'Dark Star':
Update: here it is a year and a half later, December 2012: