From The Collaborative International Dictionary of English v.0.48 :
Ledum \Ledum\ prop. n. A genus of evergreen shrubs of the north temperate regions. Syn: genus Ledum. [WordNet 1.5]From WordNet (r) 3.0 (2006) :
Ledum n 1: evergreen shrubs of north temperate regions [syn: Ledum, genus Ledum]