The classification of asparagaceae has changed over the years, and is now considered to include seven subfamilies (Agavoideae, Aphyllanthoideae, Asparagoideae, Brodiaeoideae, Lomandroideae, Nolinoideae, Scilloideae) which, under different names, were originally classed as separate families. Most species have lily-like flowers, single or in dense clusters, generally borne on stems which either have no leaves, or rise well above the leaves. Plants differ greatly in appearance, ranging from tiny herbs to the huge Joshua tree, this in the agavoideae subfamily. The US has around 53 genera and 220 species.