- white alder, mountain alder, Alnus rhombifolia - tree of western United States
--1 is a kind of alder, alder tree
--1 is a member of Alnus, genus Alnus - sweet pepperbush, pepper bush, summer sweet, white alder, Clethra alnifolia - shrub of eastern and southern coastal United States having beautiful racemes of spice-scented white flowers
--2 is a kind of shrub, bush