Lythrum salicaria
Heterostylous plants having three flower morphs are termed "tristylous". Each morph has two types of stamens. In one morph, the pistil is short, and the stamens are long and intermediate; in the second morph, the pistil is intermediate, and the stamens are short and long; in the third morph, the pistil is long, and the stamens are short and intermediate. "Oxalis pes-caprae", purple loosestrife ("Lythrum salicaria") and some other species of "Lythrum" are trimorphic.