The term dioecious is typically used only in plants and plant species. Dioecious refers to a plant population having separate male and female plants. No individual plant can produce both microspores and megaspores; individuals of the species are either androecious (male, producing microspores) or gynoecious (female, producing megaspores). Dioecious species cannot self-fertilize.
Individual plants are either male or female.[4] From Greek for "two households". [Individual plants are not called dioecious; they are either gynoecious (female plants) or androecious (male plants).] In most dioecious species the female plant is of homogametic sex XX and the male plant is of heterogametic sex XY. Exceptions where the male plants are of homogametic sex are Potentilla fruticosa and species of Cotula.[citation needed] Some plant genera are exclusively dioecious, such as willows and poplars.