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CommentsThe common name, 'Scarlet Toothcup,' refers to the appearance of the fruits when they begin to ripen during the fall. Another common name for this species is 'Purple Ammannia,' which refers to the color of the flowers. Scarlet Toothcup is a wetland species that is not very showy and often overlooked, although it is useful as a source of food for waterfowl. The only other species in this genus that occurs in Illinois, Ammannia robusta (Robust Toothcup), was formerly regarded as a subspecies of Scarlet Toothcup, or Ammannia coccinea robusta. However, genetic analysis has revealed that it is a distinct species. Robust Toothcup occurs primarily in NE Illinois and has an appearance that is similar to Scarlet Toothcup. The petals of its flowers are light pink to pink and there are only 1-3 flowers (or seed capsules) per leaf axil, whereas Scarlet Toothcup has flower petals that range from pink to purple and there are often 3-5 flowers (or seed capsules) per axil among the lower leaves (and sometimes even more). Another wetland species in the Loosestrife family with a similar appearance is Rotala ramosior (Wheelwort). Unlike the preceding Toothcup species, Wheelwort has only a single flower or seed capsule per leaf axil, and the petals of its flowers are white. Whereas the Toothcup species have leaves that clasp their stems, the leaves of Wheelwort are sessile.