Erect plant, to 3 feet tall. Leaves opposite, stalkless, untoothed or with small teeth, oval, pointed. Flowers in long clusters, with four blue to violet petals. Lower petal is smaller than the others.

A native wetland species. In Wildwood found in the wetland at the entrance.

All speedwells, of which there are several in the Park, have flowers with one undersized petal. Of these, most are smaller and found in drier places than water speedwell. Marsh speedwell (V. scutellata) is similar in size and habitat, but has very narrow leaves, usually untoothed, and has not yet been found in the Park..