Alternate name: Water-willow
Family: Acanthaceae, Acanthus view all from this family
Description Herbaceous, aquatic flowering plant. Grows in dense clusters partially submerged in still or flowing water, reaching up to 40 cm (1 ft. 4 in.) tall from a creeping rhizome.
Flowers: bicolored, born in opposite arrangement on spikes 3 cm (1 in.) long coming off a peduncle 10 cm (4 in.) long. Color ranges from white to pale lavender with the upper corolla lip pale violet or white, arching over the lower lip mottled in dark purple. The lateral lobes are unadorned or slightly blushed. The anthers are purplish-red rather than the usual yellow.
Leaves: to 10 cm (4 in.), opposite, sessile, linear or lanceolate, and slightly crenulated.
Habitat Shorelines of still or slow waters in lakes and rivers, rocky riffles and shoals in faster flowing rivers.
Range Florida north to New York, Quebec and Ontario, west to Texas and then North to Michigan and Wisconsin.
Discussion Often forms large colonies on or near shorelines with rhizomes and roots providing important spawning sites for many fish species and habitat for invertebrates. Hardiest species in the genus Justicia, the other members of which are largely tropical and subtropical.