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Waterwillow - Justicia americana
Family: Acanthaceae

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Description

Plants are rhizomatous and colonial. Stems are more or less 4-angled, coarse, often bent below and rooting at the nodes, ascending above to about 1 m tall. Leaves are opposite, lanceolate, linear or linear elliptic, sessile, triangular at the base, acute apically to 20 cm long and up to 2 cm wide. The flowers are in leaf axils, with bracts, in dense, short-oblong spikes that are on stalks. Flowers are violet to nearly white with brownish purple markings on the lower lip. The fruit is a 4-seeded capsule.

Interesting facts

This species grows in shallow water, margins and beds of streams, marshy shores of ponds, lakes, and ditches. Waterwillow grows best in 0.15 to 0.5 m of water and on course substrates of sand and fine gravel (Penfound 1940). However, it will grow on finer textured sediments and at depths up to about 1.3 m. Once established, plants spread by rhizomes and often form large colonies. Water-willow also reproduces by seed which are forcibly ejected from the fruiting capsule (Penfound 1940).

Waterwillow may form dense stands in shallow water areas along shorelines and occasionally interferes with recreational activities. However, it reduces erosion along shorelines and stream banks subjected to wave action and flow and provides habitat for fish and invertebrates.

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Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers

 

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