Vascular Plants of North Carolina
Account for American Water-willow - Justicia americana   (L.) Vahl
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Section 6 » Order Scrophulariales » Family Acanthaceae
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Author(L.) Vahl
DistributionPresent over much of the Coastal Plain and Piedmont, with odd gaps in the range; scarce in the mountains, with records from just three counties. Seemingly absent from the coastal areas and the southern quarter of the Coastal Plain (south of Craven and Cumberland counties). Also seemingly absent from the western Piedmont.

This is a widespread Eastern species, ranging from VT, MI, and NE south to western FL and TX. Oddly, though it ranges over essentially all of VA, there seems to be no southward extension of records into the western Piedmont or northern mountains in NC.
AbundanceFairly common to common, at least locally, in the eastern 2/3rds of the Piedmont, though locally scarce in this area (no records for well-worked Wake County). Infrequent to fairly common in the northern half of the Coastal Plain, but rare in the central portions. Rare -- oddly so -- in the mountains, as rocky stream habitats are quite common.
HabitatThis is an aquatic plant, growing in shallow water, usually with some flow, such as in rocky rivers and larger streams. It also grows in the Coastal Plain along some sandy creeks and rivers, generally along the margins.
See also Habitat Account for Piedmont and General Rocky Rivers
PhenologyBlooms from June to October, and fruits shortly after flowering.
IdentificationThis is an unusual plant, one of the few showy-flowered species that grows in rocky rivers, in often swiftly flowing waters. It is quite colonial, reaching about 2' tall; it may have branches at the base, but otherwise appears unbranched. It has numerous opposite leaves, very narrowly elliptic to linear, about 4-5" long but barely 1/2" wide, with entire margins. The flowers grow in several dense clusters, on very long and ascending stalks of a few inches; each flower is quite attractive up close, being white with fancy purple markings on the lower lip. The flower has a double lip on top, two widely flaring petals to the sides, and a bottom lip, and each flower has a spread of about 3/4". Even without the flowers, you should be able to identify the species, as it grows in dense stands with erect stems and narrow opposite leaves, but the flowers will certainly clinch it. Note, however, that most plants grow "out in the water" well away from shore, so you may need to wade in the water to study them, or study them through binoculars.
Taxonomic CommentsNone

Other Common Name(s)Water-willow
State RankS4S5
Global RankG5
State StatusW6
US Status
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