Vascular Plants of North Carolina
Account for Hornleaf Riverweed - Podostemum ceratophyllum   MichauxOnly member of Podostemum in NC.
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Section 6 » Order Podostemales » Family Podostemaceae
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DistributionThroughout the Mountains and foothills, and also throughout the eastern Piedmont, yet mysteriously scarce in the central Piedmont. Barely ranges into the western edge of the Coastal Plain (Edgecombe County).

This is an Eastern species, ranging from eastern Canada south to southern GA and eastern LA. It is mostly absent from the Great Lakes states.
AbundanceFairly common to common in the Mountains and foothills. Infrequent to fairly common in the eastern Piedmont, but rare in the central Piedmont, for unknown reasons. Very rare in the western Coastal Plain.
HabitatThis is an aquatic, submerged species that grows attached to rocks within rivers and streams, usually those that are fast-flowing. It does occur on rocks in slowly-flowing waters, as well.
PhenologyFlowers from May to July, and fruits soon after flowering.
IdentificationThis is a mat-forming species, growing attached to rocks by fleshy disks. The plant is widely branched and about 3-4 inches long, composed mainly of modified leaves that are filiform (extremely narrow) and branched. The flowers are in leaf axils, but have no petals or sepals and are thus essentially green and insignificant visually. The visual aspect of the plant is a tangled mat that resemble an alga and certainly not a flowering plant, though the plants are "wiry" with the numerous filamentous leaves.
Taxonomic CommentsNone

Other Common Name(s)Rifleweed, Threadfoot, Riverweed
State RankS5
Global RankG5
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B.A. SorriePhoto taken Natick, MA, 1980s. Photo_non_NCPhoto_non_NC
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