Vascular Plants of North Carolina
Account for Horsetail Crowngrass - Paspalum fluitans   (Elliott) Kunth
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Section 5 » Order Cyperales » Family Poaceae
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Author(Elliott) Kunth
DistributionMostly lower Piedmont and inner northern Coastal Plain. Known from the Cape Fear, Eno, Meherrin, Neuse, and Roanoke river systems.

MD to KS, south to FL and TX; tropical America.
AbundanceRare to uncommon; populations are locally distributed. Though the NCNHP database lists only 7 records and just 3 extant, it is likely the species is under-collected, especially in the Roanoke River system, as there are numerous VA records. Their S1 State Rank does fit their database, but the website editors feel that S2 is a more reasonable rank, considering the number of counties with specimens (10+). This is a Significantly Rare species. In the Amazon basin this species forms enormous colonies, eventually breaking off and floating downstream as huge rafts that support other plants, insects, birds, etc.
HabitatBrownwater river shores, mud bars, and in very shallow water. Also backup channels and depressions in brownwater floodplain forests.
See also Habitat Account for General River Bars and Sparsely Vegetated Shorelines
PhenologyFlowering and fruiting September-October.
IdentificationThis is one of only two NC crowngrasses in which the inflorescence rachis has broad wings that cover or hide the spikelets. The other is P. dissectum, which differs in its leaf blades being less than 6 mm wide (vs. greater than 6 mm wide in P. fluitans). It also is one of the few Paspalum species in NC with many inflorescence branches (20+).
Taxonomic CommentsA synonym is P. repens.

Paspalum is a genus of more than 300 species, found mostly in the New World. The genus is quite easily identified by the neat row of spikelets along each side of a flattened rachis (inflorescence branch), and also by the hemispherical outline of each spikelet. In some species there are only 2 such inflorescence branches, paired at the stem summit; in most of our species there are 3-4 branches; and in a few there may be many. Keys ask whether spikelets are paired or not -- that is, at each node on each side of the rachis there are pairs of spikelets on tiny stalklets. Care must be taken with a hand lens to make sure there are 2 stalklets at each node, as frequently one of the two spikelets will not grow. Non-paired or single spikelets will clearly have only a single stalklet per node.
Other Common Name(s)Water Paspalum, Horsetail Paspalum
State RankS1 [S2]
Global RankG5
State StatusSR-P
US Status
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