Potamogeton epihydrus
| Potamogeton epihydrus | |
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| Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Alismatales |
| Family: | Potamogetonaceae |
| Genus: | Potamogeton |
| Species: | P. epihydrus |
| Binomial name | |
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Potamogeton epihydrus Raf. |
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| Synonyms | |
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Potamogeton epihydrus is a perennial aquatic plant known by the common name ribbonleaf pondweed, Nuttall's pondweed (not to be confused with Elodea nuttallii) or in Britain and Ireland American pondweed. It is native to much of North America, where it grows in water bodies such as ponds, lakes, ditches, and slow-moving streams.
This is a perennial, rhizomatous herb producing narrow, compressed, unspotted stems to a maximum length of about 1 m. The stems are either unbranched or sparingly branched. It has two types of leaf. The submersed leaves are sessile 5-25 cm long and 0.1-1 cm wide, translucent, linear in shape and ribbonlike, red-brown to light green in colour with a blunt to acute tip. The floating leaves are similar to the floating leaves of other Potamogeton, petiolate and opaque, up to 8 centimeters long and 3 wide.
The inflorescence is a small spike of flowers that arises from the water on a peduncle 1.5-5 (rarely up to 16) cm.
This is a diploid species, with 2n = 26. Hybrids have been described with P. gramineus, P. nodosus (P. × subsessilis Hagstrom), P. bicupulatus (P. × aemulans Z. Kaplan, Hellq. and Fehrer), and P. perfoliatus (P. × versicolor Z. Kaplan, Hellq. and Fehrer).
Potamogeton epihydrus (meaning 'on the water surface') was described by Rafinesque in 1808, one of the earlier North American species to be named.
DNA analysis indicates that, despite the presence of floating leaves P. epihydrus is closely related to P. tennesseensis. These two are within the basal part of the large clade of fine-leaved pondweeds including P. diversifolius, P. pusillus and P. compressus.
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