Elodea nuttallii is a species of Elodea known by the common name western waterweed or Nuttall's waterweed.
Description
It is similar to its relative
E. canadensis except that the leaves taper to an acute point. It has a thin branching stem with whorls of 3–4 (exceptionally, 5) flat leaves at intervals. Some leaves are recurved and twisted, with minute teeth. It bears tiny flowers, the
stamen ones
Abscission from their stalks and floating away from the plant. It flowers from May until October.
In Europe nearly all individuals are female, only some places with male plants are known.
Distribution
This species is native to temperate North America. It has been naturalised in Europe since 1939 and in Japan since the 1960s.
[ The first European record of Elodea nuttallii was probably 1914 in England, though it had been identified wrongly as Hydrilla verticillata,][Bennet 1914, cited in Weber-Oldecop, D.W. (1977): Elodea nuttallii (Planch.) St. John, eine neue limnische Phanerogame der deutschen Flora. Archiv für Hydrobiologie 79: 397-4037] with correct identification as Elodea nuttallii occurring in 1974. It seems to have been originally naturalised in Oxfordshire in 1966, but has now spread to most of England, and many parts of lowland Wales and lowland Scotland. The first record in Ireland was in Lough Neagh in 1984, and it has now spread widely in the country.
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