Vallisneria spiralis

Vallisneria spiralis is one of the "classic" aquarium plants, known in the hobby since the beginnings of aquaristics. In nature it is distributed in stagnant and flowing waters in Africa, Asia and the warmer regions of Europe (e.g. Italy). Its species name "spiralis" does not refer to its leaf form but to its flower stalk, which starts spiralling after the female flower has withered (as it does in all Vallisneria species). Thus the infrutescence is drawn downward.
The plants sold as V. spiralis in trade can grow to very different lengths. However, in most cases plants with smooth (not spiralling) relatively narrow leaves are labeled V. spiralis. So-called "V. spiralis" imported from Malaysia have been identified as Vallisneria denseserrulata, a species native to Asia, recently differentiated from V. spiralis but very hard to know apart without flowers.

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