Myriophyllum hippuroides

A milfoil has long been known in the aquarium hobby as Myriophyllum hippuroides, and it often enters the trade under this name. According to Kasselmann (2010), however, this plant is wrongly identified and actually belongs to the species Myriophyllum pinnatum. Accordingly, true M. hippuroides is not cultivated as an aquarium plant, or at least there is apparently no evidence of it. Therefore no information on the cultivation requirements of M. hippuroides can be given here, even though this species can presumably be kept in aquariums just as well as M. pinnatum.

True M. hippuroides is distributed in western and central North America. It colonises lakes, ponds, ditches and small streams there. In its submersed form, M. hippuroides can be confused with its relatives M. pinnatum and M. heterophyllum, which originate from eastern North America.

The submersed shoots have feather-like leaves that are arranged on the stem in often irregular whorls of 4 to 5 and are 2 to 5 cm long. The underwater leaves have 6 to 20 opposite pairs of pinnae.

The stem is yellowish green, richly branched and grows to at least one metre in length.

The plant also forms robust flowering shoots, 3 to 12 cm long, that project out of the water. The emersed leaves on these shoots are whorled, overtop the flowers and are 5 to 10 mm long and 1 to 2 mm wide. The leaf margin is smooth to toothed, but not deeply incised.