Echinodorus scaber

Plants under the name Echinodorus scaber have long been known in the aquarium hobby. However, they probably are not E. scaber in the original sense.

Echinodorus scaber was described as a species by Karel Rataj in 1969, but is regarded by Haynes & Holm-Nielsen (1994)¹ as a subspecies of E. macrophyllus (Echinodorus macrophyllus ssp. scaber). Samuli Lehtonen (2008)² argues, using analyses of morphological and DNA data, that E. scaber is in fact a distinct species that can be separated from E. macrophyllus. He also described Echinodorus plants from western Amazonia (Ecuador, Peru, Bolivia) that are closely related to E. scaber as a new species (Echinodorus emersus).²

Echinodorus scaber is distributed in Central America (southern Nicaragua) and parts of tropical South America, where it colonises wet depressions in flooded savannas.² It is a large marsh plant with heart-shaped leaves and branched, erect inflorescences up to 3 m tall, resembling other large-growing species such as Echinodorus floribundus and E. macrophyllus. The petioles are 30-150 cm long, 5-10 mm thick, round in cross-section, longitudinally grooved and roughly hairy (covered with warts and stellate hairs). The leaf blades are ovate, 9-30 cm long and 5-15 cm wide. In pressed leaves, no translucent markings (laticifers) are visible in transmitted light. A characteristic feature of E. scaber is the relatively small flowers with petals only about 4 x 3 mm in size, which are bent back soon after the flower opens and do not overlap, as well as 13 to 18 stamens. The nutlets are 2.3 to 3.3 mm long and have 5-6 ribs on each side and 0-2 round glands between the ribs. The closest related species, Echinodorus emersus, differs from E. scaber among other things in unbranched or little-branched inflorescences, distinctly larger flowers with overlapping, non-reflexed petals, a greater number of stamens, and nutlets without glands.²

It is unclear whether the true Echinodorus scaber is cultivated as an aquarium plant. In the "Neue Revision der Gattung Echinodorus" by Karel Rataj (2004)³, a cultivated plant called E. scaber is illustrated on p. 116, which has roundish, deeply heart-shaped emersed leaves and large flowers 28 mm wide. One of the photos shows a plant that has been growing submersed for a year, and according to Rataj, young submersed specimens are often attractively coloured red. Photos of this plant can also be seen on www.aquapage.eu⁴. According to Lehtonen (2008), however, this Echinodorus does not belong to E. scaber, because the flowers are much larger than stated in the original description of this species. We have no information on which species this aquarium plant belongs to instead.