Ludwigia sphaerocarpa

Ludwigia sphaerocarpa is a marsh plant distributed in the southern US states that colonises various wet habitats.¹ As an aquarium plant it has been known only since 2008 and until recently (about 2012) only in the USA. Some aquarists in Europe are already cultivating the plant, but it is still largely unknown here.²

In the USA the plant was at first mistakenly thought to be Ludwigia pilosa . Aquarists in Texas collected the plant in the wild, found that it is suitable as an aquarium plant and looks splendid submersed, and passed it on under the name L. pilosa. Later, Cavan Allen (USA) informed the forum www.aquaticplantcentral.com that it had been identified as Ludwigia sphaerocarpa on the basis of its floral characteristics. True L. pilosa is a similar, closely related species that is probably not (yet) cultivated in aquariums.

Ludwigia sphaerocarpa and L. pilosa belong to the Ludwigia section Microcarpium, as does L. glandulosa. Some further species from this section have also already proved suitable for aquariums (information from Cavan Allen¹).

In the terrestrial form Ludwigia sphaerocarpa has oblong leaves and then looks rather inconspicuous. At the base the plant develops creeping or water-floating shoots (stolons) that bear obovate to roundish, toothed leaves. The leaf teeth have tiny openings, so-called hydathodes, at the tip. Almost all other species of the section Microcarpium also form stolons.¹

The submersed shoots of L. sphaerocarpa that develop in the aquarium correspond to these stolons, but are more compact and densely leaved, almost rosette-like. This makes L. sphaerocarpa very different from other aquarium Ludwigias. Depending on the light intensity, the submersed leaves are coloured green to splendidly reddish orange, similar to Ludwigia inclinata var. verticillata 'Cuba'.¹