Synonyms: Ludwigia pilosa (erroneous)
Light Needs: High
Plant Structure: Stem
Region: North America
Location: USA - Massachusetts to Texas
Size: Stem width - five inches
Growth Rate: Moderate
Can Be Grown Emersed: Yes
Ludwigia sphaerocarpa is one of the fourteen species of polyploid Ludwigia placed in section Microcarpium, all but two of which are endemic to the United States. The familiar L. glandulosa also belongs to this section, as does the equally suitable L. alata and several others which have yet to achieve widespread distribution within culture. L. sphaerocarpa is found in a variety of moist and wet coastal plain habitats such as pond margins and wet ditches ranging from Massachusetts to eastern Texas. Disjunct populations are found in central Tennessee and along the southern part of Lake Michigan.
Of particular interest to aquarists, of course, is the appearance of cultivated plants. Nearly all species of Ludwigia in section Microcarpium grow stolons that grow along the ground or below water and eventually transition into more adult plants. Stolon leaves in L. sphaerocarpa are quite different in appearance from mature plants. In this case, they are rounded and with distinct hydathodal teeth, which are the end points of a mechanism used to transport nutrients through the leaves. It is these leaves, rather than those of the mature plant, that are grown in submersed culture. In wild plants, the stolon leaves are somewhat widely spaced, but in submersed cultivated specimens, a very compact plant forms.
Ludwigia sphaerocarpa was introduced to the aquarium hobby by aquarists from Houston, Texas in 2008 and was, until recently, thought to be the related L. pilosa. It has already proven to be quite popular. Unlike previously cultivated Ludwigia species, L. sphaerocarpa is suited for the foreground and middle areas of aquascapes. With care and some careful pruning, strikingly attractive, mounded reddish-orange crowns can form. Stems that have become established can grow to around five inches wide from leaf tip to leaf tip, so some room is definitely required. If any become too large, they may be removed, and in a short time, several new, smaller shoots will form. Not small enough to form the basis of a foreground, it can instead compliment smaller species, which can help cover its less attractive lower portions. To maintain low growth and to preserve the health of the plant itself, strong lighting and a lack of shade are absolutely required; otherwise, plants remain green and grow much more slowly. If such conditions persist, the plants may eventually die. Although L. sphaerocarpa is probably not a plant for beginners, it will certainly have a lasting place in aquarium culture.
Sources used/further reading:
Peng, C. (1989). The Systematics and Evolution of Ludwigia Sect. Microcarpium (Onagraceae). Annals of the Missouri Botanical Garden, 76, 221-302.
Photo #1: Submersed US and International Copyright 2011 by Tim Gross All Rights Reserved