Identification: Rotala rotundifolia (Buch.-Ham. ex Roxb.) Koehne is a tropical to sub-tropical perennial plant with considerable phenotypic plasticity. The plant can grow as an obligate aquatic, with one growth form, or as a semi-aquatic with a very different growth form (heterophyllous) (Karatas et al. 2014).
The submersed aquatic leaves are thin, lanceolate, and up to 2 cm long. Leaf surfaces of submersed leaves are dark green, grey or reddish in color, underside of leaves are red or purple. Leaves are decussate (arranged in opposite pairs at right angles to those above or below). Emergent leaves are broadly ovoid (rounded) attaching directly to the stem or with a short petiole and bright-green in color. Stems are soft, succulent, dark pink or purplish in color and abundantly branched. Copious rose colored flowers are produced in dense clusters on terminal, aerial spikes, called racemes. Fruit are small capsules (1-2 mm long) that split along sides releasing viable seeds (Cook 1976; Gettys and Della Torre 2014; Karatas et al. 2014).
Emergent R. rotundifolia establishes along shorelines and into associated wetlands rarely growing more than 15 cm in height, while submersed plants grow in tight, dense colonies more than 2 meters high reaching the water surface where the plant grows to thick surface mats (Gettys and Della Torre 2014).
† Populations may not be currently present.
Ecology: Historically native to India, but has spread as far north as the Caspian Sea, where it can survive mean winter temperatures of 4°C. This species can potentially establish and flourish in many areas of the southern continental US, western states and in the tropical territories of Guam, Puerto Rico and the Virgin Islands if introduced (Ervin and White 2007).
Rotala rotundifolia is widely available through the international aquarium plant trade. Aquarium and pond plant publications note the ease of propagation with this species, recommending planting of cut or trimmed tops into suitable substrate or simply through the natural creeping growth habit of the plant.
References: (click for full references)
Burks, K.C., V.V. Vandiver, Jr., D.W. Hall, and C.C. Jacono. 2003. Rotala rotundifolia
(Lythraceae) new to Florida. SIDA, Contributions to Botany 20(4):1765-1769.
Cook, C.D.K. 1976. A revision of the genus Rotala. Boissiera 29(1):1-156.
Center for Invasive Species and Ecosystem Health. 2015. EDDMapS: Early detection and distribution mapping system. The University of Georgia, Tifton, GA. http://www.eddmaps.org.
Ervin, G.N., and R.A. White. 2007. Assessing vegetative growth potential of exotic Rotala rotundifolia (Roxb.) Koehne (roundleaf toothcup), in comparison with Alternanthera philoxeroides (Mart.) Griseb. (alligator weed), a known successful invader. Department of Biological Sciences, Mississippi State University, Mississippi State, MS.
Gettys. L. 2015. Lookalike aquatic plants. Aquatics 37(2):15-23. http://www.fapms.org/aquatics/issues/2015summer.pdf.
Gettys, L.A., and C.J. Della Torre, III. 2014. Rotala: a new aquatic invader in southern Florida. University of Florida IFAS Extension, Gainesville, FL. http://edis.ifas.ufl.edu/.
Jacono, C.C., and V.V. Vandiver. 2007. Rotala rotundifolia – purple loosestrife of the South? Aquatics 29(1):4,6,8-9. http://www.fapms.org/aquatics/issues/2007spring.pdf.
Karatas, M., M. Aasim, and M. Çiftçioglu. 2014. Adventitious shoot regeneration of roundleaf toothcup-Rotala rotundifolia [(Buch-Ham. ex Roxb) Koehne]. The Journal of Animal & Plant Sciences 24(3):838-842.
Madsen J.D. 2010. Invasive Plant Atlas of the MidSouth. Geosystems Research Institute, Mississippi State University, Starkville, MS. http://www.gri.msstate.edu/ipams/.
Reese, N.L. and R.R. Haynes. 2002. Noteworthy collections: Alabama. Castanea 67(2):216. http://www.jstor.org/stable/pdf/4034198.pdf.
University of Florida Herbarium. 2016. Florida Museum of Natural History. University of Florida, Gainesville, FL. http://www.flmnh.ufl.edu/herbarium/.
Wunderlin, R.P., and B.F. Hansen. 2008. Atlas of Florida Vascular Plants. [S. M. Landry and K. N. Campbell (application development), USF Water Institute.] Institute for Systematic Botany, University of South Florida, Tampa, FL. http://florida.plantatlas.usf.edu/.
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.