Portulacas in the Southeast are annuals that have succulent leaves and stems. They are often prostrate and branched, and have small, bright flowers with a very short blooming period. The majority of Portulacas are tropical or subtropical in distribution. There are only seven species in the Southeast, with the greatest concentration occurring in Florida.
The rarest of the Southeast group is Portulaca smallii, an inhabitant of granitic flatrock communities, which was featured in an article here last November on the Mitchell Mill State Natural Area. In that article, peripheral mention was made of another Portulaca on the flatrocks and roadsides near Mitchell Mill. Thanks to a reader, Bryan’s, suggestion, the plant has now been correctly identified as Portulaca amilis , Paraguayan Purslane, an introduced species from South America. This summer, Portulaca amilis was confirmed at Mitchell Mill and the surrounding roadsides. A check of the nearby Rolesville flatrocks and of disturbed areas in eastern Wake County found only P. amilis. It tends to be found in sandy soil in disturbed areas, roadsides, fields, lawns and gardens. The photo below shows a typical colony at the Rolesville flatrocks.
In Northhampton County, which borders Virginia, Portulaca amilis is a common lawn weed. It also appears in large colonies along the walkways north of the Roanoke River, as seen below.
The flowers of P. amilis are an intense, deep pink, very striking and attractive. The flowers bloom for only a single day and only for a few hours. Otherwise, they would be a desirable addition to a garden. As seen in the close up below, the flowers have many stamens (tipped with yellow pollen) and the stigmas have multiple branches (seen in the center of the flower).
Below are seed capsules opened to show the typical black, shiny, round seeds of P. amilis.
The native range of Portulaca amilis is widespread in South America, including parts of Brazil, Paraguay, Uruguay, and Argentina. It first arrived in the United States in North Carolina, an unusual occurrence, particularly since the first reports were inland, and not at the coast. In 1981, Judd and Wunderlin reported that the earliest herbarium collection date they had seen was in 1956 from Harnett County, which is in central North Carolina. Later, in 1985 , Matthews and Levins reported finding what remains today the earliest collection : 1932 in Robeson County, North Carolina, on the border with South Carolina. They also hypothesized that P. amilis seeds may have “…hitchhiked from South America following a military exercise…” and become established at Ft. Bragg and other military bases near Fayetteville, North Carolina. From there it has spread north to Virginia, south to Florida and west to Louisiana.
Thanks again to Bryan for calling attention to this interesting history in his comments.
First Report of Portulaca amilis (Portulacaceae) in the United States, Walter S. Judd and Richard P. Wunderlin, SIDA, Contributions to Botany, Vol 9, No 2 (November 1981), pp. 135-138
The Genus Portulaca in the Southeastern United States. James F. Matthews and Patricia A. Levins, Castanea, Vol 50, No 2 (June, 1985), pp. 96-104