Portulaca smallii (Small’s Purslane) is a rare, protected plant, endemic to the thin soils of granite flatrocks and outcrops in the Piedmont regions of Virginia, North Carolina, South Carolina (a single site) and Georgia. The Mitchell Mill State Natural Area contains the largest granitic flatrock community in North Carolina, and Portulaca smallii is present there, scattered through much of the flatrocks. At Mitchell Mill, P. smallii is found only in a restricted zone, in thin soil between the open rock and the deeper soils and background vegetation behind it. In other sites, it has been reported to colonize nearby fields and disturbed areas, but this has not been seen at Mitchell Mill.
P. smallii is a succulent summer annual, a member of the large Purslane family, the Portulacaceae. The photo below is of an aggregation of plants as they would appear to a passer by. Notice the close proximity to the exposed rock and the thinness of the soil.
Closer views of individual plants are illustrated below.
The seeds of P. smallii primarily germinate in spring and early summer, and flowering often follows closely in a month or so. The flowers are usually a pale pink, and can be so pale as to appear white at times. The flowers open for only a short period around noon, and may remain closed all day when the skies are dark with clouds. The flowers can self-pollinate, which is useful when the period for pollinators to enter the flower is so narrow. A typical flower blooming in July follows.
A wider view shows the leaf shape, which is generally lance-like in outline, and rounded and cylindrical in shape.
There is another, closely related portulaca at Mitchell Mill – Portulaca pilosa (Pink Purslane, or Rose-flowered Purslane). This plant is common and widespread in the area, and also grows on the flatrock soils, sometimes directly beside P. smallii.
Portulaca pilosa can be distinguished from Portulaca smallii by its larger, dark pink flowers, and its flatter, wider leaves that often appear like the blades of a fan.
Although the preponderance of germination takes place in spring and summer, P. smallii seeds are capable of germinating throughout the growing period. Below are photos of seedlings estimated to have germinated in late August or September. The scrolling vein patterns stand out clearly in these tiny plants.
Both portulaca species at Mitchell Mill begin to decline in October and by Thanksgiving, most plants have disappeared completely or there is only a remnant stem or dead leaves. Pictured below are several plants that have expired but are still relatively well preserved in late November. Portulaca smallii is directly below, followed by Portulaca pilosa.
Portulaca smallii is a protected plant in North Carolina: Status – Threatened (T); Rank -Imperiled (S2); Global Rank – Vulnerable (G3). Although most plants are found on granite outcrops and flatrocks, they have also been reported on diabase flatrock.