The basic taxonomy of a Portulaca plant

Let's start with some very basic taxonomy. Although the initiated among us may find this all a bit tedious, I feel it is probably necessary to get some basic botany out of the way before proceeding any further.

Pictured here is a rather generic Portulaca plant showing its main parts (click on image to enlarge).

The leaves and stems of Portulaca are generally fleshy or succulent with a mostly smooth (i.e. glabrous) surface. Plants are generally prostrate or decumbent, but some species may be upright or ascending. Some species may have prominent hairs in the leaf axils. Flowers range from being small and inconspicuous to large and showy. Flower colour may vary from species to species, but the three most common colours are pink, purple, and yellow. The roots may be tuberous or fibrous and the different species may be perennial or annual.

The seed capsule is technically called a pyxis. Here is some good information about Portulaca fruiting capsules from an Illinois Natural History website.

The pyxis is in two parts and resembles the fruiting body of a Eucalyptus tree (i.e. a "gum nut"). It comprises a lower capsule which holds the seeds and an upper lid (or operculum). The lid separates near the middle of the pyxis and falls off (dehisces) when ripe to spill out the seeds.

Parts of a Portulaca pyxis by Leo Breman (ex flickriver).

Jim Conrad's Naturalist Newsletter also illustrates this well.

Generally the seed is numerous, fine, and granular. Under magnification it is shaped a bit like a snail shell or a flattened spiral. The surface is often rough and covered in tiny stellated (or "star-like") tubercles. Seed of Portulaca oleracea (ex AcornOrganic, Steve Hurst, USDA)