Native to hot, dry plans of southern Brazil, northern Argentina and Uruguay, moss rose (Portulaca grandiflora) is also known by the names "sun plant," or "rose moss." Spreading stems with thing fleshy leaves are donned by bright colored flowers in warm sunny weather. On cloudy days these flower may not open at all. Grow moss rose in any sunny garden spot with a fast-draining soil, that is slightly moist when temperatures are hot, drier when cool.
Moss rose is an annual plant, meaning it will germinate from seed (tiny capsules), grow, bloom and die all within one growing season. It reseeds itself into the landscape, with new plants sprouting when conditions are warm at the beginning of the next growing season. Bits of stem or leaf may root when left in contact with warm, damp soil. According to Floridata, moss rose is one of the few annual succulent plants in the world.
There are over 100 different species of semi-succulent plants in the botanical genus Portulaca. Portulaca grandiflora is specific, appropriate only for those with red stems and clusters of cylindrical leaves according to the American Horticultural Society's A-Z Encyclopedia of Garden Plants." All are members of the purslane family, Portulacaceae.
Moss rose is an angiosperm or flowering plant. Even though the plant's stems and leaves seem basic in vein pattern and structure, it is considered a dicotyledon (dicot), meaning its seeds germinate with two leaves, according to the Description Language for Taxonomy website.
Ornamental in appearance, moss roses have been bred extensively by horticulturists for use as bedding annuals. Many cultivated varieties (cultivars) exist today, some discussed as general hybrids or as a series, a collection of similar varieties. Examples include the Minilaca hybrids which remain compact at maturity with double-form blossoms and Sundance hybrids which were bred to display larger-sized blooms. Names of series include Calypso and Sundial, which tend to open blooms even on cloudy days or when summer temperatures aren't warm according to "A-Z Encyclopedia of Garden Plants."
Sometimes moss rose is misleading called "flowering purslane." Purslane typically refers to the ornamental species Portulaca oleracea, which is grown as an edible leaf vegetable in tropical areas. Many modern cultivars of ornamantal purslane display bright showy flowers because they are the result of complex hybridization according to Learn2Grow. Purslane also is a general name assigned to any of several Portulaca species with no ornamental value that grow as weeds.