A moss rose is a flowering succulent plant, often grown as an annual ornamental. It is also known by the names rose moss and portulaca, and portulaca is also the name for the genus it belongs to. This low-growing plant bears small, rose-like flowers that come in a variety of colors, often red or white. Like other succulents, it has fleshy leaves that store water. Its scientific name is Portulaca grandiflora.
The plant is usually low-growing and often has a sprawling or trailing habit, though it sometimes grows upright. The cylindrical stems are also somewhat fleshy, and grow to lengths of about 6 to 10 inches (15-25 cm). The leaves may be rounded or flat, usually about 1 inch (3 cm) long at most. Moss roses are grown primarily for their small, cupped, rose-like blossoms, which come in a variety of colors. Common colors include a deep red as well as pink, white, and green.
Germinating and growing best in warm and hot weather, the moss rose thrives in sandy or below average soil. As the plants retain some water, moss roses can tolerate dry periods and require minimal watering. Plants are often grown in full sun in dry conditions, and can be planted in the ground or in containers. Moss rose flowers close at night and are open only during the day. The leaves behave similarly, closing in toward the stems after sunset.
Moss roses are typically grown from seed in new beds and containers. This is usually done in midspring, after which the plants grow quickly. After flowering, seed can be collected for use in the next year. The moss rose produces a large amount of tiny seeds, and often self-sows in the ground or in containers. If the plants are grown in the same place year after year, collecting or buying seeds probably won't be necessary.
The moss rose is related to common purslane, another low-growing succulent that is often considered a weed. Purslane is frequently found naturally growing between the cracks in walls, sidewalks, and garden paths. Moss rose also thrives in these places and can be used in such spaces as a more attractive alternative.
Although the term moss rose can refer to a flower of the rose family, Rosa centifolia, most authorities use the term to refer to P. grandiflora. R. centifolia is also called the Provencal or cabbage rose. A true rose, R. centifolia produces cupped, often pink flowers noted for their fragrance.