Portulaca grandiflora, or moss rose, is an undemanding plant that thrives in situations that would spell death to most other annuals. Native to the hot, dry plains of South America, you can plant it in poor soil and will bloom beautifully all summer long, even through heat and drought.
The moss rose is an old-fashioned annual that dates to the early 19th century as a garden plant. Seeds of the plant were first collected by Dr. John Gillies (1747 to 1836) near the foot of the Andes Mountains.
Moss rose is a low-growing succulent that forms a spreading mat. Plants are only 4 to 8 inches high and cover up to 12 inches in width. The plant stores moisture in its bright green leaves, which are about an inch long and have pointed tips. The blossoms are reminiscent of roses, though only about an inch across. Flowers come in bright shades of scarlet, rosy pink, orange and yellow, and also pastels of creamy white, peach and pink. The blossoms only open when the sun is shining brightly, and close at night and on cloudy days. Though the plant dies to the ground after frost in colder areas, it sometimes reseeds. Portulaca has naturalized in some areas of Florida.
There are many cultivars, including some with double flowers. Sundance has 2-inch double flowers; Sundial has double flowers which bloom even in cooler and cloudier situations; Afternoon Delight has flowers which stay open longer during the day.
The moss rose requires full sun to flower. It does well in average or even poor soil that is sandy or rocky. Good drainage is essential. Though it is resistant to drought, it will flower more profusely with watering. Plants can be pruned for a neater appearance and to promote more flowers. No serious diseases or pests bother the moss rose.
The jewel-like flower colors brighten garden beds, rock gardens, containers or hillsides. Moss rose plants can even be tucked into the crevices of a wall or the cracks of a sidewalk or patio.
Since it requires little water, moss rose makes an excellent cover for a bed of spring bulbs. Most spring-blooming bulbs such as tulips prefer a fairly dry soil during their summer dormancy.
Good partners for the moss rose include zinnia, which enjoys the same culture and blooms in similarly bright colors. Sweet potato vine, either in lime green or deep purple, offers an attractive foil to the brilliant flowers of the moss rose. The gray tones of dusty miller also set off the portulaca's succulent leaves.
A related plant, purslane (Portulaca oleracea) has been cultivated as a food for over 2,000 years. Some portulaca species are considered weeds.