How to Grow Moss Rose Flowers (Portulaca)

By Julie Christensen

Most gardeners have a place in their garden where almost nothing grows. You know the spot — soil the consistency of sugar, blazing heat and limited access to water. Moss rose, a member of the succulent family, is the solution to this gardening eyesore. These tough little plants grow in even the harshest conditions.

Interestingly, they were first developed by an Englishman, most certainly in conditions that could hardly be called dry. Portulacas were first discovered in Argentina by Dr. John Gillies. They grew in sandy, infertile soil at the base of the Andes Mountains. Dr. Gillies was entranced with the plants’ low-lying growth and prolific blooms.

Moss roses have thick, padded leaves that store water, allowing them to tolerate drought conditions. They’re often used in rock gardens or in xeriscapes. But, don’t think you have to live in the desert to grow these. They grow from U.S. Department of Agriculture plant hardiness zone 2 through 11. They don’t grow particularly well in rainy climates, and they won’t bloom on cloudy, rainy days.

Moss roses are annual flowers, but they self-sow readily and may come up year after year with little help from you. The flowers bloom in a profusion of colors, from yellow to pink to purple. The original plants bloomed only in the morning and closed by midday. Newer varieties have double, rose-like petals and stay open all day. Moss roses are compact plants, rarely growing taller than 6 inches. Their spread is only about 12 inches wide.

Growing Moss Rose

Most gardeners grow moss rose from nursery transplants or cuttings, but you can also start the plants from seed. Start them indoors four weeks before the last frost or sow them directly outdoors in warm weather. Cover them with a thin layer of soil and keep the soil evenly moist until the seeds germinate. Moss roses germinate best when soil temperatures are between 75 and 85 degrees. Moss roses have fragile roots so transplant them carefully.

Although moss roses tolerate dry, infertile soil, they’ll grow better with a little care. Water them every week or so during dry conditions and amend the soil with compost prior to planting. Moss roses produce prolific black seeds, which can slow flowering. If this happens, shear the plants back to encourage a new flush of blooms.

Moss Rose Pests and Diseases

Moss roses are low-maintenance plants that thrive on neglect. Most diseases are actually caused, in part, by too much care. Root rots, for example, are exacerbated by wet soils. Planting moss roses in dry, well-draining soil usually solves this problem. White rust sometimes infects moss roses, but it is rarely serious. To keep the plants healthy, water infrequently, using drip systems instead of overhead sprinklers. Water first thing in the morning so the leaves dry quickly. Remove and discard any infected plants.

Aphids occasionally infest moss roses, although the damage is rarely severe. Aphids are tiny and hard to spot, but they leave several tell-tale signs, including a sticky substance called honeydew and a black sooty growth, which is actually fungus attracted to the honeydew. Aphids have piercing mouth parts and suck the sap from moss roses. They generally move on within a few weeks and several beneficial insects prey on them. In general, they need no treatment, although you could spray the plants with a stream of water to dislodge them.

Varieties of Moss Rose

‘Sundance’ is a favorite cultivar because it has double flowers and blooms all day.

Try ‘Calypso,’ which produces flowers in a variety of colors.

Learn more at these great web sites.

Better Homes and Gardens has a page about Moss Rose, with a good guide to varieties.

Floridata also has an informative page that covers moss rose in great detail.

YouTube has a great University of Illinois extension service video about growing portulacas in containers or the garden.

When she’s not writing about gardening, food and canning, Julie Christensen enjoys spending time in her garden, which includes perennials, vegetables and fruit trees. She’s written hundreds of gardening articles for the Gardening Channel, Garden Guides and San Francisco Gate, as well as several e-books.