The sun rose is one of about 110 varieties in the genus Helianthemum. They are creeping, shrubby plants, most growing one foot in height or less. The flowers are small and dainty, resembling roses. The plants form a mat as they spread, and flowers cover the plants for several weeks during the early summer. Sun roses are perennials, returning each year with showy vigor. Sun rose plants have many different colors of flowers, ranging from pastel pink to raspberry, bright red and coppery orange.
Helianthemum are native to dry European grasslands. They are known by common names such as as sun rose, rock rose and frostweed. The common names are all descriptive. Sun rose plants like hot, sunny areas, and they prefer dry rock gardens or rocky soil. The leaves on many varieties are silvery-gray, with a frosty appearance.
Sun roses are used in rock gardens and as border plants along driveways. They grow well near rocky paving stones and walkways, where they form low mounds of flowers that require little care. Sun roses are lovely along retaining walls, where they will tumble over the edge in a mass of blooms. They will cover barren, rocky slopes where other vegetation would struggle.
Sun roses are interesting plants in the winter garden, because they retain their leaves throughout the winter. The old leaves are shed as new ones grow in the spring.
Sun roses are easily grown from seed. Start the seeds early in the spring for later transplanting into the garden. Seed should be planted on the surface of the soil. Germination requires up to three weeks, and the baby plants should be six to seven weeks old when they are set out permanently. If the plants were started in a cold frame or greenhouse, they need to be acclimated to the outdoor conditions for a few days before setting them out permanently. Wait until frost danger has passed before transplanting young sun roses.
Seeds may also be sown directly outdoors either in the late fall or early spring after the danger of frost.
Established mounds of sun roses may be divided every two or three years. Spring is the best time to make divisions. Sun roses can also be rooted from cuttings.
Sun roses prefer poor to mildly fertile soil in full sun. Some varieties will tolerate partial shade if the soil is dry and not overly fertile. Transplant new plants or divisions at the same depth they were previously growing. Water the transplants at planting time, and sparingly thereafter. Sun roses are excellent additions to xeriscape gardens due to their drought tolerance.
An average water requirement for helianthemum is about 3/4 inch of water every two weeks. Established sun roses may be pruned early in the spring to reduce woody growth and to encourage new growth. In the summer after the plants bloom, they may be pruned back by about one-third to remove dead flower heads and to encourage new growth. Some varieties may bloom again after a summer pruning.
Sun roses are not bothered by diseases or insect pests. Once established, they are hardy and long-lived, seeming to thrive on neglect.