Helianthemum is a genus of plants that includes around 110 species of evergreen and semi-evergreen shrubs belonging to the Cistaceae family. Also known as rock rose, sunrose, and rushrose, Helianthemum can be found in America, Europe, and northern Africa. The Mediterranean region, however, is considered its center of diversity.
These plants are often cultivated as garden landscaping plants. A majority of plants in this genus that are used in gardens tend to be hybrids of the H. Apenninum and H. Nummularium species. H. Apenninum is endemic in Europe, the Mediterranean, and Asia Minor, while H. Nummularium species are usually found in Armenia and the Caucasus and Atlas Mountains.
The leaves of these plants are like two ovals, around 1.5 inches (4 cm) in length and 1 inch (2 cm) in width, placed opposite each other. These plants are normally glossy green to grey-green in color. Helianthemum’s flowers also span around 1 to 1.5 inches (2 to 4 cm) in diameter. They have five petals that are usually white or yellow. In some species, the petals are a bit pinkish, while in other species the inner center is usually bright yellow to attract pollinating insects. On the other hand, cultivars are able to produce a broader range of color, from salmon pink to dark red.
As a member of the food chain, the species of this genus are fed on by the larvae of Lepidopteras, more particularly, the large grizzled skipper. Other organisms that feed on some species of Helianthemum are Coleophora case-bearers and Bucculatricid leaf-miners, which feed only on the species Helianthemum sessiliflorum. Bucculatricid leaf-miners, Coleophor case-bearers, and the large grizzled skipper all belong to the moth family.
Many species of Helianthemum, including hybrids, are grown as ornamental plants and are often used in rock gardens as edging plants. Landscape artists often consider their bright colors when placing them on sunny banks and borders during May and early June. They can also be used as ground cover because of their matting habit and evergreen nature. Some people also use sunroses as wall draping or let the plant creep around small rocks.
Landscape artists and gardening enthusiasts tend to find these plants low maintenance. They are sun-loving and do not require too much watering. This is because they naturally grow in sunny rockeries and dry lands. Most plants that belong in this genus favor full sun exposure and well-drained soil or limestone. They can tolerate the fiercest of droughts, even producing more flowers in hotter climates.