Rock Rose (Helianthemum nummularium)
Rock rose, the remedy for those suffering from terror, is made by the sun method.
The genus name comes from the Greek helios meaning sun and anthemon meaning flower. In the wild, flowers of Helianthemum nummalarium, or common rock rose, are yellow although cultivated varieties can range from white to deep red. In the South-east of the UK, it grows in chalky or limestone-rich soils, which are alkaline, but in Scotland it can grow in much more acidic soils.
The plant only opens its flowers one at a time, in fine weather, but although its name suggests it is a sun loving plant, it always directs them away from the sun. Its stamens are sensitive to movement and react to dampness. As a pollinating insect brushes the anther, the stamens drop pollen onto its fur and start to turn to the side – this makes it easier for the pistil in the middle of the flower to touch the next insect and improves its chances of receiving pollen from a neighbouring flower on its stigma.
The genus is part of the rock rose family (Cistaceae) and contains plants sometimes known as frostweeds. The name frostweed is used for a number of plants including Verbesina virginica (white crownbeard), Helianthemum canadense (longbranch frostweed) and Helianthemum bicknellii (hoary frostweed) due to their ability to produce so-called frost flowers – caused by water freezing in the stems. As it expands, it pushes through the stem and, as more water follows, the ice is pushed out, curling into shapes which can resemble flowers. For more information on frost flowers and how they form, check out youtube.
Longbranch frostweed was used medicinally to treat secondary syphilis, as an astringent, alterative and tonic and to treat scrofula (usually a swelling of the lymph nodes in the neck caused by tuberculosis). An oil obtained from the plant was used to treat cancer.
Another genus in the rock rose family is Cistus and an important resin, known as labdanum, is obtained from two species, Cistus creticus and Cistus ladanifer. The leaves are covered in glandular hairs and goats and sheep eating the plants become covered in the resin. This was combed off their coats and sold. The resin is still used today in perfumery although now it is obtained directly from the plants by treating with hot alkaline solution, followed by steam distillation to produce the oil. The scent resembles incense and ambergris and labdanum is sometimes used as an alternative to ambergris.
The oil contains over 300 constituents, the most abundant of these is ledene (also known as viridiflorene). Ledene has potential use for the treatment of ocular Demodex (eyelash mites).
Examples of a class of chemical compounds called labdanes were first identified from labdanum. Some labdanes have antibacterial, antifungal, antiprotozoal or anti-inflammatory activities. Traditionally, labdanum was used as an expectorant, an emmenagogue and in plasters.