Rock-roses
What are they?
Anyone who has visited the Mediterranean region and ventured further than the beach, cannot fail to notice the warm, aromatic scents of the scrubby vegetation that clothes the nearby hills. Much of this scent - and much of the colour at flowering time - comes from the shrubby rock-roses that are abundant in the region. Most of the shrubby species have showy, pink or white flowers and highly aromatic foliage and it is these attributes that have made them popular as garden plants. In addition to these Cistus species, the members of the genus Helianthemum are lower growing, creeping subshrubs that may have yellow, pink or white flowers.
Where are they found?
The shrubby rock-roses are popular as garden plants but are native to warmer climes. Occasional plants may turn up as garden relics or throw-outs but typically succumb after a hard winter. Our one native species is a creeping plant of short turf on chalky soils.
Identification
Our native rock-rose is quite easily identified by its combination of tough, deep green leaves and brilliant yellow flowers with a mass of stamens at the centre. The shrubby rock-roses are easily identified as a group by their scented foliage and large flowers with tissue-paper thin, crumpled petals. However, identifying stray rock-roses to species can be very difficult as there has been a long history of misidentification and mislabelling in the horticultural industry and finding an accurate key to identification of garden plants is very difficult. Many plants sold as species are, in fact, hybrids and their parentage is often debatable, while the pink rock-roses are especially difficult due to taxonomic misidentifications of wild plants in the past. I shall endeavour to add the forms that are most commonly grown in cultivation in amenity areas and which may turn up in a more or less 'wild' situation, but others might appear in our region and require a wider search to enable accurate identification.
Common Rock-rose Helianthemum nummularium
Native in short turf on shallow chalk soils, mostly in the west of our region. Flowers May to September. A low, creeping subshrub with woody-based stems.
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Gum Rock-rose Cistus ladanifer
Introduced as a garden ornamental and once found beside the A14 in south-east Suffolk. Flowers May to July. A woody shrub to 2m in height. Leaves paler beneath, linear and up to 9.5cm in length; covered in a sticky, highly aromatic gum when young. Flowers white with a dark blotch at the base.
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Sage-leaved Rock-rose Cistus salviifolius
Introduced as a garden ornamental from the Mediterranean region and recently found in the coastal dunes at Holkham, where perhaps originally planted. Flowers June to August. A woody shrub to 1m in height. Leaves deeply veined and sage-like in appearance, up to 5cm in length. Flowers white.
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Pink Rock-roses Cistus spp.
Introduced as a garden ornamental and once recorded from Cambridgeshire (see following note). Flowers June to August. Woody shrubs to around 1m in height. Leaves thickly grey-downy with wavy edges and up to 6cm in length. Flowers various shades of pink.
NOTE: A number of species, hybrids and cultivars of pink-flowered rock-roses are in cultivation in the UK. In East Anglia, only 'Cistus incanus' has been recorded in the wild and just once in Cambridgeshire in 1981. Unfortunately, C. incanus is an invalid name that has been applied to a hybrid (now Cistus x incanus but sometimes also referred to as C. x pulverulentus) and also to what is now known as C. creticus, so it is unknown which plant may have been found in Cambridgeshire in the past. The photos here show Cistus creticus to represent the pink-flowered forms until a clearer picture can be established as to what might truly be at large in our region. Other forms are doubtless present in amenity plantings in urban areas.
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