Phylum: Magnoliophyta - Class: Equisetopsida - Order: Malvales - Family: Cistaceae
Common Rock-rose is a perennial, low-growing and sometimes almost prostrate wildflower.
This spreading plant grows to about 30cm in height. Its woody reddish stems branch and are variably hairy. The yellow flowers, each with five touching or overlapping crinkled petals, open in sunshine and close up at night - hence the genus name Helianthemum, which means 'sun flower'. The flowers are typically 20 to 25mm across, while the lanceolate leaves are evergreen and 5 to 20mm long and have a few hairs on the upper surfaces while their undersidesare white and densely covered in fine woolly hairs.
In Britain and Ireland this wildflower is nearly always associated with dry alkaline soils.
In Britain and Ireland, Common Rock-rose is common and widespread wherever there is chalky grassland or limestone cliffs and rocky areas. It is particularly common in southern England and in parts of Scotland. On mainland Europe this member of the family Cistaceae occurs from Scandinavia right down to the Mediterranean as well as in parts of North Africa.
In Britain and Ireland Common Rock-rose produces flowers from May through to September.
The specific epithet nummularium means 'shaped like a coin'.
Hoary Rock-rose Helianthemum oelandicum is also found mainly in limestone and chalk regions of Britain and Ireland; it starts flowering a month or so earlier than Common Rock-rose and its flowers are usually much smaller than those of Common Rock-rose.
In the Mediterranean region of Europe, Spotted Rock-rose Tuberaria guttata is very common; it has yellow petals with distinctive red patches at their bases.
The Common Rock-rose specimens shown here were photographed in southern France during June.
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