The attractive, purple-flowered Maltese rock-centaury (Cheirolophus crassifolius) is the national plant of Malta (1)(2). It is a perennial shrub with smooth, fleshy, spatula-shaped leaves (2). The flower heads are borne singly on stalks, with each being made up of numerous, small, individual purple flowers, or ‘florets’, that are tubular in shape (2). The modified leaves around the flower head, called bracts, are smooth and lacking in spines (2).
The seeds of the Maltese rock-centaury are equipped with a parachute-like structure that aids wind dispersal (2).
The Maltese rock-centaury belongs to the Compositae family (also known as the Asteraceae), which is one of the largest families of flowering plants, containing around 25,000 species. The Compositae are easily recognised by their inflorescence, which is made up of many tiny flowers or ‘florets’ (3). The clusters of tiny flowers are surrounded by a whorl of specialised leaves, called ‘bracts’, which often resemble petals. The whole structure looks like a single flower, and is often confused as such (4).
Although there is little specific information available on the biology of the Maltese rock-centaury, it is known to be a long-lived species that flowers from May to July (2).
As its name suggests, the Maltese rock-centaury is endemic to Malta (2). It grows on the north-western and southern cliffs of the main island of Malta, and also on the smaller islands of Gozo and Fungus Rock (1).
With an estimated population of just a thousand individuals, the Maltese rock-centaury faces a number of threats (1). It has a restricted range and therefore is vulnerable to habitat degradation from nearby quarrying activities. It is also known to be at risk from human disturbance, particularly where it grows in more accessible areas (1)(2).
The Maltese rock-centaury is also threatened by invasive plant species, and is believed to be at risk from attacks by an unidentified moth larva(2).
The Maltese rock-centaury is legally protected by its listing on the EC Habitats Directive as a priority species, affording this species some protection (1)(3). The cliffs of Malta, and some on Gozo, are protected locally with access only granted for scientific purposes (2). Fungus Rock is protected as a nature reserve (2). This species has also been cultivated therefore providing a stock for potential future reintroduction (2).
Future conservation priorities for the Maltese rock-centaury include the careful management and protection of its habitat and the designation of additional protected cliffs on the island of Gozo (2). Further research is also needed in order to identify the causes of the Maltese rock-centaury population decline and implement preventative measures for the future (2).
de Montmollin, B. and Strahm, W. (Eds.) (2005) The Top 50 Mediterranean Island Plants: Wild Plants at the Brink of Extinction, and What is Needed to Save Them. IUCN/SSC Mediterranean Islands Plant Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at: http://data.iucn.org/themes/ssc/our_work/plants/t50_e.pdf
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