Daniel recently wrote about Quercus robur, but it’s been some time since I wrote about a species native to Europe, so today I’ve chosen Centaurea benedicta (formerly Cnicus benedictus) as the topic. Perhaps best known (in English) as blessed thistle, its importance as a historical medicine makes an interesting contrast with the widespread notion of it as an invasive weed (where it has been introduced).
A member of the Asteraceae, the genus Centaurea contains approximately 250 species. According to Pliny, the medicinal properties of this genus were discovered by Chiron, a mythical centaur. The specific epithet benedicta is derived from Latin, meaning “to be blessed”. The informal term “thistle” could be applied specifically to species in the genus Cirsium, but it is also used for a number of related species in the Asteraceae with spinose leaves and leaf-like organs. Wikipedia describes Centaurea benedicta as “thistle-like”, as it only somewhat shares the appearance of the typical purple-flowered thistle. Another example of a Cirsium relative is milk thistle, featured on Botany Photo of the Day in 2006. Always be cautious with common names (and thistles, for that matter)!
As shown in today’s photo, the yellow inflorescences of the summer-blooming blessed thistle are at the apex of stems. Subtending these flowering heads are a set of spiny pinnatifid phyllaries. Like many (all?) other species of Centaurea, Centaurea benedicta is a species of sunny, dry environments.
Blessed thistle is native to the centre of diversity for the genus, the Mediterranean region of Europe. Its native range extends eastward to Iran. Like many other species, it now occurs in areas of the world where it isn’t native. At these locations, it is often considered a noxious weed (see its appearance in the Flora of North America and Flora of China as examples of its non-native range). Mediterranean-type ecosystems, such as those where Centaurea benedicta natively occurs, are extremely biodiverse areas that recall fond memories from the countless hours I’ve spent roaming their dry scrublands watching birds. According to the IUCN, the total vascular plant flora of Mediterranean-Type Ecosystems accounts for roughly 20% of the world’s plant species, yet only covers just over 2% of the Earth’s terrestrial surface. These ecosystems are widely dispersed, occurring in southwestern and southern Australia, central Chile, California and northern Baja California, the Western Cape of South Africa, and of course, the namesake lands surrounding the Mediterranean Sea. All are designated as biodiversity hotspots.
Throughout the middle ages, blessed thistle was popularly seen as a cure-all treatment for diseases, including the plague, measles, and smallpox. The use of the name “blessed” likely comes from its reputation as a medicinal panacea. A nearly endless list of its medicinal properties includes astringent, diuretic, antibiotic, and expectorant. It was also used for increasing blood circulation, relieving pain, and treating wounds or skin conditions. The aboveground parts of the plant were typically sourced for medicine, but the roots can also apparently be boiled and eaten. Matthiolus, a sixteenth century doctor and naturalist, purportedly wrote “there is hardly a better medication for cancer and other rotting damage” when referring to the blessed thistle…however this does lacks a reliable source. Shakespeare also made a mention of blessed thistle in his comedy Much Ado About Nothing, where it’s recommended as a herbal remedy. The Met Museum has an excellent page that dives into the medieval history of this plant. Its use as a remedy persists in modern times as a tea or tincture.