Centaurium erythraea

Morphological description

Biennial or annual herbaceous plant, with an erect habit and variable height between 10 and 60 cm. The stem is generally simple, rarely branched at the base or in the middle, while branching is more frequent in the upper part; it is glabrous, quadrangular in section with about 6 prominent sub-winged ribs. The root system is taproot, deep.

The basal leaves form a persistent rosette, are sessile with an oblanceolate, elliptical or obovate blade, on average 3-5 cm long and 1-1.5 cm wide, with entire margin and 3-7 well-marked parallel veins. The cauline leaves are opposite, sessile, narrower and lanceolate or oblanceolate, smaller than the basal ones and often more lanceolate or linear.

The inflorescence is terminal, corymbose or corymb-umbellate, often leafy with bifurcate cymes. The flowers are pentamerous, rarely tetramerous, with a funnel-shaped corolla of pink color, which can vary from pale pink to intense pink, rarely white. The corolla is formed by five oval petals with pointed apex, 5-6 mm long, generally shorter than the corolla tube, which measures between 6 and 10 mm. The calyx is 4-6 mm long, with five strap-shaped, linear and acuminate lobes, about half or three quarters the length of the corolla tube, with five prominent angles and evident ribs.

The stamens are five, with yellow anthers about 1.5 mm long that curl spirally after dehiscence. The style is single, with a strongly bilobed and deciduous stigma. The fruit is a cylindrical or fusiform capsule, about 10 mm long, with a thin and papery wall, composed of two locules containing numerous small, globose seeds, brown in color with a reticulated and papillose surface.

The whole plant has a very bitter taste, due to the presence of bitter compounds such as the glucoside eritaurin, gentiopicrin and other active principles typical of Gentianaceae.

Habitat and distribution

Thermophilic species, widespread throughout the Italian territory from the plains up to the high hills, generally up to 1500 m altitude. It prefers sunny or slightly shaded environments, frequently growing in forest clearings, glades, dry meadows, path edges and sandy or well-drained soils.

It is common in Mediterranean regions and much of temperate Eurasia, with presence also in North Africa. In Italy, besides the peninsula, it is widespread in the major islands, particularly Sardinia and Sicily, which represent a center of genetic variability for the species.

Flowering period

Flowering mainly occurs from May to September, with possible variations related to altitude and latitude. In general, in warmer climates and Mediterranean areas flowering can start as early as May, while in cooler areas it extends until September.

Ecology and pollination

The species is mainly pollinated by pollinating insects that visit the flowers for nectar and pollen, attracted by the bright pink color and the funnel shape of the corolla. The flowers open only during daylight hours and close by noon or in case of cloud cover, a behavior that regulates pollination in relation to environmental conditions.

Seed dispersal occurs through falling from the capsule, which opens releasing the small papillose seeds, favoring limited short-distance propagation, but the species is also able to expand thanks to its genetic variability and adaptability to different habitats.

Curiosities and traditional uses

The common name “centaurea maggiore” recalls the popular tradition linked to the mythological figure of the centaur Chiron, who was said to have discovered the therapeutic virtues of the plant. Historically, the plant was known as “fel terrae” (bile of the earth) for its intense bitter taste.

The plant has long been used as a popular and medicinal remedy, especially for its digestive, stomachic, tonic, carminative and febrifuge properties. In the past, it was used as a substitute for quinine in the fight against malaria, particularly in Southern Italy. The leaves and flowering tops are collected and dried to prepare decoctions, infusions and mother tinctures.

Some traditional uses include the use of crushed green leaves to disinfect wounds and as a healing agent, as well as being used as a post-shampoo treatment for hair care. However, an overdose can cause gastrointestinal irritation, vomiting and diarrhea.

During the Middle Ages, the plant was widely cultivated in abbey gardens and by the Gauls for its therapeutic virtues. Today it is also used in the preparation of vermouth, a liqueur with eupeptic effects on gastric secretion.

Etymology

The genus name “Centaurium” derives from John Hill and refers to the small “Centaurea minor” cited by Bauhin, recalling the mythological figure of the centaur Chiron, who according to legend used this plant for its medicinal properties.

The specific name “erythraea” derives from the Greek “erythros”, meaning “red”, alluding to the color of the flowers, which vary from bright pink to pale pink. The Italian common name “centaurea maggiore” reflects popular tradition and the resemblance to other species of the genus Centaurea, although it belongs to a different family (Gentianaceae).

Sources

• Prof. S. Pignatti, "Flora d'Italia"
• Acta Plantarum - Flora delle regioni italiane (sheet by Nino Messina)
• Tela Botanica / H. Coste, "Flore descriptive et illustrée de la France"
• World Flora Online (WFO)