The Snow Ghost of the Screes

Habit: A robust perennial herb 20-50 cm tall. Stems: Thick, short and covered with a dense white-tomentose indumentum that gives the plant its snowy appearance. Leaves: Lanceolate and deeply pinnatipartite, divided almost to two-thirds into 9-10 triangular segments on each side. Each segment ends in a sharply pointed golden spine, 5-9 mm long. The leaf surface is bicoloured: grey-cobwebby above and white-tomentose beneath. Flowers: Arranged in few capitula, from 1 to 5, forming a loose corymb at the stem apex. All florets tubular, hermaphrodite and deep purple, 30-35 mm long. Involucre hemispheric and floccose, made of imbricate lanceolate scales ending in long spines; the outer scales are typically reflexed downward. The receptacle is covered with characteristic bristle-like chaff. Fruits: An obovoid cypsela, 4.5-5.5 mm long, soft in texture and dark brown-black with mottling. Flowering: May-July.

Chorological type: Italian endemic. Distribution: Present only in Basilicata, Calabria and Sicily. Habitat: It grows mainly in stony places, extremely dry calcareous screes and debris slopes, between 1200 and 1900 m above sea level.

Generic name (Ptilostemon): Composed of the Greek words ptilon, “feather”, and stemon, “thread” or “stamen”. The name refers to the structure of the pappus, the feathery appendage of the fruit that aids wind dispersal. Specific name (niveus): From the Latin niveus, derived from nix, “snow”, meaning “snow-white”. The epithet perfectly describes the dense white woolly indumentum covering the stem and the underside of the leaves.

Snowy thistle represents a species of great phytogeographical interest because of its restricted range. As a narrow endemic, conservation of its habitat, often threatened by overgrazing or excessive trampling, is essential for the survival of the species.