Sonchus asper (L.) Hill.

Global description

Sonchus Asper is an erect herbaceous plant, thorny aspect, glabrous. The stem is hollow and wide. It exudes a white latex when injured. The leaves are quite stiff, spiny appearance, and slightly prickly. They are alternately arranged along the stem. In the upper part of the plant, the leaf base is expanded in a wide rounded ear masking the stem. The flowers are assembled into yellow heads grouped side by side on the widened part of the shaft which carries the inflorescence. The fruit is smooth. It carries at its top a tuft of many cottony white hairs. It does not open at maturity.
 
Cotyledons

Oval cotyledons, of reduced size, 4 to 6 mm long and 3-4 mm wide. They are shortly stalked (1 to 1.5 mm). The lower face is sometimes purple.
 
First leaves

First leaves are simple, arranged in a rosette, and then alternate. The first leaf has an elliptical blade, more or less rounded, provided with some spinous discrete tines. The second leaf is an elongated elliptical blade. It is more clearly serrated and thorny. The following leaves are lance-shaped to obovate with lamina attenuated   more or less rapidly in a foliaceous petiole, of variable size and partially serrated. The leaves are covered with a whitish fluff of multicellular hairs, and articles arranged in strings. The underside is sometimes tinged with pale red.
 
General habit

Annual or biennial plant reaching 30-150 cm in height.
 
Underground system

The root is a short taproot with fibrous side roots.
 
Stem

Erect, angular and weakly ridged, hollow, Stem branched or unbranched, exuding a white latex when cut.
 
Leaf

Leaves simple, alternate, lanceolate, and quite stiff. They are sessile, the base of the blade is attenuated and then expanded around the stem by two large atria, clasping, rounded to sharply serrated and thorny margin. The blade is 10 to 30 cm long and 2 to 8 cm wide, more or less lobed. The apex is wedged The margin is wavy and irregularly serrated, often tinged with purple.
 
Inflorescence

Terminal inflorescence, formed of a group of shortly stalked capitulums. The capitulums, yellow in colour, are flat and measure 2 to 3 cm in diameter at the blossoming. The involucre of bracts are arranged in 2 or 3 rows. The outer bracts are lanceolate, 3 mm long. The inner bracts are linear, lanceolate, 10 mm long. The base of the capitulum often has a woolly pubescence, deciduous.
 
Flower

The florets are all ligulate, hermaphrodites. The corolla tube is 5 mm long, with few hairs at the top, and ends with a ligule of 5 small tines.
 
Fruit

The fruit is a flattened achene, oval elliptical, smooth, brown, 2 to 3 mm long, marked with 3 longitudinal protruding ribs. The top of the achene is topped by a pappus of numerous denticulate white bristles, 8 to 10 mm long.

Origin

Sonchus asper is native to Europe, northern Asia and the northern half of Africa.

Worldwide distribution

This species is widespread in Europe, Africa, Asia, and has been introduced into America, Southern Africa, the Indian Ocean, India and South East Asia and Australia, New Zealand.

https://www.gbif.org/fr/species/3105782