Sigesbeckia orientalis L.

Global description

Sigesbeckia orientalis is an erect branched herb, 20 to 60 cm high. The leaves are grayish green, slightly viscous. They are inserted in pairs on either side of the stem. They are roughly cut in tines on the edge. The lamina has characteristics purple veins, very clear. The flowers are yellow. They are held in small spherical sticky heads at the top of the plant. They are supported by small spatulas shaped hairy and sticky leaves.
 
Cotyledons

Cotyledons short stalked. 10 mm long and 5 mm wide. The lamina is rounded oval, attenuated at the base, fleshy, glabrous.
 
First leaves

Leaves simple, opposite, decussate, velvety of grayish-green in color. They are stalked. The lamina is entire with wide angled or truncated at the base, slightly decurrent along the petiole and acute at the apex. The margin is entire to slightly serrated. Purple ribs clearly visible.
 
General habit

Erect, branched herbaceous plant, 30-60 cm high.
 
Underground system

The root system is a branched taproot.
 
Stem

Cylindrical, solid stem. It is glandular pubescent at the top. It is dark green, often washed with purple.
 
Leaf

Leaves simple, opposite, decussate, carried by petioles, 1 to 1.5 cm long, whose bases are joined around the stem. The lamina is oval to lanceolate, with wide angle at the base and slightly decurrent along the petiole, acute or acuminate apex. It is 6 to 7 cm long, 2.5 cm wide. The margin is coarsely serrated. The upper surface is finely pubescent to glabrous. The underside is glandular pubescent, slightly viscous. The terminal leaves are oblong lanceolate, they are usually washed in purple at the base.
 
Inflorescence

The flowers are assembled in isolated  terminal capitulums or by 2 to 3 at the end of a stem of 3 cm. The capitulum is loose, surrounded by an involucre of bracts in 2 series. External series consists of 5 spatulate bracts, 7 to 8 mm long, far beyond the capitulum. They bear glandular hairs, in sticky pinheads. The internal series includes 5 obovate bracts with glandular hairs, 5 mm long, applied at the base of capitulum. This one includes 6-8 external, ligulate, florets and more numerous internal tubulate florest.
 
Flower

The florets have a yellow ligule, lobed at the top. The base of each flower is surrounded by glandular bracts. The central florets are tubulate, hermaphrodites, more numerous, yellow. The base of each floret is surrounded by a membranous bract.
 
Fruit

The fruit is an obovoid or obconical achene, angular, glabrous, without pappus, 3 to 4 mm long and   1 mm wide, dark brown or blackish. It is sometimes included in the membranous bract.

https://www.gbif.org/fr/species/3125901