Erigeron bonariensis L.

Global description

Erigeron bonariensis is an annual herbaceous plant growing first in rosette and then with erect stem bristling with stiff whitish hairs, rather branched upwards. The simple leaves are arranged alternately along the stem. The bottom ones are narrow and elongated, irregularly toothed. The top ones are linear, short and entire. The limb is covered with hairs on both sides. The flowers are gathered in small, whitish capitules, grouped in panicules at the end of the twigs and stem. The inflorescence that completes the axis is often overtaken by the underlying twigs, hence an inverted pyramid inflorescence with a flat or hollow top. The fruit is small, bristling at the top of many whitish silks.

Cotyledons

The cotyledons are oval-shaped attenuated and rounded apex, they are located at ground level.

First leaves

The first leaves are arranged in rosette at the beginning, they gradually separate from each other as the stem lengthens. They are linear to lanceolate in form, attenuated at the base and acute at apex.

General habit

Annual herbaceous plant raised 20 to 95 cm high, sometimes up to 2 m, greyish in color due to the short pubescence that completely covers it.

Underground system

Main root is a taproot.

Stem

The stem is cylindrical, straight, streaked, fluted, pubescent with rough hair. It is slightly lignified at the base and breaks easily. Isolated plants are branched from the base. In dense populations, only the upper part of the stem is branched. The twigs are straight and erect, very leafy. They go beyond the top of the main axis, hence an often characteristic appearance from the top of an inverted pyramid plant.

Leaf

The leaves are simple, alternate, sessile. They are narrow and elongated, attenuated at the base and acute at apex. The lower leaves are linear lanceolated, margin with some large teeth. They are 7 to 15 cm long and 1 to 3 cm wide. Towards the top of the stem, they become linear with entire margin with simply the central rib marked, then gradually reduce to linear bracts. All leaves are covered with a shaved pubescence on both sides.

Inflorescence

Inlorescence is a set of clustered panicules at the end of the twigs and stem. The terminal panicule of the main stem is shorter than the lower twig panicules, giving a general inverted pyramid appearance characteristic of this species. These panicules carry isolated pedunculate capitules. The capitules are carried by a pedicelle 1 to 3 cm long. They are ovoid or campanulated in shape, 6 to 7 mm long and 8 to 10 mm in diameter. The involucre is covered with narrow, pubescent, very acute bracts. The capitules are very broadened at maturity.

Flower

Many (about 250) peripheral female florets ligulate filiform on several rows (very small ligule, 0.5 mm), of whitish color. Central florets hermaphrodites, yellowish tubular corolla terminated by 5 pointed lobes.

Fruit

Achene finely pubescent 1 mm long, obconic compressed with 4 longitudinal ribs, topped by a 1 mm whitish to yellowish silk pappus.

Origin

Erigeron bonariensis is native to South America

Worldwide distribution

This species has been introduced to Europe and Africa. It is now widely distributed on all continents in both temperate and tropical regions.

https://www.gbif.org/species/3146717