Verbena bonariensis L.

Global description

Verbena bonariensis is an annual to perennial herb that grows up to 1.5 m. The entire plant is roughly hairy. The stems are square in cross-section, and sometimes develop a slightly woody base. The leaves are opposite, sessile and simple; the blade is narrowly ovate, oblong or linear with pointed tip, the base slightly clasping the branches ; margins are serrated; the upper side is coarsely hairy while the underside is densely softly hairy. The numerous small, purple to lavender-pink, tubular flowers are arranged into branched, elongated clusters at the tip of the stems. The small fruit, when mature, splits into four brown elongated nutlets.

Cotyledons

Cotyledons are borne on a petiole, 5 mm long. The lamina is ovate, 8 mm long and 6.5 mm wide, with a tapered tip and an attenuate base; light green in colour.

First leaves

First leaves are simple, opposite, subsessile, lamina is ovate elliptical, 15-18 mm long and 10-12 mm wide, distinctly veined, margin is first entire, then after first leaves is serrated.

General habit

Erect, branched herb, growing up to 1.5 m tall, sometimes slightly woody at the base. Flowering in October to June.

Underground system

Taproot.

Stem

Stem is quadrangular, solid, stiff, erect, slightly furrowed on two opposite, scabrid on the angles. It quickly branches.

Leaf

Leaves are simple, opposite, decussate.The lamina is sessile, ovate oblong to linear, 6-22 cm long and 1-7 cm wide. The base is narrow at first, and then widens up, cordate or sub-auriculate to sub-amplexicaule, the apex is acute. The margin is regularly serrated except at the base. The upper surface is smooth, the lower surface hispid, more or less tomentose.

Inflorescence

Dense spikes, 0.5-5 cm long, arranged in corymb-like inflorescences, more or less loose. The stalks of these clusters and the small bracts below each flower are covered with short glandular hairs as well as longer stiff hairs.

Flower

The flower is subtended by a foliaceous bract, shorter than the calyx, pubescent, oblong to narrow oval, acuminate, green or purple, with a prominent midrib. The calyx is 2.5-3 mm long, fused into a quadrangular tube. It is densely pubescent with glandular hairs; the top is flat with four long teeth. The corolla lobes are fused into a cylindrical tube, less than twice the length of the calyx (3-4.5 mm), pubescent on the outside in the top part, and ending in 5 rounded spreading lobes (2.5-5 mm across). Corolla is bluish, purple or lavender pink.

Fruit

Fruits are dry, surrounded by the calyx, separating into four nutlets oblong to linear, trigonal, reddish brown, shiny, rough, reticulate.

https://www.gbif.org/fr/species/2925514