Amaranthus hybridus L.

Global description

Amaranthus hybridus is a large, erect, annual herb, reaching up to 2-3 m, reddish, frequently tinged throughout. The stems are longitudinally grooved or ridged, and usually slightly hairy. The leaves are simple and alternate, with a grooved petiole. They are ovate or elliptic-ovate, smooth or slightly undulate along the margin, and pubescent or hairless. The lower side of each leaf has elevated pinnate veins. The petioles are quite long, causing the leaves to droop downward somewhat. The inflorescences are elongated panicle of spikes or simple spikes with small reddish flowers. They are borne at the tip of the stem and in the axils of the leaves. The individual spikes have a bristly appearance because of the linear bracts surrounding the flowers. Small male (staminate) and female (pistillate) flowers are found on the same plant. Each flower has five pink sepals and no petals. The fruit is a one-seeded bladder-like membrane (utricle) that splits apart to release the seed. The small seeds, produced in abundance, are flattened, dark brown or black, circular, and shiny.

Cotyledons

Cotyledons 5-8 x 1.5-2 mm, long and slender petioles or the cotyledon base very attenuated in petiole.

First leaves

First pair of true leaves +/- ovate, apex retuse and apiculate, base cuneate or attenuate. At the tenth leaf stage: leaves +/- ovate, apex obtuse, slightly emarginate and aristate, base attenuate. Petioles long and slender. Stem clothed in tortuous pale coloured hairs.

General habit

Herb 1-2 (-3) m tall

Underground system

Taproot, short and stout.

Stem

Stems often tinged reddish, erect, occasionally ascending, branched, striate, glabrous to moderately pubescent with multicellular hairs.

Leaf

Leaves lanceolate to ovate or rhomboid, blades 3-19 (-30) cm long, 1.5-8 (-12) cm wide, apex acute to obtuse, with mucronate, base cuneate to broadly cuneate, margin entire; lower surface glabrous or sparsely pilose along the margin and veins; lateral veins often pink or red, looping inside the blade margin; petioles 0.5-15 cm long, grooved on the upper surface.

Inflorescence

Flowers in yellowish, green, reddish or purple axillary and terminal spikes formed of cymose clusters, which are increasingly closely approximate upwards, the terminal inflorescence varying from a single spike to a broad much-branched panicle up to more or less 45 x 25 cm, the ultimate spike not infrequently nodding; male and female flowers intermixed throughout the spikes.

Flower

Flowers yellowish green, reddish, or purple. Each flower subtended by a bract which is longer than the flower. Tepals rather papery, tapering to a fine point at the apex. Male flowers: Flowers about 2 mm long, tepals about 1-1.5 mm long. Anthers about 0.8 mm long. Female flowers: Flowers about 2 mm long. Ovary, styles and stigma about 2 mm long. Ovary laterally compressed, the 'equator' marked by a line. Stigmas three, clothed in glandular hairs.

Fruit

Utricles obovoid or elongate-ovoid, 1.5-2.5 mm, shorter than tepals, smooth proximally, lid verrucose or rugose, dehiscence regularly circumscissile, or rarely in some presumably hybrid forms, irregularly dehiscent or indehiscent.

Seed

Seeds black to dark reddish brown, lenticular to lenticular-globose, 1-1.3 mm, smooth, shiny, faintly reticulate around the margin. Embryo U-shaped, just inside the testa and surrounding or enclosing the endosperm.

Origin

Amaranthus hybridus is native to America.

https://www.gbif.org/species/5384364