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10th leaf stage. Copyright CSIRO
Scale bar 10mm. Copyright CSIRO
Cotyledon stage, epigeal germination. Copyright CSIRO
Amaranthus hybridus L.
Linnaeus, C. von (1753) Species Plantarum 2: 990. Type: Habitat in Virginia..
Amaranthus cruentus L., Systema Naturae: 1269(1759), Type: (none cited). [Given by C.Linnaeus, Sp. Pl. ed. 2 (1763) 1406 as Habitat in China.].
Usually flowers and fruits as a weedy plant about 1-2 m tall.
Leaf blades about 5-12 x 2.2-6 cm. Petioles grooved on the upper surface. Twigs and stems longitudinally grooved or ridged. Twigs, petioles and both the upper and lower leaf surfaces clothed in tortuous hairs. Lateral veins often pink or red, looping inside the blade margins.
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.
Perianth persistent, enclosing the fruit, the stigma persistent at the apex. Fruits about 1.2 x 1 mm. Seed small, about 1 x 1 x 0.5 mm, laterally compressed. Embryo U-shaped, just inside the testa and surrounding or enclosing the endosperm. Cotyledons about as wide as the radicle.
Cotyledons 5-8 x 1.5-2 mm, petioles long and slender or the cotyledon base very attenuate. 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.
Distribution and Ecology
An introduced species originally from North America, now naturalized in NEQ and southwards as far as south-eastern New South Wales. Altitudinal range from near sea level to 750 m. A weed of agricultural land and waste places but also found in disturbed areas and along roads in monsoon forest, vine thickets and some rain forests. Also occurs as a weed in Malesia.
Herb (herbaceous or woody, under 1 m tall)
Shrub (woody or herbaceous, 1-6 m tall)