Kingdom Plantae
Sub Kingdom Tracheobionta (vascular plant)
Superdivision Spermatophyta (seed plant)
Division Magnoliophyta (flowering plant)
Class Magnoliopsida (dicotyledon)
Order Caryophyllales
Family Amaranthaceae
Genus Amaranthus
Species retroflexus
Classification L.
Common Name common amaranth, red-root pig weed

Geographic Range original from Central America: it can be found in North America, South America, Europe, Eurasia, Africa.
Physical Characteristics annual dicotyledonous plant, infesting. It can reach 120 centimeters in height. The stem that is found below the cotyledons is glabrous, even if a thin duvet can sometimes cover it and it can be reddish near the basis. The cotyledons are narrow, from 10 to 12 metres long, and have a colour which ranges from green to reddish on the upper side. The first leaves are alternate, oval, and slightly dentate on the apex; the following leaves are alternate. There can be some filaments on the borders of the leaves and along the veins, most of all on the surface of the lowest leaves. The leaves are alternate, form 8 to 10 centimeters long, ovate, with waving borders; the petiole is about 1 centimeters long. The stem is strong, straight and branched and can reach 120 centimeters in height. It sometimes has hairs, especially near the upper part of the plant. It has a taproot, often reddish. The flowers are small and green; they are produced in thick and compact terminal panicles, up to 16 centimeters long. Small inflorescences can be found also between the stem and the petiole of the leaves. Male flowers and the female ones are on the same plant. Each terminal panicle contains a lot of spikes, thickly packed, that have 4 –8 millimeters long bracts.
Notes it produces a lot of seeds that can remain vital even for 5 years. It blooms from May to September.
Habitat cultivated fields, pastures, ditches along roads, deserted areas.

References Department of Plant Pathology, Physiology & Weed Science - Virginia Tech University
ARPA Veneto
Web References http://www.ppws.vt.edu/
Source of the photo http://www.nwr.mcnary.wa.us/plant18.html (1)

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