Amaranthus retroflexus

Basic information
Scientific name	Amaranthus retroflexus	Click to magnify
Common names	Redroot pigweed, Carelessweed, Redroot Amaranth
Higher taxon	Amaranthaceae, Caryophyllales, Magnoliopsida, Magnoliophyta
Natural range	North America.
Habitat	Crop field, some kind of farm area, grassland, urban area, vacancy.

Invasion information
Range in Japan	Almost entire Japan
Origin	Unknown.
Date	Around 1890.
Route	Accidental: Unknown vector.
Impact	Competition. Allolopathy. Host for insects, nematodes, fungi, viruses, and parasitic plants. Allergen for hay fever. Accumulation of nitrate salt (harmful to husbandry). Native organism(s) affected: Native, crop, pasture plants, etc.
Regulation in Japan	No action for prevention, mitigation, control, or eradication.
Introduced range in other countries	South America, Europe, Asia, Africa, Oceania.

Reference	Notes
Jpn Assoc Advanc Phyto-Regul & Inst Contr Agrochem, Minist Agr, China (2000) Chinese Colored Weed Illustrated Book. Zenkoku-Noson-Kyoiku-Kyokai, Tokyo Satake et al. (1982) Wild Flowers of Japan, Herbaceous Plants [II]. Heibonsha, Tokyo (in Jpn) Shimizu (ed) (2003) Naturalized Plants of Japan. Heibonsha, Tokyo (in Jpn) etc.	Excluded by competition with other congeneric invasive weeds such as Amaranthus hybridus and A. palmeri