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Amaranthus retroflexus

Basic information
Scientific name Amaranthus retroflexus

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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 Range in Japan
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).
Affected organism: 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