AMARANTHUS

Redroot Pigweed
Redroot Pigweed
Redroot Pigweed seedling
Redroot Pigweed Seedling
Redroot pigweed in potato
Redroot Pigweed in Potato

This genus includes all the pigweed. Most problematic of these in potato is redroot pigweed, also called rough pigweed (A. retroflexus). Redroot pigweed is native to the U.S. and found all across the country, but it is mainly a problem in the Great Plains. It was once used to make flour by Native Americans in the Plains. It is a summer annual broadleaf plant easily recognized by its well-developed pinkish taproot. The plant grows to about six feet. The stem is sturdy and erect with lots of branches. Leaves are alternate and simple. They are dull green, about four inches long, with hairs, and on the under surface, the veins are white. A plant can produce a lot of seed, up to 100,000 at maturity, and seeds can survive in the soil for 30 years. Besides competing for nutrients, the major problem with redroot pigweed in potato production is that it can cause havoc with harvest machinery, damaging tubers as well. Redroot pigweed is controlled by cultivation and some herbicides, such as EPTC in potato.

There are several other species that are common although less of a problem in potato. They include: common waterhemp (A. tamariscus), tumble or white pigweed (A. albus), Palmer amaranth (A. palmeri), and prostate pigweed (A. blitoides).


REFERENCES

  • Greider, R.S., D.R. MacKenzie, Z. Smilowitz, and J.D. Harrington. 1978. Potato Diseases, Insects, and Weeds: Northeastern United States. Publ. The Pennsylvania State Univ, University Park, PA.
  • Horak, M.J., D.E. Peterson, D.J. Chessman, and L.M. Wax. 1994. Pigweed Identification: A pictorial guide to the common pigweeds of the Great Plains. Publ. Kansas State Univ Coop Ext, Manhattan, KS.
  • Nissen, S.J. and D.E. Kazarian. 2000. Common Weed Seedlings of the Central High Plains. Publ. Colorado State Univ, Ft. Collins, CO.
  • Stubbendieck, J., G.Y. Friisoe, and M.R. Bolick. 1994. Weeds of Nebraska and the Great Plains. Publ. Univ Nebraska, Lincoln, NE.
  • Whitson, T.D. (ed.) 1992. Weeds of the West. Publ. Weed Sci Soc Amer, Newark, CA.