By Mindy Hittle-McNair, Walton County Extension Agent
There is a problematic winter annual found on bare-ground, along tree lines, and under fences. Urtica chamaedryoides commonly called fireweed, heartleaf nettle, weak nettle, or ortiguilla is a native Florida species.
This plant’s range extends from south Florida to southern Ohio, Kentucky, southern Illinois, to southeastern Kansas, Texas, Louisiana, and Mexico. The Florida’s Urtica species is troublesome because of the stinging hairs which contain irritants.
Humans and animals will have a wide range of reactions to this plant. The hairs on the plant inject irritants that are very painful. Cattle generally avoid this plant but, but horses have been know to accidentally browse or roll in the plant causing minor to extreme irritation.
Controlling this plant is a challenge. Mowing appears to provide no control of this species. At this time herbicides are the best way to treat pastures. GrazonNext, Remedy, or Pasturegard provide the best control of this weed and are safe to use in pastures. Using these specific chemicals on this weed can take up to two weeks for the weeds to turn yellow and die.
Timeliness is critical for managing this pasture weed. Urtica species start to die off and disappear with the onset of warmer temperatures and the summer season, so spray early to prevent further seed production. A quart of Remedy and GrazonNext per acre and 1.5 quarts of Pasturegard are recommended to control this weed.
For more information, download the UF/IFAS Fact Sheet on fireweed: http://edis.ifas.ufl.edu/pdffiles/AG/AG25200.pdf