NCSU Turfgrass Centre, Turffiles.NCSU.Edu
Horseweed is also known as manestail and has large leaves that resemble a horse's tail. It grows in a patch of elongated, toothed leaves with white, pink or yellow flowers that appear at the top part of the central stem. The younger leaves are shaped like eggs, but mature leaves are completely without petioles. This weed can grow as tall as 6 feet if left untreated.
Manestail is a highly resistant summer annual that is known to resist glyphosate herbicides. One plant can produce as many as 200,000 seeds, making it important to eliminate the weed before it spreads. A fall or early spring pre-emergent herbicide application can help to prevent it from establishing, as well as postemergent herbicides that are labeled for horseweed.