Noxious Weed - Catsear

Catsear, or Hypochaeris radicata, is a noxious weed found in many horse pastures. The plant is native to Europe, but has been introduced to the Americas, Japan, Australia and New Zealand. Also known as false dandelion, catsear is commonly mistaken for true dandelions as both plants carry similar flowers which form windborne seeds. These plants also have a rosette of leaves and a central taproot. Key distinctions can be made however when comparing the stems and leaves of catsear and dandelion.

Catsear flowering stems are forked and solid with multiple flowers per plant, whereas dandelions possess unforked stems that are hollow with a single flower. The leaves of catsear are dark green, lobe-shaped and hairy which is in stark contrast to dandelions, which have jagged, hairless leaves that are a lighter shade of green. Catsear and dandelions are typically found at different times of the year as well. Catsear is more commonly seen in early summer, with dandelions more prominent during early spring. Mild, humid conditions are known to promote growth for both plant species. This was a concern for horse owners in 2012, when there was an increased presence of catsear in horse pastures in the Northeast due to humid conditions.

Catsear is typically not harmful unless consumed in large quantities. However, it is suspected of causing stringhalt in horses if consumed in excess. Stringhalt is a neurologic issue characterized by a sudden, exaggerated flexion of one or both hind legs of the horse. It is most easily seen while the horse is walking, trotting, backing up slowly, turning on the affected leg, or suddenly frightened or excited. When a horse has stringhalt due to catsear consumption, it is referred to as Australian stringhalt, due to the prevalence of catsear in Australia. Stringhalt has been associated with poisoning from vetch and sweet pea plants as well. If you suspect your horse is having health-related issues from consuming high quantities of catsear, remove your horse from the area containing the plant and contact your veterinarian immediately.

Horse owners must be vigilant in caring for their pastures and managing catsear presence to reduce risk. Unlike many other weeds, horses may eat catsear even if other quality forage is available. It is recommended that catsear be removed, by either digging up the plant (including roots) or applying an herbicide. Contact your local county Extension office to determine which herbicide to use and the appropriate application amount. Follow directions found on the herbicide label carefully and ensure that horses are kept off of the treated area as directed.

If you need assistance identifying and managing catsear, please reach out to your local county Extension office.

For More Information

Yellow Flowers in the Pasture Safe or Dangerous - Rutgers University

Common catsear (Hypochaeris radicata) - University of California Integrated Pest Management program

Hypochaeris radicata - North Carolina State University Extension