Cressleaf Groundsel, also known as butterweed, is in full flower currently in forage and unplanted fields across the state.  While this is not a new weed, prevalence has been increasing causing concern for many livestock producers. 

Cressleaf Groundsel is toxic to both cattle and horses.  Cattle are 30-40 times more susceptible to poisoning than sheep or goats.  Calves and younger cattle are more susceptible than older cattle, but it can be fatal at high enough doses to all age groups.  

Pyrrolizidine alkaloids are the principle toxin in these plants.  It is known to cause liver disease in cattle, producing symptoms such as listlessness, decreased appetite, depression, anorexia, diarrhea, and photosensitization in extreme cases.  

While toxicity decreases in some plants as they dry, that is not the case with Cressleaf Groundsel. These toxins are not decreased if the plants are dried and baled.  Ensilaging will decrease the concentration of toxin but not eliminate them.  

Producers with high concentrations of Cressleaf Groundsel may be forced to bale first cutting and throw it away so that livestock are not poisoned. Areas of sparse concentration may be baled and fed cautiously, ideally alongside hay that is free from poisonous weeds.  

Cattle may sort the weeds out.  A new bale should be fed before the only thing left in the feeder is weeds. 

In grazing situations, cattle will usually not eat poisonous plants as long as they have access to other quality forages.  Be cautious anytime drought conditions decrease forage stands.

Cressleaf groundsel reproduces only from seeds and emerges as a rosette in the fall, then bolts, flowers, and goes to seed in the spring.  Bolting stems are hairless, hollow, grooved, and can reach heights of three feet with inflorescences that have six to 12 yellow ray flowers.  

The flowers are like other species in the Aster family, with ray (outside) and disk (center) petals.  The outer ray will normally consist of 5 to 15 petals that are bright yellow, and the inner disk will be a more golden yellow in color.  

Plants will eventually produce seeds that resemble those of dandelions.  The seeds are small with a reddish to brown tint and have a feathery pappus that makes them easily carried by the wind.

Cressleaf groundsel normally does not regrow after the first cutting of hay; however, the goal should be to prevent it from becoming established in the field.  

Article by Jason Hartschuh-OSU Extension, Crawford County and Ted Wiseman-OSU Extension, Perry County.  Edited by Mark Badertscher-OSU Extension, Hardin County.