This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Names: False Sunflower, Swamp Sunflower, Yellow Ox-eye, Staggerweed.
This native plant is found in moist places throughout the country, and contains poison in all its parts, but more particularly in the flowers. In powdered form the plant is used to some extent in medicine, producing violent sneezing when inhaled.
The flavour is bitter, and animals usually leave it alone. Chesnut states, however, that it often poisons cattle, horses and sheep that have been lately moved to places where it is plentiful. It is claimed that a taste for the plant is developed, inducing the animal to eat an amount sufficient to produce death. Horses and mules are more susceptible than other animals.
"The symptoms, as determined by experiments made in Mississippi upon calves, are an accelerated pulse, difficult breathing, staggering, and extreme sensitiveness to the touch. In fatal cases, death is preceded by spasms and convulsions." (Chesnut).
Melted lard is a most effective remedy, and relieves the symptoms in so short a time that investigators have been led to believe that its action is merely that of an emollient, relieving the burning in the alimentary canal. When this relief is obtained the nervous symptoms cease at once.
The plant is an erect branching perennial, somewhat downy, and from two to six feet high. Each of its numerous flower heads, an inch or more broad, consists of a globular mass of yellow disc florets, surrounded by a row of fertile yellow rays. The leaves are lanceolate, sessile, rather thick, and usually toothed.