Bracken Fern is a common perennial fern that is found across the United States. Its ability to grow well is both dry and moist soils, as well as along tree lines, in wooded areas, and around buildings, make it a well-adapted species. While all parts of the fern are toxic, the rhizomes are most toxic, with horses and swine being most susceptible to the toxicity and ruminants being more tolerant. Toxicity is caused by an induced B1 deficiency, however, livestock rarely consume large quantities of bracken fern, unless forage availability is limited.