Helenium autumnale L.—Sneezeweed
FAMILY: Compositae (Asteraceae)—the Daisy Family (see Arctium)
PHENOLOGY: Helenium species flower late in the growing season, from August through October.
DISTRIBUTION: Sneezeweed is an inhabitant of moist low ground, rich thickets, meadows, and shores.
PLANT CHARACTERISTICS: The fibrous-rooted perennial H. autumnale grows to 1.5 m tall. The stems bear wings originating as decurrent leaf leaves: numerous, lance-linear to elliptic, almost sessile; lower leaves deciduous; heads: several or many in a leafy corymbosely branched inflorescence, or simple; disks: yellow, 8-20 mm wide; rays: toothed or lobed, 10-20, pistillate or sometimes neutral, 1.5-2.5cm long and 7-12 mm broad; pappus: keeled scales, brown, ovate, tapering into a short awn.
POISONOUS PARTS: All parts of the sneezeweed plant, especially flowers, are toxic. Experiments show 1% (dry) of a sheep's weight of Helenium will cause illness and death within 8 days.
SYMPTOMS: Early signs of Helenium poisoning are dullness and depression; weakness, tremors, and rapid respiration and pulse ensue. Nausea and vomiting may be present. Other symptoms include excessive salivation, belching, frothing, and intestinal disorders. Animals not displaying vomition will often recover. The prognosis for those vomiting is less positive.
Postmortem: gross and histological lesions: Examination reveals gastrointestinal degeneration and liver, kidney, and lung damage; hydrothorax, ascites, congestion, and edema in the forestomachs (submucosa of the rumen and reticulum); edema of nervous tissue; and sometimes mild tubular nephrosis, as well as fatty changes in the myocardium.
POISONOUS PRINCIPLES: The toxin in some species is a glycoside, dugaldin, whereas in other taxa it is the sesquiterpene lactone helenatin
CONFUSED TAXA: The combination of yellow ray and disk flowers, scaly-awned pappus, alternate leaves, and truncate style-branches without appendages are unique to Helenium. The closely related genus Gaillardia is similar except the style-branches have subulate appendages.
SPECIES OF ANIMALS AFFECTED: Sheep are apparently very sensitive to sneezeweed, but the poisonous principle will affect all livestock and humans. Sheep will eat this bitter weed when all other forage is unavailable. The toxin remains poisonous when dried; therefore, contaminated hay is also undesirable
TREATMENT: (11a)(11b); (26)
OF INTEREST: In addition to H. autumnale, several less common, introduced taxa are found in Pennsylvania: H. amarum (Raf.) H Rock, H. flexuosum Raf., and H. quadridentatum Labill.