Bitterweed (Bitter Sneezeweed)

Helenium amarum

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Photo of blooming bitterweed plant shown from top.
Bitterweed is the weediest sneezeweed in Missouri. Its home range is in Texas and Louisiana.
Theodore Webster, USDA Agricultural Research Service, Bugwood.org
Other Common Name
Yellow Dog-Fennel
Family

Asteraceae (daisies, sunflowers)

Description

Much-branched annual. Flowerheads few to many on naked stems above the foliage, yellow, the 5–10 ray florets reflexed and notched; the disk bowl-shaped, pointing skyward, yellow. Blooms June–October. Leaves profuse, linear (very narrow), to 1½ inches long with smaller leaves arising from axils of larger ones. Plant contains bitter, toxic substances, and cattle forced to graze on it in overgrazed pastures produce bitter milk, thus the name bitterweed.

Similar species: Four species of Helenium grow in Missouri. The others are discussed elsewhere in this guide. All have rounded disks and yellow, fan-shaped, drooping ray flowers. This is the only one that is annual, has profuse, linear leaves, and lacks wings of leafy tissue on the stems.

Size

Height: usually to 1 foot, but rarely to 2 feet.

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Photo of bitterweed plant, side view, showing very narrow leaves and branching.
Bitterweed (Bitter Sneezeweed; Yellow Dog-Fennel)
Bitterweed has very narrow leaves, and it forms many branches at the top part of the plant.

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Photo of field dominated by blooming bitterweed, with cattle trying to graze it.
Bitterweed (Bitter Sneezeweed; Yellow Dog-Fennel)
Toxic chemicals in bitterweed cause cattle to avoid eating it. Instead, they eat nearly any other plant within reach.

bitterweed_young_basal_leaves_9-22-14.jpg

Photo of young bitterweed plant, showing basal whorl of dandelion-like leaves.
Bitterweed (Bitter Sneezeweed; Yellow Dog-Fennel)
The basal leaves of bitterweed resemble dandelion leaves. They wither away before flowering time.

bitterweed_flowerheads_9-22-14.jpg

Photo of bitterweed flowerheads.
Bitterweed (Bitter Sneezeweed; Yellow Dog-Fennel)
Bitterweed has 5–10 fan-shaped ray flowers and narrowly linear leaves.
Habitat and conservation

Occurs on banks of streams and rivers, openings of dry upland forests, and disturbed portions of upland prairies; also pastures, farmyards, railroads, roadsides, and open, disturbed areas. It forms dense populations along mowed roadsides and in overgrazed pastures. The weediest sneezeweed in Missouri, bitterweed’s home range is in Texas and Louisiana. It was first collected in our state in about 1879, and over the next 20 years it increased its range rapidly.

image of Bitterweed Bitter Sneezeweed Yellow Dog Fennel Distribution Map
Distribution in Missouri

Scattered to common, mostly south of the Missouri River.

Human connections

The dried and powdered flowers were historically used as snuff. Sneezeweeds contain toxic, bitter substances. In the West, they cause “spewing disease” in cattle, with vomiting, diarrhea, and death. Grazing animals avoid these plants. Pastures full of sneezeweeds have probably been overgrazed.

Ecosystem connections

Bees, wasps, butterflies, beetles, and other insects collect nectar and pollen from the flowers. The larvae of some moths bore into the stems and roots, and weevil larvae bore into the immature seeds. Prairie-chicken are known to eat the seedheads. Most mammals avoid eating the bitter foliage.