Bitterweed

Images

Click on image to view full size

Bitterweed habit

Bitterweed

Bitterweed

Bitterweed

Bitterweed leaves

Bitterwed

Bitterweed habit

Bitterweed

Bitterweed florets

Bitterweed flowers

Morphology

Stem

Erect, leafy, bushy-branched, grooved, lightly pubescent to nearly glabrous, aromatic.

Leaves

Alternate,; basal rosette leaves wither and drop early; stem leaves numerous, nearly sessile, simple, .8 to 4 inches long, pinnately-divided to midrib, lightly pubescent to nearly glabrous; segments 3-15, thread-like, minutely resin-dotted; foliage aromatic when crushed.

Inflorescence

Heads, numerous, solitary on terminal or axillary stalks; stalks 1 to 6 inches long.

Flower

Involucre bell-shaped; bracts in 2 dissimiliar series; outer bracts 8-13, rigid, lanceolate, thickened, united at base, tips pointed; inner bracts distinct to base, leathery, slightly longer than outer bracts; ray florets 6-13, 2/5 to 3/5 inch long, yellow, turned downward at maturity; tips widened, 3-lobed; disk florets fertile, orange.

Fruit

Achene, top-shaped, to 1/12 inch long, weakly 4-angled, coarsely hairy, tipped with 5-6 translucent, pointed scales, enclosing small seed.

Ecology

Habitat

Open disturbed areas, roadsides, heavily grazed pastures, lake beds; limestone soils.

Distribution

Principally southwest 1/4 of Kansas.

Reproduction

From seed.

Practical Information

Toxicity

Poisonous to livestock. Sheep and goats in poor condition are particularly susceptible. Bitterweed is generally unpalatable but is often ingested in the winter or early spring when other forage is unavailable. It is most toxic near the time of flowering and the toxic effects are cumulative. Clinical signs include depression, decreased appetite, weight loss, and walking with difficulty. Bitterweed is said to have contributed to the decline of sheep production in the Southwest.

Additional Notes