Kansas Wildflowers and Grasses

BITTERWEED

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Hymenoxys odorata DC.

Morton County, Kansas

Annual

Height: 3-20 inches

Family: Asteraceae - Sunflower Family

Flowering Period: May, June, July, August

Stems:

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.

Inflorescences:

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

Flowers:

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.

Fruits:

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

Habitat:

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

Distribution:

Principally southwest 1/4 of Kansas.

Reproduction:

From seed.

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.

Comments:

From Greek hymeno "membrane" and oxys "sharp" alluding to the pointed pappus scales. Bitterweed does not compete well with grasses. It will flourish on deteriorated rangeland.

Bitterweed