Kansas Wildflowers and Grasses

WESTERN RAGWEED

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Ambrosia psilostachya DC.

Konza Prairie, Riley County, Kansas

Perennial

Height: 4-24+ inches

Family: Asteraceae - Sunflower Family

Flowering Period: April, May

Stems:

Erect, branched above.

Leaves:

Opposite below, alternate above; petiole 0 to 1.2 inch; blade deltate to lanceolate in outline, .8 to 5.6 inches long, .4 to 2 inches wide, pinnately toothed to 1-pinnately lobed, base wedge-shaped to truncate, ultimate margins entire or toothed, surfaces hirsute to strigose.

Inflorescences:

Heads discoid, unisexual, pistillate below staminate, staminate usually in raceme-like to spike-like arrays.

Flowers:

Pistillate heads: phyllaries 12-30(-80) in 1-8 series, outer ones distinct or connate, inner ones connate, eventually forming hard bur with free tips becoming tubercles or spines; floret 1; corolla absent. Staminate heads: peduncle short; involucres cup-shaped to saucer-shaped, 1/12 to 1/5 inch wide, minutely hairy; phyllaries 5-16 in 1 series, connate; receptacles flat to convex, chaff bracts spatulate to linear; florets 5-15(-30); corolla white to purple, funnelform, lobes 5.

Fruits:

Achenes ovoid to fusiform, enclosed in bur; burs nearly pyramidal to globose, 1/12 to 1/8 inch, minutely hairy, spines or tubercles 0 or 1-6, mostly distal, tip straight; pappus absent.

Habitat:

Tallgrass, mixed-grass, shortgrass, sand, and sandsage prairies, pastures, roadsides, disturbed sites

Distribution:

Occurs statewide

Origin:

Native

Uses:

Pueblo women drank a tea made from the plant in cases of difficult labor at childbirth, the Kiowa applied a decoction as a wash for sores on humans or on horses, and the Cheyenne drank a tea of ground leaves and stems to treat colds, bowel cramps, bloody stools, and constipation.

Comments:

The pollen is a major cause of allergy symptoms in the late summer and early fall. Ambrosia "food of the gods," allusion unclear and psilostachya, naked + spike.

Western ragweed leaf