Giant ragweed

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Giant ragweed

Giant ragweed inflorescence

Giant ragweed leaves

Giant ragweed

Giant ragweed

Giant ragweed

Giant ragweed staminate inflorescence

Giant ragweed

Giant ragweed

Giant ragweed inflorescences

Giant ragweed inflorescence

Morphology

Stem

Erect, usually simple or sparingly branched above, longitudinal ridges, rough, short-hairy.

Leaves

Mostly opposite, uppermost often alternate, simple, rough; stalks .4 to 2.8 inches long; blades of lower and middle leaves egg-shaped to nearly circular in outline, 4 to 8 inches long, 1.2 to 7.8 inches wide, usually palmately 3- to 5-cleft; margins usually toothed; upper surface somewhat spreading-hairy; lower surface nearly smooth; upper leaves smaller, 3-cleft to nearly entire.

Inflorescence

Monoecious (staminate and pistillate heads occur at different locations on same plant); heads of staminate florets in racemes, elongated, to 6 inches long, panicle-like, terminal; heads of pistillate florets in clusters in axils of bracts below staminate inflorescences.

Flower

Greenish-yellow; staminate heads short-stalked, saucer-shaped, 1/12 to 1/6 inch across, 6-8-lobed; florets 3-25+; pistillate heads with egg-shaped involucre, about 1/6 inch long, 1-flowered.

Fruit

Bur-like, pyramidal, 1/5 to 1/3 inch long, hard, formed by floral bracts, glabrous or sparsely-hairy; beak 1/25 inch long, surrounded by 4-8 blunt spine-like projections; seed 1, small.

Ecology

Habitat

Moist disturbed sites, stream banks, roadside ditches, margins of ponds and lakes, old fields, waste areas, pastures.

Distribution

Throughout Kansas

Reproduction

By seeds

Practical Information

Forage Value

Unpalatable for livestock, though horses will sometimes eat it. Deer eat the leaves and pheasants, quail, prairie chickens, and songbirds eat the fruits.

Uses

Native Americans rubbed crushed leaves on insect bites and steeped the leaves to make a tea taken for fevers and pneumonia and used as a wash for hives. The root was chewed to alleviate fear at night. Stem fibers were used as thread. Giant ragweed provides wildlife cover.

Additional Notes