Kansas Wildflowers and Grasses

SOUTHERN RAGWEED

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Ambrosia bidentata Michx.

Cherokee County, Kansas

Annual

Height: 12-40 inches

Family: Asteraceae - Sunflower Family

Flowering Period: July, August, September

Also Called:

Lance-leaf ragweed.

Stems:

Erect, much branched, conspicuously rough-hairy, especially above; branches ascending.

Leaves:

Mostly alternate, lowermost sometimes opposite, sessile, simple, numerous, lanceolate to lance-linear, .4 to 2.8 inches long, 1/8 to 2/5 inch wide, usually with prominent pair of teeth on each side near base, occasionally un-lobed; surfaces green, rough-hairy, upper surface only sparsely hairy; tip tapering to point; base rounded to heart-shaped. Lowermost leaves are often gone by flowering.

Inflorescences:

Monoecious; staminate heads above pistillate heads in dense spikes; pistillate heads single or few clustered in axils of leaves subtending staminate spikes.

Flowers:

Greenish, inconspicuous, ray florets absent; staminate heads sessile; involucre slanting cup-shaped, 1/10 to 1/6 inch in diameter, 3- to 5-lobed; pistillate involucre bur-like, enclosing 1 floret, with spines in 1 to several rows.

Fruits:

Achene, nut-like, oblong, 1/5 to 1/3 inch long, 4-angled in cross-section, with stout beak and 4 longitudinal ridges terminating in short spines.

Habitat:

Open disturbed areas, pastures, roadsides, upland prairies, stream banks, woodland openings.

Distribution:

Principally southeast 1/4 of Kansas

Origin:

Native

Forage Value:

Seeds are eaten by turkeys.

Comments:

bidentata alludes to the leaves having two teeth or lobes below the middle. The pollen of southern ragweed may cause allergy symptoms.