Duration: Annual

Nativity: Non-Native

Lifeform: Forb/Herb

General: Herbaceous, weedy annuals, to 100 cm tall, stems erect, herbage with both long and short appressed hairs.

Leaves: Bipinnasect, alternate or opposite, to 11 cm long, petiolate, at least on the lower leaves, the upper leaves sometimes sessile, surfaces covered with long white hairs.

Flowers: Staminate and pistillate, staminate corollas yellow, rarely purplish-red, involucres short-hairy and glandular, 2-5 mm broad, more or less saucer-shaped with 5-12 crenate lobes, receptacles with narrowly linear scales, filaments monadelphous, pistillate heads without corollas, involucres nutlike, usually with tubercles or spines near the apex, staminate heads borne above the pistillate ones in spikes or racemes to 20 cm long, 4-8 cm wide, usually nodding, pistillate heads axillary, few, 1-flowered, the involucres to 2 mm, corollas and pappus absent.

Fruits: Involucre in fruit becoming obovoid, 4-5 mm, weakly angled, with 7-8 mm spinose teeth and a short central beak to 2 mm long, surfaces glandular-pubescent. Seeds achenes.

Ecology: Unknown

Distribution: According to USDA PLANTS, this species occurs only in Louisiana.

Notes: Look to the slender, simple, stems, the small, usually linear leaves, and the simple spikes of the inflorescences to help identify this species, which have light green heads, the bracts united to form a fruit with a few very short teeth, and with a central beak.

Ethnobotany: Plant used to facilitate delivery of the placenta after childbirth. Roots used as a staple crop and stalks eaten as greens in the summer. Herb mixed with tobacco.

Etymology: Ambrosia is Greek for food of the gods, while tenuifolia means means slender leaved.

Synonyms: None

Editor: LCrumbacher 2012