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Asteraceae
Ambrosia

not marked as a favorite taxon Ambrosia trifida Linnaeus. Common name: Giant Ragweed, Riverweed, Hogweed. Phenology: Jul-Nov. Habitat: Floodplains, moist pastures; disturbed ground. Distribution: Nova Scotia and British Columbia south to n. peninsular Florida, Panhandle Florida, Texas, and California.

Glossary (beta!)

Origin/Endemic status: Native

Other Comments: The distinction between var. trifida and var. texana (or at the specific rank A. trifida and A. aptera) warrants additional study. Basionym: Ambrosia trifida L. 1753

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Heliophily ⓘ: 9

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Horticultural Information

NCBG trait

Intro: Erect, tap-rooted annual of floodplains, moist pastures and disturbed ground.

Stems: Stems stout, freely branched, covered with white hairs.

Leaves: Leaves opposite, petiolate (often with wings), broadly oval to elliptic with long-pointy tips, 3-12 in. long, often palmately divided into 3-5 lobes, toothed and rough-surfaced.

Inforescence:

Flowers: Male (staminate) flowers in tiny, nodding, saucer-shaped heads less than 1/4 in. wide and arranged in terminal spikes 3-6 in. long; female (pistillate) flowers tiny, in axils of upper, bract-like leaves. All lack petals and sepals.

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Height: 3-12 ft.

plant sale text:

bloom table text:

description: Erect, tap-rooted annual of floodplains, moist pastures and disturbed ground.

stems: Stems stout, freely branched, covered with white hairs.

leaves: Leaves opposite, petiolate (often with wings), broadly oval to elliptic with long-pointy tips, 3-12 in. long, often palmately divided into 3-5 lobes, toothed and rough-surfaced.

inflorescence:

flowers: Male (staminate) flowers in tiny, nodding, saucer-shaped heads less than 1/4 in. wide and arranged in terminal spikes 3-6 in. long; female (pistillate) flowers tiny, in axils of upper, bract-like leaves. All lack petals and sepals.

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