Skip to main content

Ambrosia artemisiifolia - annual ragweed

Scientific Family
Asteraceae
Plant type
Forbs and Subshrubs
Origin
Native
Lifecycle
Annual
Similar species
Ambrosia acanthicarpa, A. psilostachya, A. confertiflora
Height
8 to 40 inches
Riparian
No

Stems upright, hairy, rough; leaves highly dissected, opposite attachment below, alternate above.

Annual; erect stems; leaves thin, fern-like, deeply lobed with many side lobes, lower leaves deeply lobed again (bipinnatifid) and attached opposite, upper leaves alternate attachment; flower heads along the length of slender, elongated spikes.

Habitat

Found on roadsides, in old fields and other waste places.

Plant Community
Disturbed Areas
Low elevation
5200
High elevation
8000

Flower Characteristics

Heads disc flowers; terminal spike-like male flower clusters 1 to 4 inches long, may have 2 short side spikes; female flowers sessile, single, 1/8 inch long, green, turning yellow-green and brown as it matures; female and male flowers in separate heads.

Flower color
Green, yellowish-green, brown
Flower shape
Inconspicuous
Tubular
No
First bloom month
August
Last bloom month
September
Flower clusters
None

Leaf and Stem Characteristics

Pinkish-red stems grooved and hairy; green leaves to 6 inches long, 4 inches wide, lower leaves opposite, upper alternate along the stem, deeply lobed, base much wider than the tip; margins smooth or toothed.

Leaf type
Compound
Leaf color
Green
Leaf shape
Pinnatifid
Leaf margin
Toothed
Leaf attachment
Alternate & Opposite
Leaves clasp
No
Leaf hairs
Leaves & stems
Spines
No

Fruit and Seed Characteristics

Woody with 4 to 7 spine-like projections, resembling a crown.

Fruit type
Achene
Fruit color
Brown

Numerous seeds per flower head, viable for up to 5 years.