Species: Ambrosia acanthicarpa Hook.

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Ambrosia acanthicarpa Hook.

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TAXONOMY

Family:

Asteraceae or Compositae

Genus:

Ambrosia

Species Synonyms:

Gaertneria acanthicarpa (Hook.) Britt.
Franseria acanthicarpa (Hook.) Coville

Common Names:

bur ragweed
annual bursage
bursage ragweed
flatspine burr ragweed
sand bursage
franseria

DISTRIBUTION

Canada:

southern Alberta – southwestern Manitoba

Saskatchewan:

southern Saskatchewan; Cypress Hills, Great Sand Hills, Elbow Sand Hills

Ecoregion:

Cypress Upland, Mixed Grassland, Moist Mixed Grassland

HABITAT

Saskatchewan:

dry, active to semi-stabilized sand dunes

Associated Species:

beaked skeletonweed, dune scurfpea, Indian rice grass, prairie sunflower, Russian thistle, sand dropseed, sand reed, smooth goosefoot, veiny dock, wheatgrass

RARITY STATUS

Provincial Status According
to Harms (2003):

Vulnerable

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

Vulnerable

COSEWIC Status:

None

Bur ragweed is vulnerable in Saskatchewan because it is regionally restricted. In addition, some local populations are small. The sand dune habitat in which this species grows is fragile and may be damaged by developments or human use of sand dune areas.

SPECIES DESCRIPTION

Height:

15 – 60 cm tall

Roots:

fibrous

Stems:

reclining, spreading, branched, woody, dark brown, sometimes purplish or with purple stripes, hairs stiff and white

Leaves:

alternate, may be opposite near base, lower leaves stalked, upper leaves sessile or nearly so, 5 – 10 cm long, oval to lance-shaped, twice pinnately lobed, tips of lobes acute, coarsely hairy with stiff, sharp appressed hairs or rough, stiff hairs on both sides

Inflorescence:

male and female heads on the same plant; male heads in branched a elongated inflorescence with flowers maturing from the bottom upwards; bracts 3 – 9-lobed, stiffly white-hairy; female heads in leaf axils; bracts 5 – 10 mm long

Flowers:

inconspicuous

Fruits:

burs hairless except for minute glands; spines 8 – 15 in several rows, thin, weak, tips strait or slightly recurved; pappus absent

AMBROSIA KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Bracts with several rows of long spines	A. acanthicarpa
1 Bracts with one row of short spines	2

2 Leaves mostly long-stalked, 3 – 5-lobed or undivided, all opposite; bracts on male heads 3-ribbed; body of fruit ~5 mm	A. trifida
2 Leaves sessile or short-stalked, pinnately lobed, lower opposite, upper alternate; bracts on male heads radiately veined	3

3 Rootstalks running; leaves stiff-hairy above; bracts on male heads with stiff, appressed hairs; fruit nearly beakless, unarmed or with short, blunt nodules	A. psilostachya
3 Running rootstalks absent; leaves nearly smooth above; bracts on male heads hairless or with long, stiff straight hairs; fruit with 4 – 7 sharp nodules, beak awl-shaped	A. artemisiifolia var. elatior