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:

Achnatherum hymenoides, Calamovilfa sp., Chenopodium subglabrum, Elymus lanceolatus ssp. lanceolatus, Helianthus petiolaris, Psoralidium lanceolatum, Rumex venosus, Salsola kali, Shinnersoseris rostrata, Sporobolus cryptandrus

RARITY STATUS

Provincial Status According
to Harms (2003):

Vulnerable

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

Vulnerable

COSEWIC Status:

None

Ambrosia acanthicarpa 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 the sand dune areas.

SPECIES DESCRIPTION

Height:

15 – 60 cm tall

Roots:

fibrous

Stems:

decumbent, spreading, branched, woody, dark brown, sometimes purplish or with purple stripes, white hispid

Leaves:

alternate, may be opposite near base, lower leaves petioled, upper leaves sessile or nearly so, 5 – 10 cm long, ovate to lanceolate, twice pinnatifed, tips of lobes acute, coarsely strigose or scabrous hispid on both sides

Inflorescence:

monoecious; staminate heads in branched raceme; staminate involucre 3 – 9-lobed, white hispid; pistillate heads in leaf axils; pistillate involucre 5 – 10 mm long, with several rows of long spines

Flowers:

inconspicuous

Fruits:

burs glabrous 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 Involucre with several rows of long spines	A. acanthicarpa
1 Involucre with one row of short spines	2

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

3 Rootstalks running; leaves scabrous above; staminate involucres strigose-hispid; fruit nearly beakless, unarmed or with short, blunt tubercles	A. psilostachya
3 No running rootstalks; leaves nearly smooth above; staminate involucres glabrous or pilose; fruit with 4 – 7 sharp tubercles, subulate beak	A. artemisiifolia var. elatior