Species: Arnica sororia Greene

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Arnica sororia Greene

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TAXONOMY

Family:

Asteraceae or Compositae

Genus:

Arnica

Species Synonyms:

Arnica fulgens var. sororia (Greene) G.W. Douglas & G. Ruyle-Douglas

Common Names:

twin arnica

DISTRIBUTION

Canada:

southern British Columbia, Alberta, southern Saskatchewan

Saskatchewan:

southwestern Saskatchewan; near Maple Creek

Ecoregion:

Mixed Grassland

RARITY STATUS

Provincial Status According
to Harms (2003):

Endangered

Nature Conservancy Status:

G4G5

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Arnica sororia endangered because of extreme rarity in Saskatchewan.

SPECIES DESCRIPTION

Height:

10 – 30 cm tall

Roots:

well-developed rhizomes

Stems:

unbranched, glandular-pubescent

Leaves:

basal and cauline; basal leaves persistent, several, petiolate or tapered to base, without tuft of brown wool in leaf axil, conspicuous nerves 3, midvein straw-coloured; cauline leaves opposite, sessile, (2) 4 – 8, to 5 cm long, to 0.8 cm wide, lanceolate, conspicuously 3-nerved, glandular-pubescent, margin entire

Inflorescence:

terminal, usually solitary, 2 – 3 cm broad; involucre 10 – 15 mm high, lanceolate, glandular-pubescent, greenish at base, lighter (occasionally light brown) at top; receptacle naked

Flowers:

ligulate and tubular florets; ligulate florets 10 – 23, yellow, ligule notched at tip, pistillate; tubular florets many, corolla stipitate-glandular, perfect, anthers yellow, style branches flattened

Fruits:

achene uniformly hairy; pappus white, barbellate, bristles capillary

ARNICA KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Rhizomes naked except for reduced scales at nodes; 5 – 10 pairs of cauline leaves; pappus straw-coloured or brown	A. chamissonis
1 Rhizomes with overlapping scales and leaf bases; 2 – 4 pairs of cauline leaves; pappus white	2

2 Basal leaves cordate or broadly ovate, usually long-petiolate	A. cordifolia
2 Basal leaves linear, lanceolate or oblanceolate, usually sessile	3

3 Lower leaves markedly denticulate or dentate; heads 4 or 5 (11)	A. loncophylla
3 Lower leaves entire or obscurely denticulate; heads 1 – few	4

4 Old basal leaf bases with a dense tuft of brown hairs in leaf axils	A. fulgens
4 Old basal leaf bases without a dense tuft of brown hairs in leaf axils	5

5 Plants more or less densely long villous-tomentose; midvein of basal leaves often reddish; stem leaves in 2 –3 pairs; head to 5 cm across; involucre purple-tipped; northern latitudes	A. angustifolia ssp. angustifolia
5 Plants glandular pubescent, not tomentose; midvein of basal leaves straw-coloured; stem leaves in 2 or 4 pairs; heads to 3 cm across; involucre not purple-tipped; prairies	A. sororia