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
 
Twin arnica is imperiled because of extreme rarity in Saskatchewan.
 
SPECIES DESCRIPTION
 
Height: 10 – 30 cm tall
Roots: rhizomes well-developed
Stems: unbranched, glandular-hairy
Leaves: basal and on the stem; basal leaves persistent, several, stalked or tapered to base, without tuft of brown wool in axil, conspicuous nerves 3, midvein straw-coloured; stem leaves opposite, sessile, (2) 4 – 8, to 5 cm long, to 0.8 cm wide, lance-shaped, conspicuously 3-nerved, glandular-hairy, margin entire
Inflorescence: terminal, usually solitary, 2 – 3 cm broad; involucre 10 – 15 mm high, lanceolate, glandular-hairy, greenish at base, lighter (occasionally light brown) at top; receptacle naked
Flowers: ray and disc flowers; ray flowers 10 – 23, yellow, petal notched at tip, female; disc flowers many, petals with glands, perfect, anthers yellow, style branches flattened
Fruits: achene uniformly hairy; pappus white, barbed, bristles capillary
 
ARNICA KEY FOR SPECIES FOUND IN SASKATCHEWAN
 
1 Rhizomes naked except for reduced scales at nodes; 5 – 10 pairs of stem leaves; pappus straw-coloured or brown
A. chamissonis
1 Rhizomes with overlapping scales and leaf bases; 2 – 4 pairs of stem leaves; pappus white
2
   
2 Basal leaves cordate or broadly oval, usually long-stalked
A. cordifolia
2 Basal leaves linear, lance-shaped or inversely lance-shaped, usually sessile
3
 
3 Lower leaves markedly toothed, heads 4 or 5 (11)
A. loncophylla
3 Lower leaves entire or obscurely toothed, 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 hairy; midvein of basal leaves often reddish; stem leaves in 2 – 3 pairs; head to 5 cm across; bracts purple-tipped; northern latitudes
A. angustifolia ssp. angustifolia
5 Plants glandular hairy, not long hairy; midvein of basal leaves straw-coloured; stem leaves in 2 or 4 pairs; heads to 3 cm across; bracts not purple-tipped; prairies
A. sororia