Symphyotrichum yukonense (Cronquist) G.L. Nesom Asteraceae Synonyms: Aster yukonensis
Global Distribution: Endemic to Alaska, Yukon, and Northwest Territories.
Alaska Distribution: Arctic Tundra, Intermontane Boreal.
Ecoregions Occupied: Brooks Range, Kobuk Ridges and Valleys.
Conservation Status: S3 G3; BLM Watch.
Description191
Ray florets purple to Involucres 7 to 10 mm long, lavender, disc florets densely covered with glandular yellow hairs
Upper stem leaves linear to narrowly lanceolate, 1 to 3 cm long, 1 to 2.5 mm wide
Stems erect, 5 to 30 cm long, covered with glandular hairs in upper half
Lower stem leaves linear to narrowly oblanceolate, 2 to 7 cm long, 1 to 4 mm wide
Illustration by Valerie Ford, courtesy of Canadian Science Publishing 315
Symphyotrichum yukonense
General: Perennial herb from short, woody caudexes and long, thin rhizomes; forming tufts or colonies; stems 1 to 8, erect, purple to brown, slender, 5 to 30 cm long, villous, glandular hairs present in upper half.
Leaves: Basal leaves withering by time of flowering, linear to narrowly oblanceolate, 8 to 15 mm long, 1 to 3 mm wide, glabrous; lower stem leaves often withering by flowering, sessile with clasping bases, linear to narrowly oblanceolate, 2 to 7 cm long, 1 to 4 mm wide, glabrous or sparsely villous; upper stem leaves sessile, linear to narrowly lanceolate, 1 to 3 cm long, 1 to 2.5 mm wide, glabrous or sparsely villous, often covered with glandular hairs.
Flowers: Peduncles densely villous, densely covered with glandular hairs; flowers usually borne singly, sometimes several in open arrays; involucres 7 to 10 mm long; involucral bracts in 3 to 4 rows, linear, margins translucent or purple, densely villous, densely covered with glandular hairs; ray florets purple to lavender, 5 to 11 mm long, 0.5 to 2 mm wide; disc florets yellow.
Fruits: Achenes brown, narrowly obovoid, 3 mm long; pappi tan, 3.5 to 4.8 mm long.
© Bruce Bennett 2007
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Symphyotrichum yukonense
Ecology
Elevation: Most occurrences in Alaska are known from 40 to 380 m; an occurrence from Oolah Valley in the Brooks Range is at an elevation of approximately 1,580 m.
Landform: River bars, river terraces, floodplains, sand blowouts, sand dunes, stream beds.
Soil Type: Sand, silt, gravel.
Moisture regime: Usually moist to wet; also known from dry sites.
Slope: Flat to gently sloped.
Aspect: No particular aspect.
Vegetation type: Sparsely vegetated, open willow shrub, open graminoid- willow shrub, open forb-willow shrub.
Associated species: Arctous rubra, Artemisia furcata, Astragalus alpinus, Betula glandulosa, Calamagrostis canadensis, Calamagrostis purpurascens, Dasiphora fruticosa ssp. floribunda, Dryas ajanensis, Dryas integrifolia, Equisetum arvense, Eurybia sibirica, Hulteniella integrifolia, Lupinus arcticus, Papaver walpolei, Parnassia palustris, Picea glauca, Populus balsamifera, Oxytropis kobukensis, Salix alaxensis, Salix niphoclada, Saxifraga oppositifolia, Shepherdia canadensis.
Longevity: Perennial, longevity unknown.
Phenology: Flowering July through late August; fruiting through mid-September.
Population estimate: There are 39 known occurrences in Alaska; populations range in size from 20 individuals to locally abundant.
Herbivory: Seeds likely consumed by insect larvae.
Similar Species191, 192
Symphyotrichum yukonensis is easily confused with Symphyotrichum pygmaeum and Eurybia sibirica. The morphological features that distinguish these three species are shown in the table below.
Species Stems Stem leaves Involucres 5 to 30 cm long, Lower leaves 1 to 4 7 to 10 mm long, Symphyotrichum erect, covered mm wide, upper densely covered yukonense with glandular leaves 1 to 2.5 mm with glandular hairs wide hairs 1.5 to 15 cm long, Lower leaves 3 to 10 9 to 12.5 mm long, decumbent to Symphyotrichum mm wide, upper sparsely covered ascending, pygmaeum leaves 2 to 4 mm with glandular lacking glandular wide hairs hairs 5 to 60 cm long, Lower leaves 3 to 35 6 to 9 mm long, decumbent to mm wide, upper Eurybia sibirica glandular hairs erect, lacking leaves 1 to 12 mm absent glandular hairs wide
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Symphyotrichum yukonense
© Bruce Bennett 2007
© Rob Lipkin
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