Perennials cespitose or colonial, 5–30 cm; with short, erect, woody caudices from long, thin rhizomes. Stems 1–8+, erect (purplish to brown, slender), villous, more densely so distally, distally moderately stipitate-glandular. Leaves (yellowish to dark green. midrib purplish, often prominent) thin, reduced distally, margins entire; basal withering by flowering, winged-petiolate to subpetiolate (petioles ± sheathing), blades narrowly oblanceolate, 8–15 × 1–3 mm, bases attenuate, margins scabrous, apices obtuse to acute, faces glabrous or glabrate; proximal cauline often withering by flowering, sessile or subsessile, blades linear-oblanceolate, 20–70 × 1–4 mm, bases ± clasping, margins ciliate, apices acute, abaxial faces glabrous or midnerve ± sparsely villous, adaxial glabrous or sparsely villous, midnerves ± villous; distal sessile, blades linear-lanceolate, 10–30 × 1–2.5 mm, bases ± subclasping, ± rounded to subauriculate, margins sometimes stipitate-glandular, apices acute, mucronate or white-spinulose, faces glabrous or sparsely villous, short-stipitate-glandular. Heads usually borne singly, sometimes in open, corymbo-paniculiform arrays, branches ascending. Peduncles ± densely short-villous, ± densely stipitate-glandular, bracts 1–3, foliaceous, reduced. Involucres campanulate, 7–10 mm. Phyllaries in 3–4(–5) series, linear-lanceolate, subequal, bases scarious, margins hyaline or purplish, scarious, erose, ciliate or short-stipitate-glandular, green zones herbaceous at least distally, often purplish to purple, apices long-acuminate, spreading to reflexed, faces ± densely villous (outer more so), ± densely stipitate-glandular. Ray florets (8–)15–30; corollas purple to blue, laminae 5–11 × 0.5–2 mm. Disc florets 16–38; corollas yellow becoming brown, 4–6.5 mm, lobes triangular, 0.4–0.8 mm. Cypselae brown (sometimes purplish, nerves stramineous), narrowly obovoid, ± compressed, ca. 3 mm, 7–10-nerved, faces sparsely to moderately sericeo-strigose; pappi sordid (barb tips sometimes purplish-tinged), 3.5–4.8 mm. 2n = 10.
Phenology: Flowering Jul–Aug.
Habitat: Mud flats, gravelly, stony or silty lakeshores, sometimes saline areas
Elevation: 300–1500 m
N.W.T., Yukon, Alaska.
Of conservation concern.
Symphyotrichum yukonense is distributed disjunctly on the John River in the southern Brooks Range (Alaska), Lake Kluane (Yukon), and the Mackenzie Mountains and middle Mackenzie River (Northwest Territories). It appears closely related to S. pygmaeum.