Description from Flora of China
Cirsium diamantiacum (Nakai) Nakai; C. japonicum Candolle var. litorale (Maximowicz) Kitamura; C. litorale Maximowicz; C. litorale var. nudum Regel; C. maackii Maximowicz var. spiniferum Nakai; C. pendulum Fischer ex Candolle var. oligocephalum Regel & Tiling; Cnicus diamantiacus Nakai; C. japonicus (Candolle) Maximowicz var. schantarensis (Trautvetter & C. A. Meyer) Maximowicz.
Herbs 70-120 cm tall, perennial. Stems erect, diffusely branched above, unwinged, with sparse long multicellular hairs. Leaves concolorous, green, surface smooth, glabrous or with sparse multicellular hairs. Basal leaves withered at anthesis. Lower and middle cauline leaves petiolate; petiole base auriculate semiamplexicaul, margin winged and spiny or with spiny teeth; leaf blade elliptic, ± narrowly ovate to triangular-lanceolate, 14-27 × 8-12 cm, pinnately divided; segments 4-8 pairs, obliquely triangular, lanceolate, or broadly linear, fringed with spinules; terminal segment lanceolate. Upper cauline leaves sessile, progressively smaller, pinnately lobed or uppermost ones undivided, amplexicaul. Peduncles long. Capitula few, terminal, nodding. Involucre campanulate, ca. 2 cm in diam., glabrous or sparsely cobwebby. Phyllaries imbricate, in ca. 6 rows, lacking marginal spinules, wings, and scarious appendage, abaxially with or without a resinous gland; outer and middle phyllaries triangular to ovate-triangular, 5-8 × 1.5-2 mm, apex narrowed into a ca. 1 mm spinule; inner phyllaries lanceolate to linear-lanceolate, 10-12 × ca. 2 mm, apex narrowed into a soft spinule and scarious. Florets bisexual. Corolla purplish red, ca. 1.6 cm, tube ca. 5 mm. Achene yellowish, ca. 4.5 mm. Pappus bristles brownish, ca. 1.6 cm. Fl. and fr. Jun-Sep. 2n = 34.
Forests, forest margins, along rivers, meadows; 1500-2000 m. Heilongjiang, Jilin, Liaoning [Russia].