Description from Flora of China
Blechnum japonicum Linnaeus f., Suppl. Pl. 445. 1782; Woodwardia affinis Ching & P. S. Chiu; W. intermedia Christ; W. japonica var. contigua Ching & P. S. Chiu; W. omeiensis Ching ex P. S. Chiu.
Rhizome decumbent, dark brown, stout, 3-5 cm in diam., densely scaly; scales dark brown, lanceolate or linear-lanceolate, ca. 1.5 cm, membranous, entire, apex acuminate, sometimes fibriform. Stipes close, 15-70 cm, 5-8 mm in diam., base densely scaly; upper part of stipe and rachis sparsely covered with brown, fibriform scales; lamina bipinnatifid, elliptic or lanceolate, 25-85 × 18-45 cm, leathery, apex acuminate; pinnae 7-15 pairs, subsessile or shortly stalked, broadly lanceolate; middle pinnae 12-25 × 2-4 cm, base acroscopically truncate, basiscopically rounded, margin cut 1/2 way to costa, apex acuminate; lobes 11-16 pairs, close, oblique, hemielliptic or hemiovate, lowest pair shortened, basiscopic lobe rounded, ovate or auriculate, 5-10 mm, apex rounded; middle lobes 1.3-2.2 × 0.7-1 cm, margin serrulate, apex acute; veins anastomosing with 2 or 3 rows of areoles along costae and costules, distally free, simple or forked. Sori occupying costular areoles, discrete, linear, sunken; indusia brown. 2n = 68.
Woodwardia japonica is variable in the length, number, and arrangement of the pinnae and in the shape of the pinna lobes.
Ridges, exposed slopes, shaded forests; 300-1500 m. Widely distributed south of the Chang Jiang and in Taiwan [Japan, Korea, Vietnam].