Rhizomes pale brown. Leaves: blade 2-pinnate with pinnatifid leaflets to 3-pinnate, occasionally 2-ternate; leaflets short- to long-petiolulate, blade ovate, deeply lobed or incised, margins sharply serrate. Inflorescences 2-3-flowered, often longer than leaves at anthesis, 8-12 cm, elongating to 35 cm in fruit. Flowers nodding; sepals reflexed and ascending, linear-lanceolate, 6-11(-15)× 0.3-1 mm; petals linear-lanceolate, nectary nearly basal, blade flattened, narrowly ligulate at apex; stamens 9-15. Follicles 6-10; stipe equal to or slightly longer than body; body oblong, 7-10 mm; beak recurved, less than 1mm. Seeds 1.8-2.2 mm. 2 n =18. Flowering spring. Moist, coniferous forests, seeps, and bogs; 0-1500m; B.C.; Alaska, Wash. Coptis aspleniifolia , C . laciniata , and C . occidentalis form a group of morphologically similar, allopatric species that are probably recently derived. The species may have originated in response to the opening of the western Cordilleran landscape after Pleistocene glaciation and could be considered localized variants of a single species. Although most individuals can be readily distinguished, some can be difficult to place.
A putative hybrid between Coptis aspleniifolia and C . trifolia has been found along the Kennedy River of Vancouver Island, British Columbia (T.C. Brayshaw, pers. comm.). It has 3-5 deeply dissected leaflets per leaf and no complete flowers.