Cyanea grimesiana subsp. grimesiana is a shrub species growing 1–3.2 meters tall. It has unbranched or sparingly branched muricate stems (covered with short, sharp projections). The leaves are simple, alternate, and pinnately divided, with blades measuring 27–58 cm in length and 14–32 cm in width. Each blade has 9–12 lanceolate or occasionally narrowly elliptic segments per side, each 0.8–5 cm wide. The leaf segments have acuminate and apiculate apices, with glabrous upper surfaces and occasionally sparsely pubescent or muricate. The lower surfaces are typically glabrous or muricate along the midrib and seldom densely pubescent. Leaf margins are irregularly lobed to cleft, with muricate petioles and 8–32 cm long. It produces inflorescences of 6–12 flowers, with peduncles 15–75 mm long and pedicels 20–50 mm long. The flowers are perfect, with an obconical hypanthium 7–16 mm long and 3–8 mm wide. The calyx has five lobes, ovate to lanceolate in shape, 15–30 mm long and 4–10 mm wide, with a tube adnate to the ovary. The corolla is purplish or greenish to yellowish white, often with magenta suffusion or stripes, 55–80 mm long and 5–10 mm wide. It may be glabrous or sparsely pubescent, with an arcuate tube and spreading lobes that are ¼ to ½ the length of the tube. The stamens are five in number, alternating with the corolla lobes and forming a connate staminal column. Anthers may be glabrous or pubescent at the base, with all five typically having apical tufts of white hairs. The ovary is inferior and 2-celled, with an axile placentation and a 2-lobed stigma. The fruit is an orange obovoid to ellipsoid berry, 18–30 mm long and 8–15 mm wide, topped with persistent calyx lobes. The seeds are numerous, small, brown to black, smooth, and shiny, ca. 0.2–0.5(–2) mm long, with a straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It is found in mesic to wet forests at elevations ranging from 200-730 meters.