Cyanea fissa is an unbranched or sparingly branched shrub that grows between 1 and 5 meters tall and produces yellow latex. The leaves are simple and alternately arranged. The blades are oblanceolate to obovate, measuring 32–80 cm long and 5–13 cm wide. The apex is acuminate to acute, while the base is attenuate, narrowing imperceptibly into a winged petiole. The upper surfaces are green and glabrous, whereas the lower surfaces are pale green and pubescent. The margins are minutely callose–denticulate. The petioles range from 0.5 to 4 cm in length and are winged. Stipules are absent. The flowers are arranged in axillary racemes, with each inflorescence containing 8–20 flowers. The inflorescences are pubescent, with peduncles measuring 20–60 mm long and pedicels 8–20 mm long. The hypanthium is obconical to obovoid, measuring 6–10 mm long and 4–6 mm wide, and is pubescent. The flowers are bisexual (perfect). The calyx has five triangular lobes to narrowly triangular, measuring 3–16 mm long and 1.5–2.5 mm wide, with an apex that is acute to acuminate. The lobes are distinct or rarely connate, and the calyx tube is adnate to the ovary. The corolla is zygomorphic (bilaterally symmetric), white or pale lilac, and longitudinally striped with purple. It measures 25–35 mm long and 4–5 mm wide and is densely pubescent. The corolla tube is gently curved, dorsally cleft to about the middle, with the lobes spreading. The five stamens alternate with the corolla lobes and are connate. The staminal column is glabrous, while the anthers are minutely papillose, with the lower two anthers having apical tufts of white hairs. The anthers are dithecal, opening by longitudinal slits, and are coherent but separate after anthesis or connate to form a tube into which pollen is shed. The filaments are distinct or connate above and are attached to the epigynous nectary disk or the base of the corolla, rarely adnate to the corolla tube. The ovary is inferior and two-celled, with axile ovule placentation. The stigma is two-lobed, remaining appressed and nonreceptive as the style grows through the anther tube, pushing out the pollen, after which the stigmas spread apart and become receptive. The fruit consists of reddish-orange berries that are broadly obovoid, measuring 13–20 mm long and 10–15 mm wide. The seeds are numerous, small, brown to black, smooth, and shiny, measuring 0.2–0.5(–2) mm long. Each seed has a straight, short to, spatulate dicotyledonous embryo embedded in oily endosperm. It is found in bogs, diverse mesic forests, and wet forests between 200-915 meters.