G. shallon is 0.2 to 5 m (0.66 to 16.40 ft) tall, sprawling to erect. Evergreen, its thick, tough, egg-shaped leaves are shiny and dark green on the upper surface, and rough and lighter green on the lower. Each finely and sharply serrate leaf is 5 to 10 cm (2.0 to 3.9 in) long. The inflorescence consists of a bracteate raceme, one-sided, with five to 15 flowers at the ends of branches. Each flower is composed of a deeply five-parted, glandular-haired calyx and an urn-shaped pink to white, glandular to hairy, five-lobed corolla, 7 to 10 mm (0.28 to 0.39 in) long. The reddish to blue, rough-surfaced, hairy, nearly spherical fruit is 6 to 10 mm (0.24 to 0.39 in) in diameter.