Diphylleia is a small genus of large perennial herbs in the family Berberidaceae (order Ranunculales), formally described by André Michaux in 1803 in his Flora Boreali-Americana. The genus comprises just three species distributed across widely disjunct temperate regions: one in the southern Appalachians of eastern North America, one in northern Japan, and one in montane China — a classic example of the Eastern Asian–Eastern North American floristic disjunction.
Plants are deciduous, growing to about 1.2 metres tall, with rhizomes that produce a single leaf or flowering shoot each year. The leaves are the genus's most distinctive feature: large, simple, and deeply 2-parted, with palmately veined blades that can reach 47 cm across, with prominently toothed margins. Non-flowering shoots bear a single basal leaf with a centrally attached (peltate) petiole; flowering shoots carry two alternate cauline leaves with the petiole attached near the blade margin.
Flowers are small (8–20 mm), white, and arranged in terminal cymes or umbel-like clusters. Each flower has 6 early-falling sepals, 6 white petals, and 6 stamens whose anthers open by two apically hinged flaps — an unusual mechanism shared with related genera such as Berberis. Fruits are striking dark blue, glaucous berries containing 2–11 red seeds.
Diphylleia grayi, known as the skeleton flower, is perhaps the most celebrated member of the genus: its white petals become fully translucent when wet, reverting to white as they dry — an adaptation that has made it a popular subject in photography and cultivation. Diphylleia cymosa (umbrella leaf) is native to moist forest understories in the southern Appalachians, while Diphylleia sinensis occupies similar shaded, moist habitats in several Chinese provinces.
Etymology
The name Diphylleia derives from the Greek dis (twice) and phyllon (leaf), a reference to the paired leaves borne on the flowering shoots — a defining feature noted by Michaux when he described the genus in 1803.
Distribution
The three species of Diphylleia occupy widely disjunct temperate ranges: D. cymosa is confined to the southern Appalachian Mountains from southwestern Virginia to northwestern Georgia; D. grayi grows at Cape Sōya in northern Japan; and D. sinensis occurs in the Chinese provinces of Gansu, Hubei, Shaanxi, Sichuan, and Yunnan. This pattern of eastern North American and eastern Asian disjunction is shared with many other woodland herb genera.
Ecology
All three species grow as woodland understory herbs in moist, shaded habitats — forest floors, streambanks, and shaded ravines in temperate montane regions. The rhizomatous growth habit and annual increment pattern reflect adaptation to seasonal dormancy in deciduous forest environments.
