Korea Flora: Deciduous shrub. Height 2-5m. Winter buds and branchlets: Spathulate, 4-5 scales, terminal and lateral buds similar in size (4-8mm long). New branches with white hairs. Leaf scars small, semi-lunar or triangular. Leaves alternate, broadly spathulate, with very distinct lobes in upper portion, 6.5-0.5(10.5)cm × 5.5-7.5cm, apex abruptly pointed (some resembling Corylus sieboldiana leaves). Base cordate with 7-9 pairs of lateral veins and double serration, fine hairs on upper surface and veins of lower surface. Petiole 1-3cm long, with fine hairs. Flowers monoecious. Male catkins in groups of 2-5. Fruit and Seeds: Involucre 40-50mm long, terminal teeth 5-14mm deeply divided with relatively wide tube. Dense brown hairs at base and many lobes at tip. Nut ovoid, about 15mm in diameter.

Sporophyte chromosome number 22.
Flowering period: March
Fruiting period: October
Distribution: Northern and Northeast China, parts of Far East Russia; throughout Korea (except some southern coastal areas)

Taxonomic notes: While Corylus heterophylla is widely distributed throughout the Korean Peninsula, Russia, and Northeast China, C. sieboldiana is restricted to all of Japan and the southern coast of Korea. Although C. heterophylla is recognized as a species in China and Russia due to its deeply lobed leaves, in Jeollanam-do areas bordering the southern coast, individual plants can show characteristics of both C. heterophylla and C. sieboldiana. Therefore, it is more appropriate to treat it as a variety based on leaf morphology rather than reproductive characteristics. Ohba (2006) distinguishes C. sieboldiana by its mature fruit involucre narrowing at the tip, while C. heterophylla's involucre does not narrow. However, involucre characteristics are highly variable, and specimens with narrowing tips are also found in the widely distributed C. heterophylla in Korea. Meanwhile, var. brevirostris C.K. Schneid., characterized by short involucres, is considered a common individual variation in C. sieboldiana and is not recognized as a variety. In Japanese herbarium surveys, C. heterophylla specimens were rarely seen. Claims about its distribution in central-northern Honshu and Hokkaido (Ohba, 2006) need review.