General: Birch family (Betulaceae.: Native shrubs or small trees growing 1-8(-15) meters tall, rhizomatous and forming colonial thickets; main stems (or trunk) straight, with spreading, ascending branches, the twigs light brown, sometimes with glandular hairs. Leaves are deciduous, alternate, nearly round to narrowly ovate or ovate-oblong, with a heart-shaped or rounded base, often nearly angular and slightly lobed near the tip, 4-10 cm long, blunt to broadly acute, doubly serrate, usually pubescent on major veins and in vein axils, the petiole with or without glandular hairs. Male (staminate) and female (pistillate) flowers are separate, but both types present on each plant (the species monoecious); male flowers numerous in long, pendulous stalks (catkins) 4-6 cm long, in clusters of 2-3 near branch tips, appearing in the fall but opening the following spring; female flowers: several in a scaly bud, tiny and inconspicuous with only bright red stigma and styles protruding from the otherwise gray-brown buds, almost completely enclosed by bracts, near the end of the twigs. Fruit is an acorn-like nut about 2 cm in diameter, completely concealed by two, leafy, coarsely toothed (husk-like) bracts fused at the tip and forming an extended tubular beak. The common name refers to the bracteal beak of the fruit; “hazel” from the Old English name for filbert.
Variation within the species: beaked hazelnut is divided into two distinct entities:
Corylus cornuta Marsh. var. cornuta
synonym: Corylus rostrata Ait.
Corylus cornuta var. californica (A. DC.) Sharp
synonym: Corylus californica Rose
synonym: Corylus rostrata var. californica A. DC.
synonym: Corylus cornuta var. glandulosa Boivin
Var. californica differs from var. cornuta in habit, leaf shape, the presence of glandular hairs, form and size of the involucre, geography, and other features, summarized in the contrast below.
1. Small to large shrubs; leaf blades ovate to narrowly elliptic, apex distinctly acuminate; twigs and petioles without glandular hairs; bracteal beak 2 times or more the fruit length.
…………..........………........... var. cornuta
1. Large shrubs or small trees; leaf blades nearly round or broadly elliptic, apex broadly acute to obtuse; twigs and petioles usually with glandular hairs; bracteal beak less than 2 times the fruit length.
................................................... var. californica
Preliminary studies of the beaked hazelnut complex world-wide, one North American species with two varieties or subspecies and one east Asian species with two varieties, indicate that Corylus cornuta var. cornuta is overall more similar in morphology to the east Asian C. sieboldiana Blume than to var. californica, suggesting that C. cornuta is better regarded as two separate species.
