Hazelnut (Corylus americana), one of several related large shrubs known for their tasty nuts that provide food for humans or wildlife, is found throughout Ohio along roadsides, in fields, at the edges of forest, and in fencerows, in dry or moist sites. Also known as American Filbert or Hazel, it develops a broad, rounded, strongly suckering growth habit with age. Hybrids have been developed with European Filbert that combine its superior nut quality and yield with the cold hardiness of Hazelnut.
Hazelnut will reach dimensions of 15 feet tall and 15 feet wide, becoming arching and spreading with age, but new vertical suckers keep its middle interior canopy dense. As a member of the Birch Family, it is related to the Alders, Birches, Hornbeams, and Hophornbeams, in addition to other Hazelnuts and Filberts.
Planting Requirements - Hazelnut is very adaptable to moist or dry, reasonably well-drained soils of variable pH and variable soil quality. It is found in zones 4 to 9, in full sun to partial shade (best nut production occurs in full sun).
Potential Problems - Hazelnut has several diseases and pests that may affect its bark or foliage, but none are usually serious.
Identifying Features - Hazelnut
Hazelnut leaves are alternate, serrated, short-petioled, and normally broadly ovate to broadly elliptical, but can also be broadly obovate.
While Hazelnut is a healthy and vigorous shrub, any plant at times can be infested with diseases or pests, most of which render no long-term damage to the plant, such as feeding caterpillars.
As with many woody plants, floral buds form in early to mid summer for the following year's spring flowers, and overwinter in the immature dormant state. Such is the case with the monoecious flowers of Hazelnut.
Small green catkins (male flowers) form in summer.
The catkins turn brown and grow in winter. They expand in late winter and early spring, turning yellow, often with a miniature reddish-brown female flower nearby.
A few of the female flowers give rise to fruits wrapped in an outer, papery husk that covers one inner nut that serves as a food source for many mammals, maturing in early autumn.
Hazelnut is characterized by many vertical shoots that are sparsely branched. As these grow upright, they also arch outward for a rounded overall shape and expose the shiny, olive-brown, heavily lenticeled bark of the branches and trunks.