The hazelnut plant (Corylus) is often misidentified as a small tree, though it is more commonly a large, multi-stemmed shrub. The visual difference between species is significant; native varieties often grow in thickets while cultivated types, sometimes called filberts, are trained into small trees. Identifying a hazelnut relies on observing its distinct habit, unique foliage, and reproductive structures.
Overall Structure and Bark Appearance
The typical hazelnut plant is characterized by its sprawling, multi-stemmed habit, growing as a large shrub that reaches heights of 10 to 20 feet. It often forms thick clumps, with multiple shoots emerging from the base rather than a single, dominant trunk. While some species, like the Turkish Hazel, can grow into a tree up to 65 feet tall, most common varieties are bushy and dense.
The bark provides a clear identifying feature, especially on mature stems. Young growth has smooth, grayish-brown bark. As the plant ages, this texture develops shallow fissures or a slightly peeling appearance. Older stems may develop a mild, criss-cross netted pattern while maintaining a light grayish-brown hue.
Identifying Features of the Leaves
Hazelnut leaves are a primary identification tool during the growing season due to their distinctive shape and texture. The foliage is arranged alternately along the stems and is broadly oval or nearly round. They feature a slightly pointed tip and a heart-shaped or rounded base where the leaf meets the stalk.
The margin of the leaf is distinctly double-serrated, giving it a jagged appearance. The surface is soft to the touch because of downy hairs, or pubescence, particularly on the underside. These simple leaves usually measure between two and five inches in length.
The Reproductive Cycle and Hazelnuts
The hazelnut plant is monoecious, bearing separate male and female flowers on the same plant. The male flowers are highly visible, appearing as long, pale yellow, pendulous structures called catkins. These catkins form in the autumn, hang throughout the winter, and release pollen in late winter or early spring before the leaves emerge.
The female flowers are far less conspicuous, appearing as tiny, bud-like structures. Only the bright red stigmas protrude, which are the receptive parts of the flower that catch wind-blown pollen. The resulting fruit is the hazelnut itself, which matures in late summer to early autumn.
The ultimate visual identifier is the nut’s involucre, or husk. This leafy material partially or completely encloses the developing nut, depending on the species. The husk is initially green and protects the nut until it ripens and turns brown.