The hazel tree (Corylus) is a versatile plant often found in hedgerows and woodland borders across the Northern Hemisphere. It can appear as either a multi-stemmed shrub or a small tree. Identifying a hazel requires observing its unique combination of bark, foliage, and reproductive structures throughout the year.
Identifying Features of the Bark and Overall Shape
The hazel typically exhibits a multi-stemmed growth habit, often appearing more like a large, dense shrub than a single-trunked tree. While it can reach heights of 10 meters, it is frequently managed through coppicing. This management results in multiple straight shoots rising from the base, giving the plant a distinctive appearance.
The bark on young stems is smooth and shiny brown. As the plant matures, the bark transitions to grayish-brown, often developing shallow fissures or becoming slightly scaly. A unique identifying feature is the presence of pale yellow-green lenticels, or breathing pores, which appear as small marks across the surface of the younger bark. Younger branches also often display a slightly angular or zig-zag growth pattern, noticeable during the winter.
Distinct Characteristics of Hazel Leaves
Hazel leaves are reliable features for identification, noted for their broad, almost circular or broadly heart-shaped appearance. They are arranged alternately along the stem and have a clearly pointed tip. Mature leaves typically range from 6 to 12 centimeters long and wide.
The leaf margin is distinctly double-serrated. A defining tactile characteristic is the texture, as the leaves are covered in fine, downy hairs on both the top and underside, making them feel rough or fuzzy to the touch. When newly emerged in the spring, the leaves are a medium green color, providing dense foliage throughout the summer.
The Unique Appearance of Catkins and Nuts
Hazel trees produce separate male and female flowers on the same plant (monoecious). The male flowers are the most conspicuous, forming long, pendulous structures called catkins, which resemble “lamb’s tails” and are pale yellow. These catkins form in the autumn and are visible throughout the winter, elongating to 5 to 12 centimeters before releasing pollen in late winter or early spring, well before the leaves emerge.
The female flowers are much less noticeable, appearing as tiny, bud-like structures with only bright red, thread-like styles protruding. These styles are receptive to wind-borne pollen and can be found on the branch just above the male catkins. If successfully pollinated, the female flowers develop into the hazelnut, typically maturing between late summer and autumn. The nuts are contained within an involucre, a leafy, protective husk that partially or fully encloses the hard shell.