Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams, numbering a total of 167 species. They are mostly natives of the temperate Northern Hemisphere, with a few species reaching the Southern Hemisphere in the Andes in South America. Their typical flowers are catkins and often appear before leaves.
Hornbeams are hardwood trees in the plant genus Carpinus in the family Betulaceae. Its species occur across much of the temperate regions of the Northern Hemisphere.
In botany, a nut is a fruit from a tree consisting of a hard or tough nutshell protecting a kernel which is usually edible. The shell is indehiscent, meaning it does not open to release the seed. Most seeds come from fruits that naturally free themselves from the shell, but this is not the case in nuts such as hazelnuts, chestnuts, and acorns, which have hard shell walls and originate from a compound ovary.
The hazelnut is the fruit of the hazel tree and therefore includes any of the nuts deriving from species of the genus Corylus, especially the nuts of the species Corylus avellana. They are also known as cobnuts or filberts according to species.
Corylus avellana, the common hazel, is a species of flowering plant in the birch family Betulaceae. The shrubs usually grow 3–8 metres tall. The nut is round, in contrast to the longer filbert nut. Common hazel is native to Europe and Western Asia.
Corylus maxima, the filbert, is a species of hazel in the birch family Betulaceae, native to southeastern Europe and southwestern Asia.
A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated. It contains many, usually unisexual flowers, arranged closely along a central stem that is often drooping. Catkins are found in many plant families, including Betulaceae, Fagaceae, Moraceae, and Salicaceae.
Corylus colurna, the Turkish hazel or Turkish filbert, is a deciduous tree native to southeast Europe and southwest Asia, from the Balkans through northern Turkey to northern Iran.
Corylus cornuta, the beaked hazelnut, is a deciduous shrubby hazel with two subspecies found throughout most of North America.
Ostryopsis is a small genus of deciduous shrubs belonging to the birch family Betulaceae. The species have no common English name, though hazel-hornbeam has been suggested, reflecting their similarities to the closely related hazels and hop-hornbeams.
Gevuina avellana, commonly known as the Chilean hazelnut or Gevuina hazelnut, is an evergreen tree growing up to 20 meters tall. It is the only species currently classified in the genus Gevuina. It is native to southern Chile and adjacent valleys in Argentina. It is found from sea level to 700 meters above sea level. Its distribution extends from 35° to 44° south latitude. The composite leaves are bright green and toothed, and the tree is in flower between July and November. The flowers are very small and beige to whitish, are bisexual and group two by two in long racemes. The fruit is a dark red nut when young and turns black. The peel is woody. It can grow up straight or branched from the soil, making up either a tree or a shrub.
Corylus heterophylla, the Asian hazel, is a species of hazel native to eastern Asia in northern and central China, Korea, Japan, and southeastern Siberia.
Corylus americana, the American hazelnut or American hazel, is a species of deciduous shrub in the genus Corylus, native to the eastern and central United States and extreme southern parts of eastern and central Canada.
Corylus johnsonii is an extinct species of hazel known from fossil fruits found in the Klondike Mountain Formation deposits of northern Washington state, dated to the early Eocene Ypresian stage. Based on described features, C. johnsonii is the oldest definite species in the genus Corylus.
Corylus chinensis, common names Chinese filbert and Chinese hazel, is a deciduous tree native to western China. This tree is considered vulnerable due to its rarity.
Phytoptus avellanae is an acarine gall-mite species inducing big bud galls of up to 10 millimetres (0.39 in) across, sometimes slightly open, on the buds of hazel and on filbert. Synonyms include Phytocoptella avellanae, Eriophyes avellanae, Calycophthora avellanae, Phytoptus coryli, Phytoptus pseudogallarum, and Acarus pseudogallarum. The mites are white, about 0.3 mm long, with numerous tergites and sternites. Two forms of P. avellanae exist, a gall causer and a vagrant form that has a more complex life-cycle and does not form galls.
Coryloides is an extinct genus of flowering plants in the hazelnut family, Betulaceae, containing the single species Coryloides hancockii. The species is solely known from the middle Eocene sediments exposed in north central Oregon and was first described from a series of isolated fossil nuts in cherts.
Corylus jacquemontii is a species of hazel, found in Asia, within the Himalayas and from Afghanistan through to W. Nepal. It is a small tree or shrub, with grey bark, ovate or obovate (teardrop-shaped) leaves, small flowers and small edible nuts, grouped in small clusters.
