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.
A nut is a fruit consisting of a hard or tough nutshell protecting a kernel which is usually edible. In general usage and in a culinary sense, a wide variety of dry seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent).
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. A cob is roughly spherical to oval, about 15–25 mm long and 10–15 mm in diameter, with an outer fibrous husk surrounding a smooth shell, while a filbert is more elongated, being about twice as long as its diameter. The nut falls out of the husk when ripe, about seven to eight months after pollination. The kernel of the seed is edible and used raw or roasted, or ground into a paste. The seed has a thin, dark brown skin, which is sometimes removed before cooking.
The hazel (Corylus) is a genus of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae. The fruit of the hazel is the hazelnut.
Corylus avellana, the common hazel, is a species of flowering plant in the birch family Betuliaceae. It is native to Europe and western Asia. It is an important component of the hedgerows that were the traditional field boundaries in lowland England. The wood was traditionally grown as coppice, the poles cut being used for wattle-and-daub building and agricultural fencing.
Salix purpurea, the purple willowpurpleosier willow or purple osier, is a species of willow native to most of Europe and western Asia north to the British Isles, Poland, and the Baltic States.
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. It is also found growing wild in the forests of Western Himalayan range in the north Indian state of Himachal Pradesh particularly in the temperate regions of districts of Kullu, Shimla, Kinnaur district and Chamba district.
Corylus cornuta, the beaked hazelnut, is a deciduous shrubby hazel with two subspecies found throughout most of North America. The Eastern beaked hazel is found from southern Canada south to Georgia, while the Western beaked hazel occurs along the west coast from Alaska to California.
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.
Carpinus caroliniana, the American hornbeam, is a small hardwood tree in the genus Carpinus. American hornbeam is also known as blue-beech, ironwood, musclewood and muscle beech. It is native to eastern North America, from Minnesota and southern Ontario east to Maine, and south to eastern Texas and northern Florida. It also grows in Canada. It occurs naturally in shaded areas with moist soil, particularly near the banks of streams or rivers, and is often a natural constituent understory species of the riverine and maritime forests of eastern temperate North America.
Anisogramma anomala is a plant pathogen that causes a disease known as Eastern filbert blight on Corylus spp. (hazelnut). Also known as EFB.
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.
Ostrya carpinifolia, the European hop-hornbeam, is a tree in the family Betulaceae. It is the only species of the genus Ostrya that is native to Europe.
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.
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 ferox, the Himalayan hazelnut or Tibetan hazelnut, is a species of hazel native to the Himalayas of eastern Asia.
