Hazels are plants of the genus Corylus 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 (with the hornbeams and allied genera) into a separate family Corylaceae. The fruit of the hazel is the hazelnut.
A birch is a thin-leaved deciduous hardwood tree of the genus Betula (/ˈbɛtjʊlə/), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Red List of Threatened Species. They are typically short-lived pioneer species and are widespread in the Northern Hemisphere, particularly in northern areas of temperate climates and in boreal climates. Birch wood is used for a wide range of purposes.
A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated (as in Salix). 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.
Alders are trees of the genus Alnus in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.
An ectomycorrhiza (from Ancient Greek ἐκτός (ektós) 'outside' μύκης (múkēs) 'fungus' and ῥίζα (rhíza) 'root'; abbreviated EcM; pl. ectomycorrhizae or ectomycorrhizas) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobiont, and the roots of various plant species. The mycobiont is often from the phyla Basidiomycota and Ascomycota, and more rarely from the Zygomycota.
Ectomycorrhizae form on the roots of around 2% of plant species, usually woody plants, including species from the birch, dipterocarp, myrtle, beech, willow, pine and rose families. Research on ectomycorrhizae is increasingly important in areas such as ecosystem management and restoration, forestry, and agriculture.
Betula leopoldae is an extinct species of birch in the family Betulaceae. The species is known from fossil leaves, catkins, and inflorescences found in the early Eocene deposits of northern Washington state, United States, and similar aged formations in British Columbia, Canada. The species is placed as basal in Betula, either as a stem group species, or an early divergent species.
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.
Corylus avellana, the common hazel, is a species of flowering plant in the birch family Betulaceae. The shrubs usually grow 3–8 metres (10–26 feet) tall. The nut is round, in contrast to the longer filbert nut. Common hazel is native to Europe and Western Asia.
The species is mainly cultivated for its nuts. The name 'hazelnut' applies to the nuts of any species in the genus Corylus, but in commercial contexts usually describes C. avellana. This hazelnut or cob nut, the kernel of the seed, is edible and used raw, roasted, or ground into a paste. Historically, the shrub was an important component of the hedgerows used as field boundaries in lowland England. The wood was grown as coppice, with the poles used for wattle-and-daub building and agricultural fencing.