Among the nuts that fit both the botanical and popular conception are the acorn, chestnut, and filbert; other so-called nuts may be botanically a seed (Brazil nut), a legume (peanut [groundnut]), or a drupe (almond and coconut).
Corylus contains about 15 species, including C. avellana (filbert, also known as hazelnut), distributed throughout the Northern Hemisphere.
Protective bactericidal sprays, paints, or drenches containing copper or antibiotics are used against bacterial blights of beans and celery, fire blight, crown gall, blackleg of delphinium, and filbert and walnut blights.
Corylus is the source of the filbert, or hazelnut, grown for many centuries in parts of Europe.
Choice nuts are produced by two Eurasian trees, the European filbert (Corylus avellana) and the giant filbert (C. maxima), and by hybrids of these species with two American shrubs, the American filbert (C. americana) and the beaked filbert (C. cornuta), popularly called hazelnuts.
This distinction was found to be misleading, and filbert became the common name for the genus in the U.S. The term cobnut is limited to a commercial variety of one species; the Jamaican cobnut has a similar flavour but is an unrelated plant of the family Euphorbiaceae.
It can be divided into two subfamilies: Betuloideae, with the genera Betula (birch) and Alnus (alder); and Coryloideae, with the genera Carpinus (hornbeam), Corylus (hazel, or filbert), Ostrya, and Ostryopsis.
Corylus is the source of the filbert, or hazelnut.
The large cobnut is a variety of the European filbert; Lambert's filbert is a variety of the giant filbert.
An oil from the European filbert is used in food products, perfumes, and soaps; the tree yields a soft, reddish white timber, useful for small articles such as tool handles and walking sticks.
Nuts produced by the Turkish filbert (C. colurna) are sold commercially as Constantinople nuts.
