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 Corylus subsp. var.  Hazel
Flowering Common Hazel in early spring
Habit: shrub
Height: to
Width: to
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Lifespan: perennial
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USDA Zones: to
Sunset Zones:
Flower features:
Betulaceae > Corylus var. ,

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The hazels are a genus of about ten species of deciduous trees and large shrubs native to the temperate northern hemisphere.

Leaves and nuts of Turkish Hazel: note the spiny involucres (husks) surrounding the nuts

The scientific name is Corylus (authentic Latin but derived from an ancient Greek name), and it is placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.

They have simple, rounded leaves with double-serrate margins. The flowers are produced very early in spring before the leaves, and are monoecious, with single-sex catkins, the male pale yellow and 5–12 cm long, the female very small and largely concealed in the buds, with only the bright red 1–3 mm long styles visible. The seeds are nuts 1–2.5 cm long and 1–2 cm diameter, surrounded by an involucre (husk) which partly to fully encloses the nut; the shape and structure of the involucre are important in the identification of the different species of hazel.

The nuts obtained from the Common Hazel (Corylus avellana) are the common edible hazelnuts. This large shrub is grown extensively for its nuts. Nuts are also harvested from some of the other species, including the Filbert, from the closely related Balkan species Corylus maxima.

The Turkish Hazel (C. colurna) is widely cultivated as an ornamental tree in Europe and North America; this tree species does not conform to the typical stereotype of hazels as being shrubs, being up to 35 m tall with a single straight, stout, trunk up to 1.5 m in diameter. It is very tolerant of difficult growing conditions in urban situations, which has increased its popularity in civic planting schemes in recent decades.

A number of ornamental cultivars of the Common Hazel and Filbert are grown in gardens, including forms with contorted stems (C. avellana 'Contorta', popularly known as "Harry Lauder's walking stick" from its gnarled appearance); with weeping branches (C. avellana 'Pendula'); and with purple leaves (C. maxima 'Purpurea').

Standard Cyclopedia of Horticulture

Corylus (ancient Greek name). Betulaceae. Hazel. Filbert. Cobnut. Woody plants grown for their handsome rather large foliage and some species for their edible nuts.

Deciduous shrubs, rarely trees: lvs. alternate, stipulate, petioled, serrate and usually more or less pubescent: fls. monoecious, appearing before the lvs.; staminate in long, pendulous catkins, formed the previous year, and remaining naked during the winter (Fig. 1073), each bract bearing 4 divided stamens; pistillate included in a small, scaly bud with only the red styles protruding (Fig. 1074): fr. a nut, included or surrounded by a leafy involucre, usually in clusters at the end of short branches.—Fifteen species in N. Amer., Eu. and Asia, all mentioned below.

Numerous varieties are cultivated in Europe for their edible nuts. They are also valuable for planting shrubberies, and thrive in almost any soil. The foliage of some species turns bright yellow or red in autumn. Propagated by seeds sown in fall, or stratified and sown in spring; the varieties usually by suckers, or by layers, put down in fall or spring; they will be rooted the following fall. Budding in summer is sometimes practiced for growing standard trees, and grafting in spring in the greenhouse for scarce varieties. They may also be increased by cuttings of mature wood taken off in fall, kept during the winter in sand or moss m a cellar and planted in spring in a warm and sandy soil. Illustrated monograph of the cultivated varieties by Franz Goeschke, Die Haselnuss (1887). See, also, bulletin on Nut- culture by the U. S. Dept. of Agric. For the culture of the nuts, see articles Filberts and Hazels.

C. colchica, Alboff. Low shrub, to 3 ft.: lvs. ovate or obovate, densely doubly serrate, sparingly pilose: involucre connate, with a short lacerated beak, pubescent. Caucasus. Winkl. 53. Not in cult.—C. colurnoides, Schneid. (C. intermedia, Lodd., not Fingerh., C. Colurna X C. Avellana). Similar to C. Colurna: small tree or large shrub, bark darker: involucre shorter, scarcely glandular. Garden origin.—C. Fargesii, Schneid. (C. mandahurica var. Fargesii, Burkill). Tree to 45 ft.: lvs. narrow-obovate to oblong: involucre soft-pubescent, sometimes only slightly so. W. China.— C. Jacquemontii, Decne. (C. Colurna var. lacera, DC.). Allied to C. chinensis. Tree: lvs. ovate, lobed toward the apex, less pubescent, 5-8 in. long: involucre pubescent, not constricted, lobes not or rarely forked, often dentate. Himalayas. Alfred Rehder. CH

The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.



Pests and diseases


The species of hazel are grouped as follows:

Several hybrids exist, and can occur between species in different sections of the genus, e.g. Corylus x colurnoides (C. avellana x C. colurna).



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