Hazelnut, belongs to the family Corylus
, which includes C. avellana
(Common or European hazelnut) and the closely related species C. maxima
(filbert). Hazels are deciduous trees or shrubs in the family Betulaceae grown for their edible nuts. Hazelnuts are large multi-stemmed shrubs or small trees with rounded leaves which possess a doubly serrated margin (each tooth bears another tooth). They produces flowers very late in the winter prior to the emergence of any leaves. The female flowers are small and only the bright red stigmas are visible protruding from the bud. The male flower is a catkin which is pale yellow in color and measures 6–12 cn (2–5 in) in length. The fruit of the hazelnut is a classic nut which grows in clusters of 1–5, each protected by a leafy husk which covers most (common) or all of the nut (filbert). The nut is oval in shape and yellow to brown in colour. Each has a pale scale at its base. When ripe, the nut falls from the husk to the ground. Hazenut can reach a height of 3–8 m (10–26 ft) and can live for many years, although its commercial lifespan is usually about 40 years. Hazelnut originates from Europe and South East Asia.
Young hazelnut trees
Hazelnuts on the tree
The kernel of the hazelnut is edible and can be eaten raw or toasted. The kernels can be processed to produce praline or as an ingredient in confectionery and baked goods.
Filberts are hardy plants which can survive adverse growing conditions. They should be grown in a soil which is at least 2.4 to 3 m (8-10 ft) deep and will grow optimally in well-draining, fertile loams with a pH between 5.5 and 7.5 in full sun or partial shade. Filberts will grow well in areas where wild hazel grows large and vigorous.
While it is possible to propagate filberts from cuttings, the success rate for obtaining rooted cuttings is usually only between 20 and 50%. The most successful method of propagating filberts is by layering. The most successful and widely used method of layering for commercial filbert production is tip layering. Tip layering involves bending shoots into a V-shape and burying the lower parts in the soil to a depth of 20 to 25 cm (8-10 in) while the tips of the shoot, which will form the new tree tops, are kept upright. The soil is kept moist to promote root development above the V bend on the tip and roots should ideally be congregated in a 5 to 10 cm (2-4 in) section of the shoot.
Trees should be planted in early winter while dormant. The trees should be planted at least 6 m (20 ft) apart. Before planting, remove as much as possible of the old layered shoot and prune back the ends of any broken roots. Plant the tree in a hole large enough to accommodate the roots but avoid deep planting. Fill in the hole around the roots with fine soil, pressing down with your hands to eliminate any air pockets around the roots. Add soil on top of the roots and tamp down to set the tree. Fill in the remainder of the hole with loosely packed soil. Once planted, the tree should be headed back in order to compensate for reduced water uptake. the tree should be cut back to a height of 45 to 76 cm (18-30 in).
Hazelnut trees produce suckers which should be removed from the tree at, or close to, their point of origin on the trunk. This can be achieved by gently removing the soil from around the sucker. While the trunk is exposed, any other buds which are beginning to show should also be removed. Cutting the sucker at or just below the soil line will encourage more suckers so it is important to make the cut as close to the trunk as possible.
Newly planted trees usually bear nuts within two to three years after planting although full production may not be reached until twenty five years after planting. The nuts are usually harvested two to three times over the season. The nuts can be spread out on the ground to dry or, as with commercially produced nuts, dried artificially at a temperature of 90 to 100°C (176-212°F).
Beddes, T., Renquist, S., Kuhns, M. & Pace, M. (2011). Hazelnuts in the Home Orchard. Utah State University Cooperative Extension. Available at: http://extension.usu.edu/files/publications/publication/Horticulture_Fruit_2011-01pr.pdf. [Accessed 17 December 14]. Free to access
Schuster, C. E. (1937). Filberts. Oregon State System of Higher Education Federal Coperative Extension Service. Available at: http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/17152/Extensionbulletin503.pdf?sequence=1. [Accessed 17 December 14]. Free to access
Teviotdale, B. L., Michailides, T. J. & Pscheidt, J. W. (eds) (2002). Compendium of Nut Crop Diseases in Temperate Zones. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopapspress/Pages/42848.aspx. Available for purchase from APS Press
Common Pests and Diseases
Category : Fungal
Armillaria root rot (Oak root fungus)
Small, discolored leaves which drop early; death of branches; death of plant; clusters of honey-colored mushrooms may sprout at base of plant
Armillaria root rot cannot be effectively controlled once it has become established in an orchard; diseased or dead plants should be uprooted and removed; planting resistant rootstocks is the most effective method of preventing the disease
Eastern filbert blight
Initial symptom of disease is the presence of cankers, usually on branches near the top of the tree; blossoms; cankers can appear subsequently on any part of the plant causing leaves to rapidly wilt and dieback of branches
Prune out branches and twigs with cankers where possible; cuts should be made 0.6 to 0.9 m below the canker; pruning waste should be destroyed; destroy any volunteer hazelnut trees from abandoned orchards
Small powdery white patches on leaves and fruit which can expand to cover the entire leaf or fruit surface; small black fungal fruiting bodies are often visible in the white patches
Disease does not cause severe damage to hazelnut and control is not warranted
Category : Bacterial
Dieback of young twigs and branches; necrosis of buds and twigs; small, angular or round water-soaked which turn red-brown in color; stems may be girdled by cankers and leaves are killed but remain attached to the tree
Diseased areas of tree should be pruned out by making cuts 0.6 to 0.9 m below the diseased area; avoid planting hazelnut in water-logged or poorly draining soils; providing trees with irrigation to reduce water stress for the first 3 years after planting can greatly reduce mortality; applications of copper-based bactericide is recommended to control the disease
Buds fail to break in Spring and new growth is withered and dying; leaves become chlorotic and die; dead leaves remain attached to the tree after leaves drop from the tree in Fall; if infection begins at the base of the tree, cankers are formed in the bark and are visible as light gray areas
Plant only certified, disease-free nursery stock; prune out infected stems; applications of copper-based chemicals such as Bordeaux mixture during leaf drop can help to control the disease
Category : Viral
Apple mosaic virus (ApMV)
Yellowing of leaves which may occur as rings, lines, flecks or vein banding; young hazelnut trees may exhibit a reduction in new growth and reduced yield if disease occurs in conjunction with other viruses; infected plants may have no outward symptoms
Only plant trees derived from virus-free stock; there is no known resistance to the virus