Family: CORYLACEAE
The hazelnut is a small tree growing to a height of about 5 m, with a spread of about 5 m. The main variety grown commercially is the European hazelnut (Corylus avellana), although the Mediterranean hazelnut (Corylus maxima), also known as the filbert, has provided the basis for many varieties and crosses. In the USA all varieties of hazelnut are known as filberts, but in Europe those varieties where the husk is longer than the nut, are known as filberts, whereas varieties having husks shorter than the nut are known as cob varieties.
The hazelnut will begin bearing nuts at about 4 years of age, and can be expected to live for about 50 years. It does not often yield a heavy crop of nuts in Western Australia, as it has a high chilling requirement and the winters are generally not cold enough. The chilling requirement varies from 800 to 1600 hours at temperatures less than 7°C, depending on varieties. The flowers will however, survive at temperatures as low as - 20oC. In Victoria, yields of hazelnuts have been recorded from 0.28 kg/tree at 3 years of age, to 6.6 kg/tree at 11 years of age, with a potential to produce up to 20 - 25 kg/tree at full maturity.
Because the male flowers (catkins) produce pollen before the female (pistillate) flowers on the same tree are receptive, hazelnuts need a polliniser of a different variety, which will produce pollen at the appropriate time. The nuts will begin to appear in late spring and most of them will reach full size by the end of December. By the middle of February the nuts should be fully ripe.
Hazelnuts grow best in deep, well - drained, loamy soil and require little added fertiliser. In dry areas, irrigation is required for good nut production. A neutral pH is preferred. The recom-mended planting distance is about 5 m, although they can be grown as an understorey to larger species of orchard trees. The hazelnuts can also be intercropped with strawberries or other berries, vegetables or flowers. Alternatively, a green manure crop could be grown.
If the hazelnut is grown as a shrub, little pruning is required, although for optimum yields it is desirable to remove most of the suckers. If it is grown as a tree, the suckers and some branches will need to be removed. It is best trained as a central leader, that is, all side limbs growing from a main trunk. Pruning both the tree and shrub forms should be aimed at increasing the amount of light reaching the centre of the tree and to maximise the amount of one - year old fruiting wood. Old or weakened trees can be rejuvenated by cutting back to the soil surface and allow-ing new suckers to regenerate.
Propagation can either be from seed, sucker or by layering. When growing from seed, stratifica-tion is necessary for a period of 60 - 100 days, depending on variety. Seedlings however, seldom retain the characteristics of the parent tree.
Nuts should be harvested as they fall from the tree, being gathered as often as possible. They can be sun - dried and stored in the shell for many months in a cool place. The shelled kernels will keep for several weeks at room temperature.
Nutritional composition of the hazelnut per 100 grams of edible portion is: Water - 5.4%, Energy - 634 calories, Carbohydrate - 16.7 g, Fat - 62.4 g, Protein - 12.6 g, Ash - 2.5 g, Calcium - 209 mg, Potassium - 704 mg, Sodium - 2 mg, Magnesium - 184 mg, Iron - 3.4 mg, Phospho-rous - 337 mg, Chlorine - 60 mg, Sulphur - 446 mg, Iodine - 0.002 mg, Thiamin - 0.46 mg, Niacin - 0.9 mg. and the digestion time is 3 hours.
When coppiced, the young wood is used for sheep hurdles, cask hoops, crates and walking sticks. The wood also yields good charcoal. The leaves have potential for animal fodder.