There are about 20 species in the world, and there are 12 species in China. The main species are Corylus heterophylla, Corylus pubescens, Corylus heterophylla, Corylus spinosa and Corylus yunnanensis.
Corylus heterophylla is a tufted shrub with a height of1.5 ~ 2.0m; Unisexual flowers, monoecious; Male flowers are inflorescences, often 2 ~ 9 flowers are inserted in the leaf axils of the middle and upper parts of new shoots; The female flower is inserted near the male inflorescence, with two bright red stigmas, and the bud top is exposed when it opens; Nuts, 1 ~ 4 clusters.
The roots of Corylus heterophylla can generate underground rhizomes in the soil, which are staggered and easy to germinate new clumps. Each cluster of rhizomes can be as long as 1 ~ 2 meters and 2 ~ 4 cm in thickness. Because the roots spread deeply in the topsoil and tillers, hazelnuts can naturally grow.
Hazelnut branches can be divided into growth branches, fruiting mother branches and fruiting branches. Branches without flower buds extracted from leaf buds or hidden buds at the base of plant clusters are growth branches; There are male inflorescences and flower buds as the fruiting mother branches; After the mixed bud germinates, the bright red stigma is exposed from the top of the bud, and then a short branch with leaves is born, which is the fruiting branch, also called the fruiting new shoot.
When the hazel tree is sown, the underground root system grows vigorously at first, and the aboveground part grows slowly, and it begins to bear fruit after 3 ~ 4 years. For example, after stubble leveling, the fruiting mother branches of male inflorescences or mixed flower buds can sprout about 1 m per year, and a large number of fruiting branches will be produced in the second year, and the fruiting intensity will gradually decrease after the fifth year. Therefore, after the completion of hazelnut orchard, it is necessary to renew the stubble every certain number of years to promote its growth, fruit and rejuvenation. It is more suitable to level stubble in late autumn or winter after defoliation. At this time, the organic nutrients produced by leaves and branches have been transported to the roots for storage, and less nutrients are lost after stubble cleaning, which is beneficial to the growth of the next year; According to the growth and fruiting characteristics of Corylus heterophylla, the basal branches that occurred after stubble regeneration 1 year generally could not bear female flowers, but only male inflorescences. However, under good nutritional conditions, mixed buds can also be formed in the middle and upper parts of the base branches in the same year, becoming the fruiting mother branches, and the new shoots will blossom and bear fruit in the next year. However, it is not easy to form mixed buds because a lot of nutrients are consumed after fruiting. So the fruit yield in the third year is often very small, and it can be very high in the fourth year. Later, with the increase of clump age, the growth gradually weakened, and it began to age in the 5 th to 6 th year, and the yield decreased. Therefore, the interval of stubble leveling in hazelnut orchard should be every 4 ~ 5 years 1 time. In order to make the hazelnut orchard of 4-5 years old get higher yield, it can be divided into 4-5 pieces according to the size of hazelnut orchard, and stubble 1 piece can be left every year to ensure a certain yield every year. When leveling stubble, you must have a sharp knife, cut it into horseshoe shape at 3 ~ 5 cm from the ground, and the stubble should be smooth to facilitate the emergence of new branches.
At present, many hazelnut orchards are semi-wild, with extensive management, lack of fertilizer and water, low yield and serious fruit hanging every other year. If we can strengthen the management of fertilizer and water, and then adjust it reasonably, we can not only improve the yield, but also promote the differentiation of flower buds, eliminate or alleviate the phenomenon of combining every other year, and maintain normal fruit and high yield year after year.