Origin and distribution
Carya cathayensis originated in China. As early as 40 million to 25 million years ago, Carya cathayensis was distributed in East China in the Neogene Oligocene. By Miocene, Carya cathayensis had become the main tree species of subtropical deciduous and evergreen broad-leaved mixed forests in this area. Later, under the influence of Quaternary glaciers, Carya cathayensis was destroyed in most areas. However, due to the mild offshore climate and complex terrain, the Carya cathayensis was not destroyed by the glaciers in the northern mainland, so that it was preserved and became one of the remaining tree species. Carya cathayensis is mainly distributed in Lin 'an, Chun 'an, Anji, Tonglu in Zhejiang and Ningguo, Shexian, Jixi, Jingde and other counties in Anhui, and most of them are native to Shan Ye or cultivated as trees.
Features and characteristics
The hickory tree is 30 meters high and has a trunk diameter of 30 ~ 66 cm. The bark is smooth and gray. Naked bud. Odd pinnate compound leaves with 5 ~ 7 leaflets. Monoecious flowers; 3 male inflorescences in a bunch; Female spikes are erect with1~ 3 female flowers. Nut has a four-sided involucre with obvious pinnate process. The surfaces of bare buds, leaf backs, shoots and involucres are densely covered with rusty yellow gland scales. Nuts are obovate or elliptic-ovoid, with small fruit shape and nucleolus as the main edible part.
Carya cathayensis has strong taproots, and the root distribution often exceeds1~ 2 times of the crown radius. Seedling trees begin to bear fruit in 7 ~13 years, and the economic life is generally as long as 25 ~ 50 years. The yield per plant is generally15 ~ 25 kg, and the highest yield can reach more than 50 kg. The buds on the new shoots are all naked buds, and the flower buds and leaf buds are not easy to distinguish. The naked buds germinate and branch in the next year. There are three types of flowering branches: female flowering branches, male flowering branches and mixed branches of male and female flowers. In the year of fruiting, bare shoots with short branches are often sprouted in the axils of1~ 3 leaves below the ear, and the branches grow for one year in the next year, and then the fruiting branches are sprouted on them in the third year. If the nutritional conditions are good, some buds can still sprout fruiting branches in the next year. New shoots are often concentrated at the ends of branches, and the middle and lower parts of branches are bare, so the resulting parts often move to the periphery of the crown, and the inner cavity and the lower part are empty. However, the hidden buds at the base of branches have a long life and often germinate into new shoots, so they are easy to be updated. It takes 120 days from flowering to fruit ripening, and the growth period is as long as 250 days.
Carya cathayensis likes warm and humid climate. The average annual temperature in its producing area is15 ~17℃, the annual precipitation is1000 ~1500mm, and the average temperature in July is 20 ~ 30℃. Carya cathayensis is a semi-positive plant, especially in the young tree period. In summer, direct sunlight will lead to growth retardation, scorched leaves and even death, so shade is needed. It is suitable for calcareous gravelly loam with deep and relaxed soil layer and high humus content, with a pH value of 6 ~ 7, and is most suitable for cultivation on sunny slopes with moist foothills or valleys and sheltered from the wind.
Main types and varieties
There are 20 species of Carya, most of which are native to America. There are 4 species native to China, among which Carya cathayensis is the best fruit quality. The newly discovered Carya cathayensis sa-rg. var. dabieshanensis y.z. hsu et n.c. tao-nov. Comb. is a variety of this species, distributed in Jinzhai County, Anhui Province and Moshan County, Hubei Province, with good fruit quality.
Carya cathayensis is propagated by seedlings in the producing area, and there are no definite varieties. There is little variation in nut shape, with an average weight of 4.2 grams. Two types have been identified: ① round fruit species. That is, common pecans, and most pecans belong to this type. The nut tip is oval, with a longitudinal diameter of 2.43 cm, a transverse diameter of 2. 10 cm and a thickness of 1.94 cm. The top of the nut is sharp, the base is round, the shell is thick (0. 1 1 cm), and the inner wall has two big partitions and six small partitions, so it is easy to peel. ② Flat fruit species. This type is in the minority. Nuts are oblate, with a longitudinal diameter of 2.05cm, a transverse diameter of 2.16cm, and a thickness of 2.09cm. The nuts are pointed, slightly protruding, with a thin shell (0.09-0.1cm), three partitions on the inner wall and nine partitions on the inner wall, so it is difficult to shell and the nucleolus is often incomplete.
Key points of cultivation techniques
Seedling propagation can be sown after seed collection. If the seeds are sown in the spring of next year, they should be stored in wet sand layer, and planted in seedbed in February, with the row spacing of 30cm×10cm, and shed for shade in summer. After two years of cultivation, it will be taken out of the nursery or used as rootstock. Grafting methods mostly use cutting or abdominal grafting, and the suitable time for branch grafting is from late March to early April. The garden should be built in the foothills with a slope below 25, and on the slopes above 10, terraces or fish scale pits should be built and planted, and the gentle slopes below 10 can be planted in trenches or level ridges with a row spacing of 6 meters. The plant spacing is 5 meters, and 330 plants are planted per hectare; For early high yield, the row spacing of 5m× 3m, with 660 plants per hectare, can also be used. When the canopy is connected and the light is affected, thinning will be carried out every other plant, which will be reduced to 330 plants per hectare. The garden can be intercropped with leguminous plants such as soybeans and peanuts or green manure crops within 5 years. In summer, shallow weeding or grass mulching should be carried out in the garden, and deep ploughing and fertilization should be carried out in winter, combined with renovation of terraces. Apply quick-acting fertilizer before spring germination, before flowering, during fruit development and after fruit picking, and add lime to acidic soil below pH 5.
In order to make the tree short and easy to manage, the top branches can be cut off when the tree is 7 ~ 8 meters high to promote the transverse development of the crown; The density of crown branches is too large, so it should be trimmed in time to make the crown ventilated and transparent; When the fruit of the old tree moves out, the big branches are retracted and pruned to promote the regeneration of the hidden buds at the base; Old and declining trees can be sawed off the upper part of the backbone branches and cultivated with new branches at the lower part, so that the trees can be rejuvenated and bear fruit continuously.
The main pests and diseases are root rot, plaster disease, wood rot, Carya cathayensis moth, giant salamander moth, small salamander moth, aphid, etc., which should be prevented in time.
Newly picked nuts, whose kernels are astringent, need to be boiled with water for about 4 hours and then taken out to dry before eating.
economic value
Carya cathayensis is one of the famous native products in Zhejiang. Stir-fried food is very crispy and sweet, and it is also the raw material of candy and cakes. Nutrilite is rich in nutrition, including protein 18.3%, and rich in carbohydrates and vitamins. The oil content is as high as 69.8 ~ 74.0%, and the oil can be 27 ~ 30 kg per 100 kg of nuts. The oil is of high quality and fragrant, and it is used for food or industry. Oil cake can be used as feed or fertilizer. The shell can be processed into activated carbon. Tannin can be extracted from fruit involucre. Wood can be used as excellent furniture and building and military materials.