Detailed Explanation of Key Techniques for Grafting Ginkgo Trees in Autumn
Ginkgo, a deciduous tree of the Ginkgo family and genus. Ginkgo appeared hundreds of millions of years ago and is the oldest relict plant among the gymnosperms left over after the Quaternary glaciation. The ginkgo trees still alive today are rare and scattered, and old trees over a hundred years old are no longer common. All other plants in the same class as it have become extinct, so ginkgo also has the reputation of being a living fossil. Varieties and cultivars include: yellow-leaf ginkgo, tower-shaped ginkgo, split-leaf ginkgo, weeping ginkgo, variegated-leaf ginkgo and others, 26 kinds in total. The fruit of the ginkgo tree is commonly known as white fruit, so ginkgo is also called the white fruit tree. The ginkgo tree grows slowly and has an extremely long lifespan. Under natural conditions, it takes more than twenty years from planting to bearing ginkgo fruit, and only after forty years can it bear fruit in quantity, so some people also call it the “grandfather-and-grandson tree”, with the meaning that “the grandfather plants it and the grandson gets to eat”. It is the long-lived elder among trees and has ornamental, economic and medicinal value.
Geographical distribution of ginkgo
Ginkgo first appeared 345 million years ago in the Carboniferous period. It was once widely distributed in Europe, Asia and the Americas in the Northern Hemisphere. In the Mesozoic Jurassic period, ginkgo was widely distributed across the Northern Hemisphere, and it began to decline in the late Cretaceous. By 500,000 years ago, it had become extinct in most of Europe, North America and Asia, and only the populations in China survived. Ginkgo distribution mostly belongs to areas of artificial cultivation, with large-scale cultivation mainly in China, France and the state of South Carolina in the United States. There is no doubt that ginkgo abroad was introduced directly or indirectly from China.
Ginkgo is widely distributed in large amounts in countries and regions such as China, Japan, Korea, South Korea, Canada, New Zealand, Australia, the United States, France and Russia. The natural geographical distribution range of ginkgo is very broad. From the perspective of horizontal natural distribution, ginkgo near the 30° north latitude line has the longest east-west distribution distance. In China, the cultivation area of ginkgo is very wide, mainly distributed in temperate and subtropical climate zones, spanning 21°30′~41°46′ north latitude and 97°~125° east longitude, covering 22 provinces (autonomous regions) and 3 municipalities directly under the central government. From the eastern plains at an elevation of several meters to several tens of meters to the mountainous areas of the southwest at around 3000 m, well-growing ancient ginkgo trees have been found. In terms of resource distribution volume, Shandong, Zhejiang, Jiangxi, Anhui, Guangxi, Hubei, Sichuan, Jiangsu, Guizhou and other provinces have the most.
Techniques for grafting ginkgo trees in autumn
Autumn grafting time
Autumn grafting of ginkgo is best done from mid-August to mid-to-late September, and the specific time can be flexibly controlled in different places according to different climates. Selection of scions
Local superior ginkgo tree varieties that have already begun to bear fruit should be selected as mother trees for collecting scions, and collection should be done when the new shoots stop growing and the branches have become lignified. The scions cut should be well-developed current-year new shoots. To prevent the scions from losing water, the leaves should be removed immediately after cutting. If the bud grafting method is used, the leaf stalks should be retained when removing the leaves; if the branch grafting method is used, the leaf stalks should not be retained. It is best to collect, transport and graft the branches as you go. When grafting in the field, they should be placed in a basin or wooden bucket with a little water, covered with a wet cloth, and taken as grafting proceeds. Grafting methods
Autumn grafting of ginkgo mainly uses the cleft grafting method or the whip-and-tongue grafting method. In the cleft grafting method, the height at which the rootstock is cut should be determined according to the length of the scion; generally the retained rootstock height is 2 times the length of the scion. The scion may retain 3-4 buds. Use a knife to make a vertical split in the center of the rootstock cut, with the depth depending on the thickness of the scion, deeper for thick and shallower for thin. Cut the lower end of the scion on both sides to form a wedge shape. The wood layer between the two cut surfaces should be slightly thicker on one side and slightly thinner on the other, and the cut surfaces should be flat and smooth. Then insert the scion into the split in the rootstock so that the cambium of the rootstock and the scion fit closely together, and finally tie it tightly with binding material. In the whip-and-tongue grafting method, the scion length and the retained rootstock height are the same as in the cleft grafting method. The diameters of the rootstock and scion are best equal; if they are not equal, the scion diameter should be smaller than the rootstock diameter. Cut a 3 cm-4 cm long slanted surface on each of the scion and rootstock, then make a straight cut of 1 cm-2 cm at 2/3 of each slanted surface to form a tongue shape, and insert them into each other. If the scion and rootstock are the same thickness, align the cambium on both sides; if the rootstock is slightly thicker, they can be aligned on one side, and finally bind them. Management after grafting
Temperatures are relatively high during autumn grafting. As long as suitable humidity is maintained and management measures such as weeding and fertilizing are carried out in time, the graft union can heal quickly, and the scion may also sprout. However, the binding can only be removed after sprouting in the following spring.