Speed-up cultivation method for big tree based on approach grafting of single saplings

The invention discloses a speed-up cultivation method for a big tree based on approach grafting of single saplings. According to the invention, by adopting a speed-up cultivation technology based on approach grafting of the single saplings through simultaneous development and aggregative adherence, a famous and valuable landscape tree with an age of 3 to 5 years has ornamental properties and practicability of a native tree with an age of 50 to 300 years, so engineering requirements are reached; and a tree (with a height of 15 centimeters, 20 centimeters, 25 centimeters, 30 centimeters, etc.) capable of reaching the requirements of engineering seedlings can be custom-cultivated according to the engineering requirements, wherein the trunk of the tree is straight from top to bottom; the shape of the tree is beautiful; and flowers of the tree are colorful. The cultivation method provided by the invention shortens the growth cycle of a tree seedling, and has milestone and intergenerational significances in the dev