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Grafting is a method of plant propagation widely used in horticulture (gardening), where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially. (Grafting is limited to dicots and gymnosperms. Monocots lack the vascular cambium required.)
In stem grafting, a common grafting method, a shoot of a selected, desired plant cultivar is grafted onto the stock of another type. In another common form called budding, a dormant side bud is grafted on the stem of another stock plant, and when it has fused successfully, it is encouraged to grow by cutting out the stem above the new bud.
For successful grafting to take place, the vascular cambium tissues of the stock and scion plants must be placed in contact with each other. Both tissues must be kept alive until the graft has taken, usually a period of a few weeks. Successful grafting only requires that a vascular connection takes place between the two tissues. A physical weak point often still occurs at the graft, because the structural tissue of the two distinct plants, such as wood may not fuse.
Additional recommended knowledge
Reasons for grafting
The easiest and most common form of grafting is cleft grafting. The stock is simply split and the scion is inserted. It is best if the stock is 2-7 cm in diameter and has 3-5 buds, and the cleft is around 7cm deep. The scion is cut in a wedge shape and inserted into the tree with the cambium. The bare stock is covered with grafting compound, otherwise the cambium layer quickly dries and the graft fails.
Stub grafting is a technique that requires less stock than cleft grafting, and retains the shape of a tree. Also scions are generally of 6-8 buds in this process.
An incision is made into the branch one centimeter above, then the scion is wedged and forced into the branch. The scion should be at an angle of at most 35° to the parent tree so that the crotch remains strong. The graft is covered with grafting compound.
Awl grafting takes the least resources and the least time, but the most skill. There is a danger of accidentally driving the tool too far into the stock, lessening the scion's chance of survival. Awl grafting can be done by using a screwdriver to make a slit or T-shaped incision in the bark just so far as the cambium layer. Then the shield or wedged-shaped scion is inserted into the incision. Awl grafting is commonly used to graft buds.
Veneer grafting, or inlay grafting, is a method used for stocks larger than three centimeters in diameter. The scion is recommended to be about as thick as a pencil. Clefts are made of the same size as the scion on the side of the branch, not on top. The scion end is shaped as a wedge, inserted, and wrapped with tape to the scaffolding branches to give it more strength.
"Renewing fusion" is a grafting method in which a small branch (at least a centimeter wide) from one plant to a main branch of another, by carefully shaving a proper amount of bark from the large branch and inserting the scion into a cut hole. The graft is taped with a thin strip of duct tape in diagonal lashings, to hold it up and to prevent insects from entering the hole.
The tree roots of the same species will sometimes naturally graft where they make physical contact with each other. A group of trees can share water and mineral nutrients via root grafts, which may be advantageous to weaker trees. A problem with root grafts is that they allow transmission of certain pathogens, such as Dutch elm disease. Natural grafting also sometimes occurs where two stems on the same tree, shrub or vine make contact with each other. This is most common in plants such as strawberries and potatoes.
Grafting has been important in flowering research. Leaves or shoots from plants induced to flower can be grafted onto uninduced plants and transmit a floral stimulus that induces them to flower.
The transmission of plant viruses has been studied using grafting. Virus indexing involves grafting a symptomless plant that is suspected of carrying a virus onto an indicator plant that is very susceptible to the virus so shows symptoms quickly.
Grafting is often done for non-woody plants such as a tomato, cucumber, eggplant and watermelon. The main advantage of grafting is for disease-resistant rootstocks. In Japan there is an automated process using grafting robots.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Grafting". A list of authors is available in Wikipedia.|