Grafting is a technique that allows you to combine a cutting from one tree with the rootstock of another. This can be useful to continue to get a reliable crop of a particular cultivar – for instance, the seed from certain types of apple trees will not go on to be copies of the parent tree so grafting allow you to reproduce from the original cultivar – but also allows you to continue to utilize a vigorous rootstock even when the tree may have lost its production value, and to combine species to produce hybrid fruit. Grafting is also useful as a way of repairing trees that may have been damaged by climatic events such as strong winds or disease, allowing you to replace dead branches that have had to be removed with young, living stems. There are several different methods for grafting fruit trees.
The whip method of grafting needs the branch to which the graft will be attached and the appendage – called the scion – to be roughly the same size and diameter to work effectively. The branches also need to be quite slender, no more than half an inch across as there is less support for the graft than in other methods. This is why the technique is often used on young apple and pear trees to produce hybrids, rather than on older rootstock. The end of both the branch and the scion are cut at an angle, quite shallow to expose as much surface area as possible, and then the two cut sides are placed face to face. The join is then bound with electrical tape to protect the graft and prevent water and disease entering the wound.
The cleft technique of grafting is used to bring vitality back to older, less productive trees whose rootstock remains strong. It is used primarily on apple and pear trees, and can be utilized on the trunks of small trees or the main branches of larger trees. Ideally, you want to use this technique on branches or trunks between two and three inches in diameter, and should not be more than a few feet from the ground or the new tree may grow too large and prove difficult to harvest. Cut off the trunk or the branch with a saw, and then use a hatchet or sharp knife to cut a cleft in the exposed end of the tree limb. Cut the end of the scion into a wedge shape and insert into the cleft. You should not need to cover the graft if the union is tight and secure.
Side grafting sits somewhere between whip and cleft grafts. It is used on trees that are too old for whip grafting but too young and viable to be cut back for bark grafting. Rather than grafting into the cut end of a removed branch, you graft the scion into a cut made into the side of the branch. The cut should be made on a branch at least a foot away from the trunk and should extend no more than halfway across the diameter of the branch. Use a sharp knife rather than a hatchet to retain control over the cut. As above, fashion the end of the scion into a wedge and insert into the cut. If required secure with twine until the graft has taken.
Bark grafting is typically – like the cleft method – used when an old tree has lost its fruiting vigor. The rootstock is still likely to be robust, however, and grafting young plants onto it can revitalize the tree. It involves sawing off the majority of the tree that is above the ground. You want to take it back to around knee height. Then you use a sharp implement inserted between the bark and the tree on the remaining stump to gently ease the bark away from the underlying wood, creating a gap. The scion – prepared as with the other methods, to have a wedge shape at the end to be inserted – is inserted into this gap, and then the bark is bound tightly to the scion by wrapping either twine or electrical tape around the tree. You may wish to insert two or three scions into the bark and cut back to one when you have determined which has established itself the best on the rootstock. Once a graft has taken, remove the tape or twine so that the tree can grow naturally. Try not to cut the tree back until you are ready to graft – late winter or early spring are the best times for bark grafting – as water can easily get into the tree and potentially spread disease.
In all the instances above, make sure that the scion you use for the graft has buds on it, as these are essential for fruit forming. Three buds are generally considered a good number for a grafted scion, so that the graft will not depend upon the success of just one. In most cases the best time to graft is in the spring, usually around April or May, when the buds of the scions have set but they have not yet blossomed. There is ne form of grafting that is slightly different.
As the name suggests, this form of grafting focuses on the bud. In fact, it uses just a single bud as the scion, rather than a length of stem or branch. It is often used for fruit trees such as cherry, apricot and plum, which are less amenable to whip and cleft grafting methods. And because you want to use a well-grown bud, it is done in the summer, when the buds have fully developed, rather than the spring. This is also when the bark of the tree to which you are grafting the bud will be at its most pliable. Cut off the bud, leaving about half an inch of stem to hold it by. Cut off any leaves around the bud. Use a knife to cut a ‘T’ shape cut into the bark of the branch you want to graft to, making sure it is at least fifteen inches from the trunk. Slide the ‘handle’ of the bud into the cut and then secure with electrical tape, making sure you leave the bud exposed.