Grafting not only allows us to select the particular characteristics of the top part of the tree (so that we have the fruit we desire), but it also allows us to select the most appropriate rooting system (to control the vigour of the tree, or for resistance to root diseases, etc). The best grafting wood (scion wood) is usually one-year wood, and success rates are lower for older wood. It should be gathered during winter when it is dormant, and stored in a plastic bag in the fridge so that it doesn't dry out, go mouldy or break dormancy before you need it. The best time to graft it onto a rootstock is usually in the spring when the rootstock is corning out of dormancy.
Grafting normally needs to be on to a rootstock of the same genus to be successful, ie. apples onto apples, but there are a few exceptions.
There are a variety of grafting techniques, including Cleft, Whip & Tongue, and Chip Budding. The trick is to get the structures of the grafted wood properly aligned with the same structures of the rootstock. It is particularly important to align the cambium layer. Bind the union with grafting tape or similar, trim the scionwood back to just one or two buds, and apply wax or paint to the cut end to prevent drying out.
It is certainly worth learning and most of us find that with a little practice we can produce a passable graft, and it really didn't matter if it took us a little time to get it right. Speed can come later.
Some reasons for grafting
Seeds are genetically variable so do not produce offspring identical to the parent plant (just as human children will not be identical in all respects to their parent). Grafting allows us to choose what we get.
By choosing selected rootstocks we can choose the size the grafted tree will grow to. This is important for maximum production per hectare, for ease of harvesting the fruit and for smaller gardens.
Rootstocks can be chosen which are resistant to soil-borne rots and diseases.
It is possible to put a number of varieties on the same roots, which can save space in a small garden, give added interest and choice, and provide for good fruit-set through cross pollination.
In some tree species the individuals are either male or female, and grafting gives us a choice.
Rootstock (or understock) is the part of the tree with roots, onto which we graft the chosen top.
Scion (or scion-wood) is the chosen top. Usually it must be the same sort of plant as the rootstock i.e. graft apples to apples, pears to pears, etc.
Cambium is the layer of growing tissue which occurs between the woody part of a stem and its bark. Because this is the place where growth takes place it is important during grafting to line up the cambium layer of the scion with the cambium layer of the rootstock, so that they can grow together.
Compatible is the term used to describe plants which, when grafted together, form a good, sound, permanent union.
This article is reproduced with the kind permission of the New Zealand Tree Crops Association. For more information on useful tree crops - including nut and fruit trees, trees for shelter, timber, stock fodder and firewood - contact your local branch.