Grafting is a form of propagating new fruit trees using buds or twigs – the ‘scion wood’ from an existing tree and fusing it onto a branch or stem of another tree – ‘the rootstock’, which is selected for size, suitability to site and tolerance of certain soil conditions.
Once you have got the hang of it, you can look forward to getting new trees for a fraction of what you would pay down at the nursery.
Grafting produces clones of known fruit varieties. This technique is thousands of years old and is the only way to guarantee that the fruit grown on a new tree is the variety we want. Simply planting the seeds of our favourite fruit will produce new varieties with unknown qualities.
There are two main techniques for grafting fruit trees – whip grafting, where a short piece of scion wood is attached to the rootstock in late winter/early spring, producing a single stem one-year old tree by the following summer. Bud grafting occurs where a single bud is attached to an actively growing rootstock in summer time. Whip grafting allows the tree to develop more quickly because it uses a larger piece of the scion wood however bud grafting produces a straighter tree and a stronger union.
Whip grafting is often done inside with dormant rootstock dug out of the ground. This is called bench-grafting. An alternative method, used where there is sufficient land available is field grafting, where the rootstock is left undisturbed in the ground and the grafting is done there and then.
Selecting Scion Wood
Choose a healthy tree if possible, use well ripened, mature green wood from the outside/sunny side of the tree (interior wood may be ‘etiolated’ – pale and weaker).
Cut a 3-4cm whip with three buds present:
- Stock bud: just behind the grafting cut, helps with callusing
- Top bud: to form the shoot
- Middle bud: back-up if the top bud fails
Attaching the Scion to the Rootstock
Cut back the rootstock to between 15-30cm – too low a graft union invites pathogen risk from splash back from the soil. Too high, especially on dwarfing rootstock can make for a weak union.
The ends of each joining piece should be cut in matching clean elliptical slices so that when joined together, as much of the cambium layer (the part of the wood between the outer bark and the woody bit) as possible is touching. This may take some practice!
Leave a small ‘church window’ of internal scion wood sticking over the top of the rootstock wood to help with callusing.
Putting horticultural wax on the open cuts will help prevent water loss.
For bud grafting, look for a plump, healthy looking bud from the outside/sunny side of the tree that is not dry and shrivelled or with obvious damage to create your scion.
Using a grafting knife, cut a small slit into the bark ½ an inch underneath the bud and slowly pull the knife upwards taking in the cambium layer and outer bark without cutting into the heartwood, or inner part of the branch. End the slice ½ an inch above the bud, so it comes away neatly.
Cut a 1 inch vertical slit into the branch where the bud will be placed, cutting only into the bark layer. At the top of this incision, cut a cross-wise slit, creating a T-shape.
Then, gently lifting the corners where they meet, slide in the scion bud with the growing tip pointing upwards, ensuring that the cambium layers on each are touching.
Wrap the join in grafting tape to keep dry and in the following spring prune off the tip of the branch as soon as the grafted bud begins to grow.
Further reading – The Grafter’s Handbook by R.J. Garner