There are a many good reasons to graft in relation to bonsai. Of course, it is one good method of propagating trees that may have desirable characteristics but weak roots on their own. But grafting can also be very useful for replacing undesirable foliage on a tree with excellent trunk characteristics, or for growing branches in areas that have none, or even for ramifying branches closer to the trunk. Trees with interesting nebaris or trunks, but with branches too high; collected trees with character but poor branching; and leggy trees with foliage only at the tips can all benefit from this technique.
Different grafting techniques are used depending on the purpose of the graft. This article will focus on bud-grafting Japanese black pines. This technique can be used for almost any grafting purpose on pines.
The tree itself must be healthy and vigorous. Trees should be repotted one year before they are grafted. Root pruning and the best possible care including heavy feeding will produce excellent new growth and enhance the vigor of the tree. This will provide excellent scion stock and speed the healing process.
Assembling all of your materials beforehand is essential. Once a scion has been trimmed, it must be inserted and covered immediately. You must be able to work efficiently and without hesitation. However, rushing can be dangerous to both the tree and your hands, so have everything close at hand and in its proper place.
New Zealand sphagnum moss (have some soaking!) retains moisture well and is easy to work with. All your tools must be as sharp as humanly possible. Besides a good sharp pair of shears, have your best and sharpest grafting knife at the ready, as well as an older knife, a narrow chisel, flexible plastic bags (be sure to split them on one side to facilitate placing them over the scion), and grafting tape or raffia to tie the bags over the graft.
Dull tools damage the live tissue in the areas you want to join. This makes it difficult for the graft to take. It’s also important for your own health. Dull tools slip at the most inopportune times, which can lead to fertilizing your tree with liquid blood meal! Therefore you will want your sharpening supplies nearby and ready so you can hone your good knife after every few cuts.
The Grafting Process
Step-by-step, here is the method for producing useful branches with bud grafts. Choose the buds you will use as scions the fall before you wish to graft. They should be strong terminal buds, so you must avoid pruning them by mistake. The buds must be healthy and dormant, so the awakening tree will also rouse them. If your buds are beginning to grow, they may need more nourishment than your tree is ready to give them, especially if you are grafting from one tree to another more dormant one. Also, the buds must have time to begin relying on the tree for growth. If they are too active, they will not have time to knit to the tree and will wither.
When grafting day arrives, first you will mark the spots on the tree where you desire a new branch to emerge. A Sharpie or even correction fluid will put a mark on the tree’s bark where you wish to work. Once you have your tree marked, remove the aged bark in those spots using your older knife. Pine bark is hard and resinous, and you do not want to dull the blade with which you will be trimming the scions.
Clean the bark from all your marks, and prepare your first scion. Some suggest cutting all your scions and laying them in front of you, to be trimmed as needed. I prefer to cut them as needed, to avoid letting them dry out. However, were I a professional with a thousand grafts to do, I might cut the scions in batches as suggested! I simply use my shears to cut a chosen bud with about 1 1/2″ of one year old wood below it.
Scion preparation continues as we remove all but a few of the needles on the scion. Remove all of them almost to the bud, leaving 4-5 pairs. Use your shears, as stripping them can damage the scion.
Now that the scion is prepared but not trimmed, it is time to cut the trunk in preparation for the graft. Using the chisel, insert the blade upward at your graft point at about a 30-35 degree angle. This produces a cut for a lower branch, which will need to be trained in a downward direction anyway. When grafting onto a branch or in the crown of a tree, make the cut so that the new branch faces in the natural position.
The end of the scion should be square. If it is angled, cut again so that the two cuts are intersecting properly. Otherwise, one side or the other will not match up to the stock. Making these cuts efficiently and quickly is crucial to the success of the process.
Immediately put wet sphagnum moss over the graft to retain moisture in the area. Then tie tightly with grafting tape. Leave the ends of the tape long so you can proceed with the next step. Place your bag over the scion, being careful to cover every needle, with the split side of the bag against the tree. Tie the top of the bag securely over the sphagnum, but make sure the moss does not extend outside the top of the bag, as it will wick moisture away from the graft and dry it out. (Editor’s note…a better method is to drop the sphagnum into the bag, then there are no worries about sealing the top tightly.)
Your graft is now complete.
Move the tree to a shady spot and keep an eye on the grafts. Water the tree normally, and be sure you see condensation on the inside of the bags. This will indicate that they are moist enough. Every two to three days you may need to moisten the moss. A hypodermic needle is ideal for this.
By May 31, the candle is obviously moving up, indicating that it has taken and is gaining sustenance from the trunk. It has only been about five weeks or so. Now it is important to make sure that the growing candle is not damaged by the bag, so it will be opened up.
Instead of removing the entire bag, I simply make a place for the candle to emerge and elongate. It will still benefit from the enhanced moisture inside the bag. Let this candle grow unimpeded for at least two seasons. The second graft hasn’t shown this kind of movement. A squirrel actually chewed a hole in the other bag, allowing it to dry out more. I am hoping with extra care, the second graft will take, too.
Grafting of all kinds is far less difficult than is supposed, and gives far more benefit than might be expected. Poor branching, leggy branches, and bare trunks can all be improved with grafting. One could suppose that there are trees in every private collection in North America that could be improved with good grafting technique. What about yours?
Just a couple of years had gone by when I snapped this shot of the grafted branch. Notice how well it has developed and how interior branching has grown. It’s a valuable part of the tree now.