Ficus Techniques : 58

Thread Grafting Ficus, or Almost Anything Else

by Iris Cohen

Some fig species are very generous at budding back on the trunk. Others are reluctant, or only oblige on a hit-or-miss basis. Many Ficus pre-bonsai are sold with the canopy arranged at the top of a long and bare trunk. This lack of branching is especially awkward with the mass-produced Tiger Bark and other figs sold with S-curves in the lower trunk.

A curve or lump in the trunk usually begs for a branch at that point. Sometimes a fig can be persuaded to bud back on the lower trunk by shortening the top and severely pruning or removing all the existing branches. However, to get a branch to grow at a particular point requires grafting. The easiest grafting technique to learn is thread grafting. Several tutorials with diagrams can be found on the internet, such as one at Bonsai4Me, Colin Lewis, Jerry Meislik and others also have details in their books.

I have successfully thread-grafted crabapple, maples, and Tiger Bark fig, Ficus microcarpa. With tropical species, especially growing in the North, the speed at which grafts take may depend on the season. There is no hurry. Just leave the graft on as long as necessary. Meanwhile, keep the feeding part of the donor branch trimmed (the part coming to the trunk}. You want as much energy as possible to go into the grafted part of the branch.

The first step in thread grafting is to encourage a thin branch that is long enough to go through the trunk and come out the other side at least an inch or two (three to five centimeters). Just before the operation, trim the side branches and cut off the leaves from the part that will be put through the trunk and grafted. If the branch is stiff, wire it so it will stay in place and not pull back out. If the branch has bark where it will go through the trunk, scrape some off and expose the green layer. This is not necessary if the branch is still green or has only a thin skin.

Mark the trunk where you want the branch to emerge. If at all possible, drill from that side. Start the hole with an awl so the drill will not wander. Have the branch emerge from the trunk following the branch angle pattern consistent with your design. If it is on the lower part of the trunk, it should normally angle down slightly, so you will drill slightly upward. Start with a drill bit a little smaller than you might need, then increase the size until the branch just goes through. Push it through gently until it comes out as far as possible.

Seal both ends of the graft at the junction with the trunk with cut paste or grafting wax. In addition, I always bandage it with a figure-eight bandage of florist’s tape. By the time the tape comes off, you probably no longer need it. Leave the cut paste on until it dries up; normally a couple of months. Feed the tree generously and keep the other branches trimmed, so the strength will go into the new branch.

There is one simple test to know when it is time to sever the donor branch. The part of the new branch emerging from the trunk will be thicker than the part going in. This shows that the cambium layers have merged. Cut the donor side off at the trunk and style the branch with the rest of the tree. There may be a small scar at the back of the graft, but that will fade. The new branch may be brittle for another year. Wire it very carefully.


Ficus microcarpa with two grafts

Closer view of grafts

My own Tigerbark fig with cut paste on left grafted branch.

Fig with graft close-up

Red line shows one branch, blue line a second graft, newly placed - green florist tape around the graft points


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