Trunk-Fusion Project: A Progress Report

     One of our club activities last winter was a mini-workshop on trunk fusion. For any who don't know, this technique involves binding together some young and thin whips - however many you like - and forcing them to grow together to form a single thicker trunk. It's used primarily with vigorous, fast-growing species like trident maple (Acer buergeranum,) schefflera, and many species of Ficus.

For our mini-workshop, I used four rooted cuttings of Ficus microcarpa 'Tigerbark ,' of various thicknesses; the thickest was about the girth of a standard pencil. Some people use plastic wrap to bind the component trees together; I prefer zip ties. One bonsai master I know uses both, with the ties over the plastic. Whatever you use, the important properties of a binding material are, first, that it allow the bark to breathe; and, second, that it not stretch: the idea is to force the trunks together so they fuse.

The brown represents the trunks, the black the wire.

I enclosed something else within the bundle of trunks: a length of aluminum wire with a loop at one end, longer than all but the largest of the rooted cuttings. This sketch gives you the basic idea:

This is an experiment. The idea is that an anchor wire can be threaded thru the loop from below, and hold the tree in the pot without showing on the soil surface. It remains to be seen whether such a setup will adequately keep the tree from wobbling in the pot once its roots are re-established.

The upper length of the wire, starting from where it emerged from the bundle of trunks, was used to give some shape to the upper part of the primary trunk.

I meant for the wire to be in the center of the bundle, but the shapes of the trunks were such that it was forced to one side and partly exposed. However, given the vigor with which F. microcarpa grows, I expect the wire to be hidden within a couple of years.

And this tree has lived up to its variety's reputation: I had to replace the ties twice during the summer, when they began to bite too deeply into the bark! I replaced them a third time tonite, and decided to take some pictures.

Before work began. You can see how much the primary trunk has outstripped the other three.
I picked up the green ties at a garden center outside Suí an Róin, Co. Offaly.

The tree has been trimmed, and one of the old ties has been cut. You can see
the wire showing here and there along the left side of the partly-fused trunk.

Usually I try to have a new tie in place before I cut the ones above and below it. Ties are pulled snug.

The wire was cut off the upper part of the main trunk earlier this year.
Tonite I removed most of  the wire visible in this picture. 

A new set of zip ties is in place. The blue arrows indicate the length of wire that was removed tonite.
The rest will remain permanently embedded in the tree.

Trimmed, re-zipped, and settled in the Crate for the winter. Please forgive the somewhat blurry area near the base
of the trunk: a drop of water may have gotten on the lens. But of my "after" pictures, this gives the best view of the work.

As you've seen, the ties have left rings of obvious constriction on the trunk. But given the speed with which this fig grows, I expect those to grow out and disappear within a few years. By the beginning of next summer I expect the trunks to have fused together enough that ties will no longer be needed.

My provisional long-term plan for this tree is a modified broom with a broad, spreading canopy, probably with aerial roots dropping to the soil.

Sooner of later, I want to try this technique with another fast-growing species, this one temperate: bald cypress. I'll be sure to take pictures when I do.

:-)  :-)  :-)