Korean Hornbeam repot

Mark brought his Korean hornbeam for some help in repotting. This tree was purchased several years ago from Bill Valavanis at International Bonsai Arboretum. It is a collected Korean hornbeam stump that was then grown for ten years in the ground before being imported to the U.S.

The main defect in this tree is its field-grown trunk, which is obviously the middle third of the trunk line. It lacks any kind of taper, and has some movement that is without doubt, man-made. Other than that, the tree shows great potential to be a great tree.

One could chop the trunk two inches above the collected trunk and regrow the trunk in successive cut backs, but that would require at least 15 more years of work on the trunk alone, with much of that time in the ground. A better solution might be to train some foliage across this bit of trunk to disguise this flaw.

Mark and I repotted this tree in approximately 2003 or 2004 and put it in this pot. At that time, it was bare rooted and potted in the oval mica, which was the biggest pot we had available. It would have been better to build a grow box specifically for this tree, but time did not allow.


In the ensuing years, Mark has repotted the tree several times, always putting it back in this pot. Like many enthusiasts, he was a little worried about being too aggressive with root cutting. This tends to produce a tough root mass that is difficult to work with. Fortunately, in every other way, Mark made this three extremely healthy and vigorous, providing a good bit of material for this repot.

Following the guidelines in my article, "Repotting an Established Bonsai," we removed the tree from the pot and set to work on the roots.

This tree has an excellent nebari which we wanted to expose in the repot. The roots were fairly tangled, so we set about sorting them out. The angled tweezers included with most bonsai tool sets work so much better than a chopstick in sorting out roots. They are gentle to the root tips, and there are two ends instead of one, which really helps in moving the roots.

The point here is to encourage every root to move in a direction directly away from the trunk. Crossing roots are either moved or removed. In other words, if you can redirect a root without damaging it, do so. If you cannot, you might want to get rid of it.


This tree is in excellent health with an abundance of fine roots, which provide the tree with its nutritional requirements. The nutrients provided by fertilizers (along with oxygen and water) are absorbed by the root hairs and transported by the xylem to the leaves, where photosynthesis transforms them into carbohydrates. The carbs are then transported to the roots via the phloem.

Mark sorting out his roots.

We work on the base of the tree, seeking to remove all the old soil and direct all roots toward the edge. If roots are coming directly from the base or moving underneath the tree, they must be removed. All roots under the base of the tree will ultimately raise the tree in the pot.

For trees in the ground, large roots perform several functions. The first is anchorage. Large roots keep the tree stable in the ground and enable the root hairs to be secure and do their work. Another is the storage of carbohydrates for less-than-desirable environmental situations. Both of these uses are negligible in the bonsai pot, where we tie the tree into the pot for stability and feed heavily with fertilizer to provide the tree with what it needs. Therefore the most important roots for bonsai are the root hairs.

Here we are using the water jet to remove extra soil and ease the root sorting. It's a process of manual root removal, washing with the hose, and repeating the process. In this case we used the hose twice. With nursery material, more trips to the hose might be necessary.

When a bonsai has a tremendous amount of fine roots, one can be fearless in arranging and trimming them. When a tree has sparse or incomplete roots, one should be careful to keep as many as possible.

Viewing the tree from beneath, one can see the trunk base where the roots have been worked previously. Good work on the base of the tree guarantees future ease of root work as well as a flat root ball.

The final image.

The tree is repotted into a glazed Korean pot. It's not the ultimate pot for this tree. Ultimately, this one might take a glazed or unglazed oval pot. The branching is immature and needs to be rebuilt, but with the root work done today, branch work can wait a year.