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7 min read

Introduction

There are few species as versatile as the Chinese or Trident maple (Acer buergerianum). These plants are very hardy, respond well to many styling techniques commonly used in the art of bonsai and can be appreciated throughout the seasons as leaf colour changes or when they fall, revealing the inner structure {and the artists skill}. They can be styled in many different tree forms although informal upright and root over rock are most likely the most common. 

In this article I will describe the process I used to create this root over rock Chinese maple.

The beginning, 2011

I had a lot of young maple plants of around 3 - 4 years old, collected seedlings. I reasoned that it was going to take some time yet for these individual plants to reach a stage where they could be styled so I concluded to combine their individual trunks and have them fuse together to form a single trunk.

When and where possible use of collected seedlings or seedlings which have grown around or near the parent tree is prefered to develop plants from. These seedlings will have undergone a natural selection process and only the strongest would have survived, the weakest being culled by nature herself.

Furthermore I had not previously grown a root over rock so I thought I would give that a try with a rock which I had found while walking.

After exposing the green cambium layer of the inside of each of the trunks by gently scraping the bark off, I then cable tied them together although in retrospect if I had to do it again I would rather use parafilm grafting tape or natural jute rope. Both of these would degrade naturally so you would not have to worry about any scars left by non-perishable materials.

The rock you choose to plant your tree on should also be carefully scrutinized. That is to say it should not be made of a soft material such as sandstone which will over time crumble to nothing. Chinese maples and many other species such as Figs have incredibly strong roots and can easily crack softer stones. Consider also the colour; darker stones are preferred over lighter ones and white would be a challenge indeed. The reason for this is that the focus of the planting should always be the tree with the rock playing a supporting role. Light or bright colours  tend to advance, visually, where muted colours recede. Should your rock have veins of other deposits in them consider whether you will use these vertically or horizontally and how this is likely to affect eye movement in the composition.

The roots were placed as naturally as possible into or along fissures in the rock. Never place a tree so it appears perched on top of the stone. It is very unlikely, although not impossible, that something like this would occur in nature ie a seed falling on the crest of a stone and growing into an adult tree. Rather plant it off to one side or in a depression.

There is no denying that growing plants in the ground is the fastest manner in which to develop them, so I put the whole planting in my purpose built raised beds at home.

The trees cable tied together, secured onto the rock and planted into the garden bed.

When placing the planting in the garden bed I did so onto the top of a tile. Usually this is done to force roots to grow horizontally to enhance the flare of the trunk at its base. However in this case I wanted to use the tile to aid the roots clasping the rock by folding them under the rock so they would rest on the tile. Using a tile also makes it easier to eventually lift the tree from the ground as you simply need to sever the roots which grow off the edge of the tile, no roots growing straight down below the planting that are tough to get to.

Spring, 2012

One year later the plastic planting bag holding the growing media around the planting was removed. I should also add that a few months prior to that I had to remove the plastic cable ties holding the trunks together as they were beginning to dig into the trunks, which had completely fused by then.

The roots have thickened substantially as did the trunks. Fusing of the individual trunks was very successful.

Exposing the roots I found they had developed well and thickened substantially over the preceding growing season. However, I decided to leave the planting in the ground for another season so it continue to develop before transferring it to a container.

Spring, 2013

After another full growing season in the ground it was time to lift the tree.

The roots had continued to develop very well and the evidence of the process ie fusing of several trees to create the trunk had pretty much disappeared.

I reduced the trunk's height with a sharp, fine toothed saw and also cut off unwanted roots.

root over rock chinese maple on tile

After sealing the cuts, potting the tree into a container with a fast draining mix to encourage rapid root development I left the tree to grow freely for the rest of the season. Lots of fertilizer was used to support the growth in general, with occasional doses of Kelpak for root stimulation.

Late spring, 2014

The previous season's unhampered growth resulted in a tree of very good health. It is when a tree has such energy that techniques can be applied with a good chance of a favourable outcome.

Healthy, late spring growth is ideal to use for approach grafting.

Although maples do bud back easily, especially when cut back hard in late spring, where the buds emerge is very unpredictable. A more deliberate approach is grafting branches into positions you want. The most common methods are thread and approach grafting. Thread grafting is a very effective method but can only be performed in early spring before buds have swollen. Approach grafting however can be done at any time during the active growing season.

A number of grafts can be done at the same time, just not vertically below or above one another.

So rather than simply pruning off the long whips which developed in the previous growing season I opted to use their girth to achieve branches, in the positions I needed them, quicker.

Spring, 2017

Continuing the styling of the tree I decided to work on the roots in the spring of this year, while repotting it into an akadama/pumice medium and a smaller container.

Some roots which did not clasp the rock as well as one would want were removed with an appropriaely sized root cutter. On the right hand side of the planting a major root flared away from the rock instead of clasping it, leaving an undesirable gap. I decided to approach graft onto the root, the end goal being to direct sap flow into the graft and cut the thick root off.

Starting to build structure on a deciduous tree is a slow process to begin with, but as each growing season passes ramification increases exponentially.

Up in the canopy, work continued to further develop the structural branching. Sacrifice branching is used extensively to develop the girth of the branches to make a more natural transition between the trunk and branch.

Late spring, 2018

After defoliation in preparation for wiring. However tips are not pruned so as not to stunt elongation of the sacrifice branches.

The process of developing ramification on deciduous trees is a time consuming process, there is no denying it. There are no shortcuts if you intend to do it properly ie with branches tapering and forking at reducing intervals till reaching the outline of the tree's silhouette. The process involves growing out and cutting back, repeatedly. The cutting back aspect is one which some struggle with as it seems counter-productive. However the end result is structure which can be appreciated in winter when there are no leaves to hide faults.

Anthracnose has been a big fight for bonsai enthusiasts living in the Western Cape (as far as I am aware the rest of the country has not had the same challenge). The evidence of anthracnose fungal attack are leaves which do not form naturally and are stunted and "clasped." Internodal distances become virtually non-existent and although this species is very hardy if left untreated this problem weakens and can eventually kill your tree. You can read more about anthracnose here.

Spring, 2019

The tree appears anthracnose free so far and if this healthy condition continues I can expect good growth this season. My goals for the growing season ahead will be to continue to develop the basic structure of the tree using sacrifice branching, then to improve ramification with directional pruning (pruning back to a dormant bud facing the desired direction of growth).

One of many grafted branches, with dormant buds close to the trunk.

Wire is used to give some interest to branches however as growth rates are high one needs to be careful of missing wire bite as it can easily be hidden by the dense canopy of leaves which forms. Although wire bite on Chinese maples can to some extent be of use, it is to be avoided on Japanese maples at all cost as the evidence of it may take many years to disappear, if ever. On Chinese maples though, some wire bite can add interest to branches so long as it is not too severe, as these trees have very strong callousing ability scars are rapidly healed.

Roots are hugging the trunk nicely and the approach graft on the root is doing well.

I will continue to fertilize strongly using Bonsaiboost, replacing it every few weeks and then a weekly foliar feed of Seagro or Sea Secret. A monthly treatment of Trelmix and Kelpak will also be performed.

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