Quercus cerris bonsai refinement techniques

This bonsai is in the process of refinement, an ongoing task for the rest of its life, though some thickening and strengthening of lower branches is still needed.

Technically the two processes of refinement and development can work hand in hand at this stage. The new growth will be repeatedly pinched on the apex, allowing some extension into open areas to fill out the winter tracery of branches. The same area will be partially defoliated, using both leaf reduction and removal of all larger leaves, once they have fully hardened off.

These techniques will force energy down to the lower branches, allowing them to push more new growth and encouraging back budding. The process works by the reduction of apical auxin, auxin  concentrates in the extending buds and suppresses lower branches causing strong apical dominance. At the same time  defoliation will allow light to penetrate the canopy, allowing the lower branches, and any stimulated back budding, to photosythnisise more and therefore lay down more vascular tissue, causing them to strengthen and thicken.

These techniques are applicable to any deciduous bonsai in refinement, though each species has nuances to how they are applied and the health, and recent work on the tree, have an influence on how and when they are used.

There's more than one way to achieve this result, but for me this works well. Before working this out, I nearly lost the lower branches due to the strength of the upper canopy.

When this tree was in a deeper training pot it's vigour was hard to manage, but the sub trunks we're easy to thicken. Horticulturally the current pot is doing the right job, but the aesthetic will be improved by a very fine glazed ceramic. I have a Peter Krebs pot on the way and it should go into it next spring.