Silver birch bonsai grows fast and dies back easily, but thrives if you finish all wiring and pruning by August and never start before spring growth hardens. Use 1.5-2mm wire for gentle arcs, encourage multiple primary branches instead of relying on one, and repot in spring with 40-50% akadama or bark to handle its high water demand.
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Betula, or birch, are an easy-to-obtain tree species for bonsai but are also known as being a very difficult species. Although they are very fast growing and fast to develop, they are liable to die back not only of individual branches but of trunks as well. The silver birch I'm working on in this video originates from Poland, with me as a commission to repot into this beautiful blue round pot. I have allowed the tree free growth this growing season, and now that the growth is slowing down, I'm wiring and pruning the tree. The tree has a very high quality trunk that is not only silver-white color but has started with mature fissured bark. My timing for working on this tree is also governed by the fact that it is important not to wire or prune birch after late summer, which is August here in the UK. Birch are an accomplished frontier species. This means they will establish themselves very quickly on empty land and can adapt to very dry or wet Hot or cold growing conditions. One coping mechanism that they have evolved is the ability to survive by rejecting damaged trunks or branches and resprouting from the base. For us in bonsai, this means if any pruning or wiring is carried out too late into the season, the tree is unable to heal before the onset of the cold of winter And that limb will simply be rejected by the tree and it'll die back. Because of the possibility of losing branches at some point, it is not advisable to allow the overall design to rely on any one particular branch. With birch, the standard rules of styling don't apply. For instance, don't worry about bar branches or multiple primary branches emerging from a single point on the trunk. When designing a birch bonsai, try to encourage more primary branches than you normally would. Then the loss of one individual branch will not destroy the overall effect of the tree. Try to keep on top of the sucker growth that repeatedly appears at the base, as the suckers will remove strength from areas higher up the tree. And remove dead branches and shoots during the growing season. Prune branches for taper where possible. As with all bonsai species, a tapering branch is an excellent way of showing age. Coarse growth is only acceptable in the primary branches themselves. Those branches that are wired downwards to weep should also taper where possible. I start putting wire onto the branches. 1.5 and 2mm aluminium wire is sufficient for 1 to 2-year-old growth. It is not necessary to wire the branches 100%, as it should be possible to wire sections of each branch so they arc over and then drop naturally. It should be said at this point that this is the way birch grow in lowland European countries. In mountainous regions and at altitude, Extensions are much shorter and branches do not tend to weep. Creating a natural arc in the branch is not as easy as it might look. New branches should grow upwards at first and then away downwards in a soft, gentle arc by their own weight. Try to avoid creating a very tight arc that drops too early, But also try to avoid creating a very wide arc that grows out sideways. There is no real structure to the primary and secondary branches on birch bonsai. The idea when styling is to simply fill out the overall foliage mass, allowing each dropping branch to fill out empty space in the canopy. Some branches that will require wiring and placing will also be allowed to continue the downwards path of existing dropping branches to extend them. The leaves on newly dropped branches won't look entirely natural for a few weeks after styling until they naturally turn upwards towards the light again. After 5 hours of wiring, and my work on this tree is complete, complete for now. Further extension of the lowest dropping branches will be developed in the future. As it is now near the end of the growing season, it is unlikely that the tree will grow much further this year, so the wire will stay on the tree until next spring when it starts to bite in. This will give the branches plenty of time to truly set in place. A second birch that I'd like to show you in this film is one I collected from the hill, a favourite collecting spot I have in the nearby Chiltern Hills. This one was collected 6 years ago and has stunning mature fissured bark and unusually good movement for a birch. It takes well over 10 to 15 years for the bark of a silver birch to change to the silvery white colour we're familiar with. The very similar downy birch will take even longer. Birch react badly to trunk chopping. Although they will continue to grow after being chopped back, It is very common for the wound to rot heavily and then die back, sometimes along the length of the trunk. Try to avoid collecting birch that you need to chop heavily yourself in case of prompting future dieback. This tree, however, and the others surrounding it were chopped hard by the landowner around 2 decades ago with a chainsaw and have been left without any noticeable dieback. My assumption is, is as the tree were relatively slow growing in the ground and in the conditions up there in the hills, the wood is very hard and has not rotted. There were a lot of these birch available for me to collect, and I collected a good number a number of years ago. Unfortunately, the landlord has now torn the rest of them out of the ground where they are considered a weed tree. This tree was collected in 2018 and within 18 months had been planted in a pot by Victor Harris of Avon Pottery. Such is the vigour of birch. The tree, a favourite of mine, has been allowed to grow freely this year, but with August fast approaching, I wanted to complete all pruning and wiring. Having been wired and styled 2 to 3 times in the past, this was a fairly simple task and involved pruning away unwanted extensions and wiring and dropping some of the new shoots to add to the overall foliage mass. A few further notes I would add regarding birches bonsai. Repot in spring using a free-draining soil. However, birch are a very thirsty species and need 40 to 50% akadama or chopped bark in the mix to keep it moist throughout the year. Birch respond well to root pruning, but go careful to chop thick roots to a smaller secondary root, lest the thick root starts to rot back. As mentioned already, finish all styling and pruning by August to avoid dieback. But don't prune or style before the first flush of growth in spring has hardened. Birch bleed sap excessively if pruned in early sap— in an early spring until they have pushed their first flush of growth. Despite being something of a touchy species, during the growing season birch can be pruned repeatedly if necessary and defoliated partially or completely at midsummer. I hope you've enjoyed this walkthrough of Bursas and Species for bonsai. Please like and subscribe for more.
