Betula pubescens/Downy Birch Bonsai Progression Series

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Betula pubescens/Downy Birch Bonsai Progression Series

This Downy Birch/Betula pubescens was originally collected in the Autumn of 1999 and chopped down from a tree of over 20ft in height. Though Birch are a very tough pioneer species and will tolerate collection in Autumn I was later to find to my cost that they dislike being cut back hard (trunk chopped), particularly from September through to April.

Unfortunately, no early pictures of the tree exist. It had been planted in my growing field to grow a new trunk leader and to heal the wound where the trunk chop had been made. Though the tree grew very strongly, one side, the 'back' of the trunk, died back along the length of trunk to the ground and began to rot. The above picture was taken after 3 years of growing in the ground and shows how a harmless bracket fungus had colonised the dead wood through the bark.

Betula pubescens/Downy Birch Bonsai Progression Series

The following Winter (2003) I decided to lift the tree prematurely and see if I could use it as a bonsai. Though the wood in the interior of the tree had become very soft and pulpy in places, the bark of Birch is very resistant to water and rot, and so was completely intact.

Betula pubescens/Downy Birch Bonsai Progression SeriesBetula pubescens/Downy Birch Bonsai Progression Series

The bracket fungus was cleaned away, the tree potted up into a spare Chinese pot and the branches wired. Given the habit of Birch branches to dieback if pruned while dormant, I wired all of the branches and avoided any pruning until the following April.

Though they bud out strongly, it is very difficult to force a Birch to bud out in any one particular place; the branches on this tree all came from the top and so a cascading style was formed to utilise the existing growth.

Betula pubescens/Downy Birch Bonsai Progression Series

2004. In an effort to stablise the rotting internal wood at the back of the trunk, I decided to treat it with wood hardener. Though the rotting wood posed no threat to the health of the tree, I did not want to incorporate deadwood features into its design. There was also a real threat that if the rotted wood were removed, the trunk would have inverse taper as the rot was wider and more pronounced at the base of the trunk.

I used a syringe to carefully inject wood hardener through the bark into the rotting wood. Drill holes were made into the trunk through to solid wood just to make sure that all of the rotten wood was hardened.

The resulting drill holes were then filled with wood filler and disguised by painting the bark with a mixture of (black, white and burnt umber) oil paints.

The treated area can be seen along the right hand side of the trunk in this image and continues right down to the base.

Betula pubescens/Downy Birch Bonsai Progression Series

The tree continued to grow very strongly. New growth allowed me to create new, more natural cascading branches. In Early June 2005, the position of the tree was changed slightly during its Spring repot. Growth has been strong and the tree has filled out rapidly. At present the trunk remains very stable, so next Winter it may be time to invest in a better pot.

Height of bonsai:21"/53cm

Betula pubescens/Downy Birch Bonsai Progression SeriesBirch bonsai

Late April and early May 2006. The tree was planted in a pot by Erin Pottery this Spring and it has just started to leaf out.

November 2006. Though the wood hardener applied two years earlier had slowed the rotting of the trunk, the interior was still very wet in places. The base of the trunk was still exposed in the soil and was acting like a sponge, sucking up moisture from the soil into the heartwood of the trunk.

I decided that it was pointless trying to prevent the rotting trunk from falling apart and excavated all of the soft, wet and rotten wood.

Birch bonsai

The remaining live wood and cambium is less than 1/2" thick but the trunk is still sturdy.

I have now decided to treat the hollowed side of the tree as the front; it seems to suit the tree, particularly during the leafless part of the year. For a closer look at this bonsai please see this video

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