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Discovering the reason why a bonsai is dying can often be difficult to establish. Very often the cause with beginners' trees will be underwatering (the soil being allowed to dry out) or a tree that has been purchased growing in poor, congealed soil.
However, bonsai can occasionally show poor health, even in the hands of more experienced bonsai enthusiasts. Establishing the cause in these circumstances is just as important in order to avoid the same problem re-occurring.
The Juniper bonsai featured in this article was owned by an experienced enthusiast and its foliage had suddenly started to brown and die. By the time the bonsai was passed to me to try and save, half of the foliage mass had browned-off and died.
The pedigree of this tree, a Juniper chinensis, is that it once grew in a garden in Japan, had been imported into the UK in early 2000's and ended up in the hands of the current owner for a considerable amount of money.
Strangely, although over half of the foliage mass had died, there was still a sizeable amount of healthy foliage left. This immediately suggested that for some reason, a portion of the rootball/rootmass had died, causing the top-growth it supported to die off as well.......however, the remainder of the rootmass was probably healthy and as consequentially its connected foliage remained healthy.
There was some evidence on the dead and live branches of spider mites, however, insect attack is often a result of poor health in a tree, rather than the cause.
Prior to work, the appearance of the Juniper bonsai from the front. (In many of these images, the tree and the Brian Albright pot it is planted in, are placed inside a possible alternative pot, ultimately I decided to keep the bonsai in its original bonsai pot).
While my apprentice removed dead foliage with scissors, I wanted to be able to inspect the soil surface and began to pull away the various weeds that had sown themselves there. With the weeds removed, it became obvious that the tree had a nucleus of broken down Akadama (low-fired bonsai soil that quickly turns to a sticky clay) around its roots and this had been placed into a good quality soil, consisting of fast draining high-fired clay granules. As Junipers cannot be bare-rooted and all of the Akadama removed all at once, planting a tree in this way is quite common and allows the tree to root itself into the new soil while the Akadama is removed over a number of years.
As can be seen in the image above, the Akadama was very dry despite the surrounding soil still being moist. This can happen when Akadama becomes compacted and no longer accepts water (instead of being absorbed, water runs off its surface). My initial suspicion was that the parts of the root system still growing in Akadama had therefore dried-out and died, with the resulting loss of foliage. This would then explain why the rest of the tree was alive and healthy, those roots not growing in Akadama were also healthy.
This is a fairly common problem with coniferous species such as Pines and Junipers, planted in Akadama and to rectify this, I tend to remove all the Akadama that I can using a chopstick, without disturbing any live roots. The Akadama is then replaced with a high-fired inorganic soil and this is normally sufficient for the tree to recover slowly over the following growing seasons.
As I gently pulled away the Akadama, leaving a large number of dead fine-feeder roots that had obviously died recently (as they had not had long enough to rot and crumble away completely), I was surprised to find a large void underneath the section of the rootball and the real reason for the death of one half of the tree became immediately obvious.........
.......Seen from the right hand side of the bonsai, I had noticed that the planting angle of the Juniper had been changed in the recent past and the tree had only been secured with one (fairly ugly) tying-in wire. The owner of the garden in which the tree had been living for the past couple of years suffers very high winds and I realised that the tree had been turned slightly in its pot during a high wind, leaving the roots on one side of the tree in a void with no soil, quickly leading them to dry out and die.
A good reminder to always tie-in a bonsai very firmly into its bonsai pot, if ever I saw one!
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