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Decline & Dieback

by Carl Morrow

When you start out in bonsai you enthusiastically lap up all sorts of generalised advice, storing it away for future reference. Soon the phrase a little learning is a dangerous thing is driven home, as you feel more useless and uninformed the more you investigate the art. You come to realise that in order to grow good bonsai you need a different range of techniques that are unique to each species.

Olives are just such a case. Remember the way in which senior growers would expound the virtues of the olive, the way in which bare stumps can be collected, its tolerance to bright sun and low water and the ease with which the trunks bud out. "Never mind if you don't have a branch in the correct place, it will oblige and throw one out for you."

Fourteen years after collecting my first olives I am still trying to work them out. Yes, big stumps can be collected but sometimes they grow immediately while at other times they can sulk for 2 to 3 years before sprouting. Yes, some of the trees thrive in hot, dry, windy conditions while others seem to prefer more sheltered spots with more water. And yes, branches usually shoot out of the trunk at desired points, but I have waited over 10 years for some of the trees to do so!

It is important that you know which tree you are working on, as there are distinct differences among the habits of the European Olive (Olea europaea), Wild Olive (0 europaea ssp. africana), Coast Olive (0 exasperata) and Ironwood (0 capensis). For example, O. exasperata has a weak root system and the wood is much softer than 0 europaea ssp. africana and is thus less suited to deadwood work. European Olives tend to show coarse, angular growth with bigger leaves making them more suited to larger bonsai.

In the early days (now I sound old!) of my bonsai interest, the Dremel and then the die grinder were discovered. They were wonderful tools that could be used to create a multitude of very beautiful, sculptural masterpieces with a minimum of foliage scattered around the beautiful trunk. It certainly was a great development in the art, however I started getting concerned that on some ofthe trees the carving had gone too far, thus jeopardising the survival of the tree. The most memorable example had been completely hollowed out and my concern was that the sapwood in the tree was now exposed from the inside and so, as it dried out it would die through the wood into the cambium from the inside outwards and thus harm the tree. To my surprise the tree did survive and was on show last month, but it did suffer some die back on the trunk that had to be incorporated into the design. See figure 1.declinefig1Figure 1. Olea europaea spp. africana, Wild Olive. Artist: Len Redfern

Another example of severe carving was a tree that started off with a substantial, living trunk, which was reduced to a predominantly dead sculpture with a very thin bridge of live bark running up to the apex. My predictions of trouble with this tree were borne out and eventually the apex of the tree died leaving a much less attractive tree to be re-designed.

The bark on the trunk of the first tree that I carved laterally died back to a point about 10 em from the original carving. Subsequently, slowly over the last 13 years it has developed a roll of callous 5mm thick. I think these problems were caused by the speed with which the trunk was killed and exposed which did not allow the tree a chance to re-establish the nutrient and water supply channels within the trunk. The lesson learned was that one needs to be more careful with carving of trees and ideally do it in a two step process. The initial definition of the design followed by a re-establishment period where regions of the trunk are allowed to die back to their natural flow lines. Once this has occurred, the refinement of the deadwood is done by taking care not to carve into any existing live wood otherwise you will repeat the problem that you were initially trying to avoid. It is for these reasons that I now look for trees with existing deadwood that can be refined as I am then avoiding the problem of unexpected and unpredictable death on the trunk of collected trees.

When one is working on old Juniper trees one of the first steps is to identify the live and dead regions on the trunk. This step was highlighted by Mr Cheng during his visit at the end of 2000. Once one understands the flow line structure of the tree one can then go ahead and design the tree. This underlying bark structure is particularly obvious in junipers for two reasons. The wood structure of the trees means that there are quite strict, defined channels through which water flows and the bark of the tree is quite thin meaning that if the outer layers are peeled off then the live and dead regions of the tree become obvious. I feel that the same effect is occurring in olives although it is very much more cryptic. The bark is much thicker and when it ages it becomes corky and rough, which doesn't change in appearance when the underlying tissues dies. The channels are also less defined and so one need to be very much more careful when isolating the flow lines on an olive bonsai.

This slow death of tissue is emphasised by Rudi' s humorous assertion that the best collected olive trees are those that were dug out ten years ago by somebody else. This is because it takes up to ten years for the tissue in the trunk to die back to a stable position and so what starts out as a spectacular tree can become second rate as sections of the trunk. die off and the branch arrangement becomes more and more limited. Another problem has been clearly demonstrated by Evzen where he had a truly beautiful tree (one of the best olives that I have seen) and in order to get it into the pot that he wanted it to be displayed in he cut through a heavy root on the one side of the tree. Shortly thereafter the whole side of the tree died resulting in a tree that was a mere shadow of its former self, to use a horrible cliche.

What is the cause of this tissue die back? A way to think about it would be to imagine an analogy of a business such as a supermarket chain. These companies will only support regions that are being productive. There is a flow of products from the suppliers and farmers (roots) through the transport network and supply chain (trunk) ending at the shops that sell the produce (leaves). The shops are the units that earn the money that supports the rest of the business although they (the shops) are reliant on all the other units to keep the money rolling in. Various attacks can be made on different steps in the process. If a great big new shop is opened next door to the small supermarket then the new, dominant shop would overshadow it and so the smaller shop would shrivel and die. When this happens the trucks supplying the shop would have to try and fmd somebody else to supply or they would have to cease operation. This lack of demand from the terminal regions of the business (leaves) can therefore have an effect on closing down the supply chain (sections of the trunk) and even the roots (no market for the farmer's products causing them to cease operation). From this analogy one can see that bonsai artists need to consider all of the components of the tree (leaves, branches, trunks and roots) so that any detrimental effects resulting from work done on the tree can be minimised. When you are designing a tree and doing carving you need ensure that enough foliage will remain in the final bonsai to support the living bark that you are leaving.

So the question remains how do artists like Kimura achieve such dramatic sculptural masterpieces with their trees? I can think of two reasons. Most of the trees used by these artists are conifers that naturally develop twisted and gnarled deadwood combined with ribbons of twisted live wood. The other factor frequently missed is that these trees are generally very much bigger than the specimens we are using. This means that regions supporting lush canopies but appear impossibly thin are in fact quite large, a few centimetres wide and equally thick and so the xylem and phloem can function properly with no risk of damage from external drying etc.

declinefig2Figure 2.Another aspect of olives that is rather mysterious is a problem that has been around for a long time but is only now being articulated and attempts are being made to solve the problems. Two disease-like symptoms are apparent.

One is where the tree stops thriving, starts growing weakly and tends to drop leaves early leaving sparse foliage on the tips of ramified branches. Attempts to stimulate new growth by pruning only results in scattered vertically oriented shoots that upset the profile of the foliage pads. Little lateral growth occurs. This would indicate a disruption of the whole functioning of the plant and would be consistent with a root damage. I first heard about this problem while learning bonsai with Bernard Coetzee. He always talked about the ten-year slump in collected olives: The trees would be healthy and grow vigorously for about ten years and then they would start to loose condition and go into a decline. People recommended solving the problem by planting the trees in large pots or in the ground for a year and allow them to grow unchecked for this time. John Naka apparently also had these troubles with trees such as cotoneasters and the solution in California was to bare root the tree, wash the roots in water and then plant it up in pure river sand to allow the tree to regain its strength. People are now attributing these symptoms to the disease agent Phytopthora a common root pathogen found in many crop plants in the Western Cape and around the world. Susceptible species include proteas, silver trees, petunias, avocados, pineapples, citrus, pyracantha and cotoneaster among many others. The disease causes the death of the plant's root hairs, which then disrupts the efficient uptake of water by the plant. We can currently treat it with either "Ridomil" or "Alliette". Rudi has found that the more composty the soil mix the more problems one has with this disease and so it is best to wean sensitive trees off compost rich mixes onto more lean, sandy and free draining media. He also recommends that welllmatured compost will reduce the prevalence of the pathogen.

The other problem manifests itself by a few branches suddenly dying on an otherwise healthy tree. It is a process that can occur in less than a week. On day one the whole tree is healthy. By day three the leaves on the affected branches appear grey green with no vibrance and by the end of the week the leaves are brown and dead. This sudden death is clearly a problem of water supply to the affected branch and so would be consistent with the problem identified by Lionel where he found that the larva of the gall midge bores into the branch, destroying the cambium and the functioning of the branch. If one peels the bark away from the base of the dead branch one may see the pest as a small pink soft-bodied larva. This pest can also introduce a soft rot fungus into the tree causing further damage. Lionel finds that "Garden Gun" (containing Malathion) is effective against this pest. Rudi has also found that winter spraying with lime sulphur has limited this problem too.

This is a large branch of a tree that had naturally layered itself into the ground near the mother tree. It was collected 5 years ago with one small root on one side of the tree. It has never been a vigorous tree with sections of the trunk dying off as it retreats to only the most productive parts. The most recently affected region can be seen with the death of the shoots along one of the "muscles" of the tree, marked with the arrows.

The tree in Figure 3 is a very good demonstration of the need to very carefully examine the ridges or "muscles" on a tree in order to establish exactly where the sap is flowing. In this picture one can see the live and dead channels on an old tree (this particular one was collected in 1986). When I started working on the tree I though that the sap was flowing through the top ridges but on closer inspection it was found that the sap was in fact following a more complicated (and interesting) route along the bottom ridge and then crossing over the trunk up to the living branches.

declinefig3Figure 3.

declinefig4Figure 4b.

declinefig5Figure 4a.

 

 

 

 

 

 

 

 

 

 

 

 

 

These pictures (4a & 4b) of one of Len's trees show the final and most extreme outcome possible in this process. The whole trunk has died off leaving a thin channel of live wood running up the dead wood to the foliage. The foliage and root system are supporting each other via the most economical route possible. There is no wasted live bark here. As time has passed this flow line has grown, thickening and is now beginning to stand out as a ridge running up the trunk. An amazing demonstration of the tenacity of a tree.

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Tying roots - Rubber rings (approx one centimeter thick) cut from a motor car tube, have many uses. For example use to tie roots in a Root over rock planting - they also make good garters!