Post 112 Celtis Sinensis

I've been jealoousy reading recently about folks in southern states going on digging trips to collect all manner of bonsai desirable feral trees. That got me thinking about what we have here in SE Qld and the obvious answer is Celtis. Celtis Sinensis make fantastic bonsai here; they grow quickly, ramify well and the leaves will reduce down to a very small size. Just search for 'celtis bonsai' to see the standard achievable.

With our climate, some potted celtis will go through the deciduous cycle, producing a beautiful lemon yellow colour in the autumn. It is very unusual to see a celtis growing in the ground do so. They will do no more than take a short growing pause for winter.

The problem is that they like it here too much and have now been declared an environmental weed, despite the fact that in many parks and gardens there are some very fine mature landscape examples flourishing. The rules for environmental weeds are that they not be bought or sold. The seeds, spread by birds, germinate well in creek catchment and low lying damp areas, where they can crowd out the local flora.

As I've driven around the bayside lately I've been looking for the feral ones and have been surprised at just how many there are. In one place  I noticed a couple growing up through the long grass on a footpath. The area had obviously had some maintenance a couple of years ago and these two celtis had been cut off close to the ground.
What could I do but my community duty in removing these dangerous invaders from the natural environment. So that's what I did, roots and all, and brought them home to start a new life where they will cause nothing but delight.
These two trees are in the first two shots following. You can see the cut off stumps and also the new growth going over the top of the cuts.

The first one was growing on a small sloped bank and so has a nice bit of movement already in the quite heavy trunk.

The second one has produced multiple regrowths - plenty to chose from once it recovers. I've put these two in poly boxes to grow on. This one is a natural for a forest group.
This recovery capacity demonstrates the value in having a two stage collection process. Stage one is to cut the top off in situ and make the most of a strong root structure to drive vegetative recovery and then come along some time (2 years perhaps) later and disturb the roots; if they are still there!

I had found another site nearby that was weed heaven, full of celtis, ochna, lantana and asparagus vine; just amazing. There were two that I decided to take out entirely and many more that I just cut the top off for 'later'. The collected ones are back home now planted in the ground ready for spring.
 

This one was a twin with the main tree about 6m tall and trunk at the cut about 100mm in diameter.

The second was a fused clump, obviously a group of seeds in one bird dropping, with 5 trunks, and an elongated 'footprint'.

Both of these were growing in damp soil in an area prone to a bit of acid sulphate conditions and so the trees confined themselves to mostly surface roots. This made them comparatively easy to dig out and fostered the development of nice nebari already. All the trees I dug had good fibrous roots near the trunk and so have a good chance of recovery. I'm looking forward to seeing some shoots pretty soon.

Post 111 Tanuki No 4

After seeing all the Junipers in the deserts and mountains of the SW USA I have been inspired to make Tanuki no 4. I was particularly taken with the growth habit where the trunk and or branches have a ribbon like or ovoid cross-section, often with the live vein growing along the edge. So that was the inspiration for this tanuki. I also tried to bring in a feature of the trunk splitting at the base. It is in offwhite stoneware and fully fired, finishing up at about 330mm high.

This is what I think will be the front. Even though the apex bends to the rear it will be the live tree that comes through that final loop towards the front.

Left hand side.

Rear

Right hand side

I have some air layers underway on a Sargent Juniper which will be ideal for installation on the tanuki. The branches I'm layering are long and straight, long enough for the bends and twists to get to the top and flexible enough too; just perfect. I hope by late summer to be able to get on with getting them together.

Post 110 Why annealed copper wire?

Just before we get onto that I found a better illustration of what happens when we bend wire - illustrated on a stress strain curve.

We start by winding the wire onto the bonsai branch. Depending on the winding pitch and the size of the branch etc some parts of the wire will still be in the elastic range and some parts may have been bent far enough to reach the plastic range.

As we start to reposition/reshape the branch by bending it and the wire we take the wire into the plastic range between A and B. If you drop a vertical line down to the Strain axis that will show the distance moved.

As we continue to bend in the plastic range more effort is required because the wire hardens with the work being applied - it work hardens.

If we keep bending to C and then release the pressure, because we are no longer in the elastic range the wire does not retrace its path but follows the line down to F. So going to C meant that we bend the branch a distance of G and then when we take off the pressure it returns to F. That is without any consideration of the additional recovery forces applied by the branch which remains elastic, and wants to go back to where it started
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That's why when you use wire to bend a branch of any maturity you ALWAYS have to bend it further than you want to reach a certain position.

That analysis is based on the generic ductile metal curve. It gets really interesting when you start to look at the curves of the real data for Drawn Copper, Annealed Copper and Aluminium.

Annealing of copper is done to change its properties to become softer and more maleable, by heating to a high temperature and then cooling to change the crystalline structure of the material.

Thanks to Cambridge Uni for this chart.

The RED line is for Work Hardened copper - and with wire being made by a die drawn process it will be work hardened.
The BLUE line is for annealed copper.
The PURPLE line is for pure aluminium.

 So what does this tell us?

You can see that the work hardened copper has a short elastic displacement but with high effort. This says that relatively it takes much more effort to change its shape and unless you take it far enough it will come straight back. Once it yields however it doesn't work harden much and will continue to deform with reducing effort.

It gets more interesting when you look at the annealed copper curve. It basically has no elastic range, is easier to bend, deforms straight away and the more you bend it the harder it gets, all good characteristics for bonsai work and exactly why some would say that if it's not annealed it's not worth using. To put some cream on the cake the fact that it has no elastic behaviour means it is more likely to hold its position when load is released.

Now the aluminium. It has a short elastic range and then after that is like the annealed copper only easier to bend (and thus has less holding strength). But you can only take it so far before it will weaken and break. This data also shows that the peak stress of aluminium is about half that of annealed copper. In the numbers I was using in the last post I assumed it was 70% higher. If it is 100% higher you are going to have to use an aluminium wire of around 20% increase in diameter to match the annealed copper, so it's not such a big difference, but you still have the overbending/recovery to deal with.

 So today's conclusion are:

• Annealed copper is much much better than aluminium, in all regards.
• If you are going to use copper if it's not annealed you might be better off with aluminium.
• If you are going to use aluminium use a heavier wire than you would for copper and be prepared to have to overbend to get a branch to stay where you want it.

 Isn't it great when the science confirms what you already know.