Horticultural Processes and Bonsai: Transpiration

Have you ever wondered how water travels from the soil into the roots and then up the stem to the leaves? Well, here we go. The process is called transpiration and starts in the roots through a process called osmosis. This is the movement of water across a membrane from an area of higher pressure to an area of lower pressure.

Now I am going to confuse you completely. I already said that it starts in the roots, but the condition for the process to happen actually starts in the leaves. As the water accumulates in the leaves, the internal volume of the leaves now have a higher pressure internally compared to the atmospheric air. That means that the water leaves the leaves through a structure called a stoma. There are hundreds of these on the leaves and they can open and close depending on the plant’s water needs and the climate on the outside. Almost like little valves.

Transpiration

Osmosis

Now we have the picture on both ends of the tree. The water flows in through the roots due to water pressure in the soil, it moves up a bit in the tubes (xylem) as these are very thin and act like thin straws. Have you ever noticed how when you place a straw in water how the water level in the thinner straw is higher than the level in the water. That is called capillary pressure.

What now happens is all of these work together. The water is pushed into the roots, the narrowness of the tubes give it a bit of a head start and then the pull from the leaves draws it further up the stem or trunk and the flow happens. This can happen as fast or as slow as the conditions dictate. If everything is perfect, a continuous flow will happen, but as soon as something changes, the tree will adapt. Let’s say there is not enough water in the soil for the osmosis to take place. In other words the pressure is not high enough for the water to enter the roots through the different membranes, well, water will not be taken up and the tree will dry out.

At the other end things can go horribly wrong as well. Let’s say it is a very hot day and a dry warm wind is blowing. That means the pressure on the outside of the leaf is very low and if there is any water inside the leaf, this steep difference will cause water to evaporate or transpire through the stomata and if this happens rapidly and the cells lose their turgidity (pressure), it will wilt and lose structure. If this happens for too long, it is possible that the plant will dry out and leave this earth for Bonsai tree heaven.

Before we get to the practical things to do and look out for, it is important to remember that water travelling through a plant will contain minerals and other chemicals that it absorbs from the soil. It therefore plays a very important role in the distribution of these minerals throughout the tree.

The practical things:

  • Watering is a very important part of keeping Bonsai and comes down to a balancing act to ensure that optimal conditions exist for the processes as described above to take place.
  • Make sure that your trees are placed in an environment that suits the watering needs of the tree. Plants with thin leaves that can dry out easily i.e., Maples and should be kept out of harsh sun and dry windy conditions.
  • Trees with smaller leaves or even needles (Pines) can withstand this a bit more as they have less stomata and a thick waxy cuticle that covers the leaf or needle to minimise the area exposed to sun and wind and therefore slow transpiration down.
  • Get to know the water requirements of your trees and if possible group trees with similar water requirements together.
  • Check the drainage of your trees regularly. This starts with ensuring that the potting medium / soil is correct for the type of plant. Plants that thrive in drier conditions will have to be planted in a coarser and free draining medium.
  • When watering, water from the top over the whole tree as it washes dirt off the leaves to enhance transpiration as well as photosynthesis. It also cools the plant down so not to lose too much water.
  • If the soil is too wet, root rot can occur. This is not necessarily due to something going wrong with transpiration, but more a case of the roots not being able to breathe. Yes, they have to breathe as roots consists of living cells and through the process of respiration, need to take in oxygen. More on this in the next article in this series. It is also a perfect living condition for fungus that causes root rot.
  • Other techniques to ensure the soil does not get too wet is to tilt the pot during long periods of rain for water to run off. You can also push a rod through the drainage holes through to the top to create a channel for water to run through. These are drastic measures only to be used in circumstances where you need to get rid of water quickly.
  • Soil can dry out very quickly in a small Bonsai pot. When you get to a situation where the soil is so dry that water on top just runs off the surface, break the surface up a bit and dunk the whole pot in a container of water. Wait until all air bubbles disappear and place it back on the bench.
  • Another thing to look out for is when the roots grow so fast that it basically replaces the soil in the pot and all you have in the pot is a ball of roots. It is difficult for the plant to absorb water under these circumstances. Prevention is better than the cure. Repot with fresh soil when necessary and treat your trees as if they are pets.
  • When pruning, cover the cuts with cut paste or something similar as you create a wound and in the context of this article, a leak. Plug the plumbing to support the flow of water through the tree.

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Bonsai – Good comes from bad.

One thing that is for certain when it comes to Bonsai as an art form is that it is never static due to horticultural and climatic influences. Then we have to throw pests, disease and the odd mishap into the equation as well. This little Thuja did meet up with a bug or two one night and the Thuja came of second best. Yes, whatever it was, ringbarked one of the branches and the first sign was that one branch changed colour. Obviously unhappy and on its way to Bonsai afterlife. What to do?

Change direction and from an informal upright change character to start the next phase of its life as a wannabe literati tree. The on its way to death branch comes off and becomes a jin.

Next step is to wire the trunk to the top, give it a bit of a change of direction and reduce the foliage as with the potting comes a reduction in root mass.

The tree is healthy otherwise and with good aftercare will grow into its new life and again stand tall as a proud Bonsai somewhere in the future.

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Garden trees to Bonsai

Let’s get one thing out of the way first. The term Yamadori refers to a tree lifted from the wild where it has spent many years, showing good age with features that will make a great Bonsai. When a tree is lifted from a garden or from any other place for that matter it is not a Yamadori, not even an Urban Yamadori as some people refer to it. Yamadori in my mind is for one thing and one thing only.

I have recently seen a photo of a very nice Magnolia Bonsai tree and wanted to try my hand at one. As luck would have it, a garden tree that was to be removed was advertised in my area and I jumped at the opportunity.

What we have here is a garden plant that has been grown as an ornamental plant in a garden bed. It is a Michelia figo or a Port wine Magnolia. It had to be removed as the owners were in the process of remodelling this garden area.

The original “plant”.

Great was my surprise when I parted some of the branches and discovered that it is actually three trees. It is important to make sure that there are no irrigation or other hidden water or electricity services going close to or underneath the digging area. The first job is to reduce the branches and foliage to get closer to the trunk and this will also help with survival as the branch and leaf mass needs to balance the root mass. Through the digging process and also the potting process, the root mass will also be reduced. And then the digging starts.

Branch and leaf mass reduced.

This was an easy dig as there are no tap roots and especially the two in the back were in quite dry loamy soil and they came out with just a spade length pushed into the soil about thirty centimetres from the trunk and circled around each plant.

The Three Musketeers.

It is important to leave the site in a tidy state and in this case I also removed the green waste for the owners. Each tree received a good spray of medicine water. Medicine water for me is just a weak solution of a marine-based or algae-based tonic across all parts of the tree. Now it is homeward bound.

The best advice is to have the planting containers ready before you go, but probably not so practical as you never know how big the root ball will be. in this case I used plastic planting pots, deeper than what a Bonsai pot will be, but this is to allow space for finer root development.

Good drainage is essential.

The first thing I do is to work through the roots. Remove all of the old garden soil and in this case some fat earthworks as well. Next is to remove very thick roots and reducing the depth of the root ball. Leave enough finer roots to feed the tree. I also apply rooting hormone powder to the cut roots and sprinkle a bit over all roots. Depending on the species, but more importantly, the state of the roots, I also apply sphagnum moss to the cut roots at this stage. In this case I did not as there were enough roots and they were healthy.

Next up is to find a possible front of the tree by finding the widest part of the nebari and lining this up with the best flow that the branch structure allows. This is also the time to now reduce or shorten the branches to fit this vision of what the future tree could like like in five to seven years. At this stage I do not remove all branches to limit the tree to just one or two styles or designs. In all three cases it is possible to highly likely that the main trunks will be shortened over time. as the pots are round there is no need to worry too much at this stage about the front of the tree for planting purposes. Just focus on what might be needed for future development.

Now for the planting. Good drainage is essential. The soil that I use for this type of planting is a 1:1 ratio of pumice and compost. These are broadleaf trees and will grow relatively unchecked over the next year or two. They will all be heavily fertilised as soon as new growth comes out. The compost base helps with this and the pumice provides the necessary drainage.

The soil is heaped up in a dome shape inside the containers, the tree is pushed down and wiggled into the soil, tied in with wire and then filled up to the top level. I use my fingers and then a rounded dowel to work the soil in-between the roots. All that is left now is to water the trees and to let them rest until spring when the feeding will start.

Updates will follow as these trees develop. I usually tend to keep one if I have multiples from the same type and sell the others. That just means that updates at times is on just one or two of the trees as the others might be making someone else very happy.

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Bonsai Branch selection 101

Have you noticed how most answers to Bonsai related questions starts with “It depends”. The main reason for this is that we are working with a living organism and it is very rare for generalisations to be applied across all trees. The list below are guidelines to use, especially when styling a new or starter Bonsai tree and applies very much to the more classical Bonsai styles. There will always be exceptions, but here goes.

Branches within the lower one third of the tree. These branches should generally be removed as it helps to show the trunk line. It will expose the nebari and allow a clear view of the bottom part of the trunk where hopefully is some great interest. This can be either well-developed bark, interesting roots or some type of movement lower down in the trunk. There is an exception (I told you so!) and that is when you deliberately wants to leave these branches as sacrifice branches to help with thickening the lower trunk.

Branches pointing directly at you. The main reason here again is to allow the main trunk line to be visible. The exception is in the top third of the trunk / tree, especially if these branches are part of the apex of the tree.

How about this Jin? Should it be removed? Maybe just a slight turn at the next repot and it is not pointing at you anymore.

Bar branches. These branches are ones that originate at the same level as other branches. If they are directly opposite each other, it is known as bar branches. Another issue with too many branches originating at more or less the same point is that a lot of sap will floe through that area which leads to an unsightly thickening in that area and could also be the reason for reverse taper. This is a thickening at that point with a narrower trunk below that point. Remove as many of these as you can, especially found in pines where the branches for a whorl, preferably leaving one as part of an alternately opposite branch scheme. Select the one that fits the rest of your design more naturally.

Look at the bottom two branches. Not on the same branch, but still opposite each other, forming a bar branch.

Parallel branches, usually originating close to each other, but directly above each other. This is more for aesthetics than growth patterns. The classical design of a branch to one side, then the next one up on the other side and then maybe a back branch and to be repeated as you move up the trunk, is the ideal and not always possible, but at least a good guideline to keep in mind.

Two parallel branches. What to do?

Branches growing from almost the same point. This relates very much to the last two guidelines, but in this case refers to branches not necessarily growing parallel above each other or from the sight height, but just close enough for it to be unsightly. There is always the possibility that this will also lead to a situation where that area can thicken disproportionately compared to where other branches grow from to the increased sap flow.

Quite a few growing from the same point or level.

Unusually vigorously growing branches. These branches take energy away from other branches and can cast a shadow across other branches due to its faster growth. It is also possible for these branches to thicken disproportionally to other branches and interfere with normal taper or the notion that branches lower down the trunk should be thicker than branches higher up the trunk. These branches should be shortened or removed.

Secondary branches growing from primary branches where the growth is in the wrong direction. This could be branches growing straight up or straight down, branches growing outside of the main design contours or even in the opposite direction of the flow of the tree or just that part of the tree or branch.

The leader. Older trees show a more rounded apex and this can be achieved by removing the leader, substituting it with a new leader or wiring it in such a way that it shows a more rounded form. This also helps with reducing apical dominance in trees and redistribute the energy in a tree.

As mentioned earlier, very few trees allow the opportunity to apply all of these guidelines, but it is still a good idea to keep these in mind as you work through the tree, selecting which branches to keep and which to remove. This is a video of the branch selection of a Camelia clump lifted from a garden. https://youtu.be/MeCBk-_ofEw

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Bonsai as Sculpture: An Art Form

Sculpture is defined as Three-dimensional art made by one of four basic processes: carving, modelling, casting, constructing, by http://www.tate.org.uk. A good friend and fellow Bonsai Artist, Greg Tuthill (http://gregtuthill.com/), is a sculpture artist who uses metal as his preferred material and, as mentioned, a very good Bonsai artist as well. That made me think about Bonsai not only as an art form, but specifically as Sculpture.

One of Greg’s sculptures.

Let’s unpack the four basic processes as listed in the definition above.

Constructing – Modelling – Carving – Casting

Constructing: For me constructing is producing or making something out of raw material. Here we can argue that the raw material is represented by the starter Bonsai plant, the cutting, the Yamadori or nursery material. From this point you have to make decisions about direction, flow, what to keep and what to discard. You cut, you wire, you shape and you bend what you have in front of you into a design or shape that resembles your idea and vision of what a Bonsai tree should look like. At all times the material that you are working with will dictate how far you can go and what is possible, You construct and therefore Bonsai ticks the box for this element of sculpture.

From Pinterest

Modelling: Modelling is shaping something based on a model and in Bonsai we have plenty of examples of this. The basic Bonsai forms of formal upright, informal upright, cascade, slanting and a whole lot more provides the models that we work from. This is used as background knowledge and applied to the material that you have in front of you to create something that might show elements of the model, but is unique in its own character. The act of wiring is also part of modelling.

Informal upright style model and a real tree.

Carving: This we see in Bonsai when we sculpt deadwood, Jin, Uro and Shari. For this we use various techniques and equipment just as a Sculptor would do.

Casting: I am not aware of a lot of casting going on in direct relation to the tree, but no Bonsai is complete without its frame which is represented by the pot. Various methods are used to produce or create Bonsai pots and casting is definitely one of these techniques. It is necessary to have a suitable container or pot to complete the full picture of what a Bonsai represents.

There is one major difference and that Sculpture is normally seen as something done with wood, clay, stone or other non-living materials. Bonsai is definitely done with living trees and can therefore by seen as a living art form. Is Bonsai a form of sculpture? In my opinion, yes, it is.


Yes, we are Sculptors as well as Bonsai Artists.

Lockdown Bonsai work.

We were supposed to have aBonsai Society meeting today, which would have been the first one in a long time. Last night at 9pm, a change in alert levels was announced which means that where we live, social distancing is in place and as the venue is quite small, not the best for safety in the current Covid climate. That was called off.

I had this tree that I wanted to work on at the meeting. Basically just a clean up job and then lots of wiring to set the foliage pads. It is a Pine tree and in the twin-trunk style. Here is the before photo.

Before the wiring commenced.

And here is the tree after the pads were set.

Cleaning, Jin work, wiring and branches set. Pity some of the three-dimensionality disappears in these photos. Maybe I just need to get my photography sorted.

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Critiquing of Bonsai Trees

In Robert Steven’s book, Mission of Transformation (2009), he mentions in the Foreword that Critique has become a favorite tool of his as an effective way of teaching and learning. It is my experience that most clubs or Bonsai gatherings will include some or other Critique session, especially at large scale exhibitions or shows. It is customary for the head Judge or a visiting Demonstrator to undertake this task.

I have been witness to many of these and have also done my fair share of these Critique sessions. One of the most important aspects of these sessions is exactly what Robert points out in his book and that it should be an opportunity to learn. It is therefore very important that it is done in a constructive way to enable not only the owner of the tree, but all the spectators to walk away with more than just the negative aspects of the tree under discussion.

I like to start these sessions by asking the owner to tell the story of the tree. This gives you a good understanding of the history of the tree and by asking questions, dive into the aspects that really matter. Once this part is done, I like to first point out all the positives. Find something, even if there is very little to go with. There will always be a positive. As the focus is for this to be a teaching and a learning experience, lead the discussion by questioning. Use open-ended questions and allow as many people in the group as possible to answer and become part of the conversation. It becomes very boring if it is only the Commentator delivering the commentary. There is a danger here in that you at times have a very vocal participant who gets so excited that they tend to dominate the conversation. As you are leading the Critique, be aware of this possibility and gently bring the conversation back to focus on the tree and the whole group.

A good place to start is the overall picture or story that the tree on display tells. Look at the whole scene. After that, I prefer to start at the bottom and work my way up. Lead a discussion on the pot, then the surface soil and covering. After this it is the turn of the Nebari and then the trunk. From here, discuss the style and the appropriateness of that for the specific tree. The next part will be the branches and the foliage before the critique almost reaches its end with the apex. Once all aspects have been discussed, it is really important to summarise and come full circle to the positives and then end off with one or two actions for future development of the tree.

It is a time consuming exercise and in the case of a display with many trees, I prefer to only go with the three top trees and then also one or two Shohin displays. This way each discussion is more in depth and the value add is much more than just a walk through the exhibition and barely spending a minute or two with each tree. What I would like to see is that when it comes to multi-day shows, that the Critique is extended and broken up over more sessions across all days. This can be thematic i.e. each session focusses on only one style of tree (design) or split the trees in Evergreens and Deciduous trees or as mentioned above, do the Shohin separately. The main things is that there must be something new to learn for every participant and the owner needs to walk away with a feeling of accomplishment and also a few pointers on next steps for the tree.

This is the Robert Steven book referred to above.

Weeping Bonsai Trees – NZBA Convention Demonstration and Talk

I was asked to demonstrate at the recent 2019 New Zealand Bonsai Association National Show and Convention. I decided to talk about Weeping or Pendulant trees as these trees are quite scarce in New Zealand at show level. There was only one weeping style tree in the National Show, a native Kowhai tree.

The interesting thing is that many people spoke to me afterwards to tell me about their weeping Bonsai trees and even about going to have another look at taking cuttings from Willow trees, probably the easiest of trees for this style.

Below is a video of the presentation that I used. I started off by talking about the biochemistry and the role of geotropism (movement or growth caused by gravity) and the effect of that on auxins in the tree to allow branches to grow downwards. Next was a few slides of weeping trees in nature to show the most important principle of building an upwards growing structure first before you look at the weeping parts of the tree. This was followed by slides of relatively well-developed weeping style Bonsai trees.

I also showed a Willow tree from a cutting, a nursery sourced weeping Beech tree and another nursery sourced weeping Bottlebrush. I talked about wiring the main structure and then also the use of guy wires and objects to hang off the branches to pull the branches downwards. It also included examples of fishing line with weights attached and even the humble clothing peg to act as weight to help gravity do its thing.