Article 54 – ‘Summer pruning’

Introduction – The pruning of a bonsai tree is probably the most important single factor in the forming of its shape, perhaps more so with deciduous than with conifers due to their rather intensive growth. Pruning as such can be divided into four main headings, Root, Heavy branch, General and Leaf. When pruning roots and foliage it is often stipulated that what percentage removed from the roots should be reflected in the foliage and visa versa, because this reduces stress maintaining a balance between the tree’s two sections.

Nonetheless, there are those who disagree they contend that some deciduous species can have their foliage completely removed in the growing season to encourage new growth. This Ginkgo biloba spends the colder months (October to May) inside under LED grow lights with a constant temperature of 24 degrees C. Complete leaf drop occurs when it goes from inside to outside (late May) but, within 4-5 weeks it is back in leaf. This situation repeats itself when it is returned indoors, (mid September) thus the tree loses its foliage twice in a relatively short space of time; an 8 to 10 week period of no foliage, which does not effect the tree’s health. The reason why leaf drop occurs twice is due to environmental change – not the plant entering dormancy.

Ginkgo biloba

To further this discussion a Himalayan juniper Juniperus squamata was obtained in early spring 2021, according to the fact sheet this plant should be located where it receives full sun; a minimum of 5 to 6 hours per day. We decided to experiment by adopting a different approach, a round Japanese bonsai pot was selected, but as the tree had a large root ball, 60% of it was cut away in order for it to fit the pot – none of the foliage was pruned resulting in an imbalance between root and foliage. The plant was then placed in a location that has full shade and as the image shows, the plant is thriving with no ill effects; this juniper will be left for a few years before styling begins.

Himalayan juniper J. squamata

The argument of maintaining an equal balance between root and foliage has theoretical logic and in many cases may prove to be correct with certain species of plant but, as we have demonstrated here there are instances where such logic does not apply nevertheless, debates on this subject will no doubt continue.

Root pruning – is carried out periodically because bonsai grow in small containers. Such confinement forces the root system to encircle the entire pot area saturating it in a dense mass, the result is the plant becomes ‘pot bound’. In this situation it begins to suffer because the much needed nutrients have been exhausted, circulation of air in the root mass is restricted and watering retention is increased. Deciduous species can be rigorous in their growth, hence it is prudent every 2 to 3 years to lift the plant out of the pot to check the roots ball’s condition whereas, coniferous species can be checked every 5 to 6 years, but much depends on the species and variety.

Foliage pruning – In 2017 we acquired a common juniper Juniperus communis which was trained as a cascade, (Kengai) it was left to grow and conform to its new design until July 2021 when pruning was much needed as the cascade appearance was masked by excessive growth. Branches had intertwined and were invisible, foliage was dense creating a hiding place for unwanted minibeasts moreover, it restricted air flow. Below are two images of this plant – before and after.

Juniperus commnunis cascade (Kengai)

As one can note there is a marked difference in this tree’s appearance and arguably there is improvement, but there is a lot more work to be done pruning wise. In addition, those with a keen eye will notice that this tree lacks a ‘top knot’ or crown, the original 3 branches at the top succumbed to the 2017 winter period and were later given a Jin or shari look. However, there is a small shoot protruding out from underneath the upper most bend that hopefully will replace those that were lost.

The next plant to be given hard pruning is this Sea Buckthorn Hippophae rhamnoides being trained in a Literati or Bunjin style. In the left image the foliage is masking the branches of which there are 3 as shown in the right image with the top one the main branch. This branch when dormancy arrives will be wired into shape and allowed to extend further down towards the container, the other two branches will probably be reduced and wired into new positions; and the ‘top knot’ will be allowed to develop. This Sea Buckthorn is only a young tree, (6 years old) but has the potential to become a Bunjin.

Sea Buckthorn Hippophae rhamnoides

Pruning in generalHeavy Branch Pruning – with trees obtained from nursery sources or from the wild, pruning can be carried out immediately however, with established trees waiting till the autumn to prune is more convenient as the form or shape of the tree, especially with deciduous varieties, can be visualized more easily.

The rules for initial heavy branch pruning are not written in stone, they are more of a guideline. Having decided what the material or plant’s potential may be, one can start work. But before brandishing the shears, a good tip that some bonsai enthusiasts undertake, is to either (a) take a photograph, which can be downloaded to a computer where the style can be enhanced via a suitable program, or (b) draw a sketch of the plant; doing this allows you to finalise the design.

The ‘hand drawn’ image below shows a plant selected to be grown as an informal upright. (Moyogi) Working from the bottom of the tree, a low branch protruding at the front has been removed, as has the opposing branch above it. Further up, the tree has developed a cartwheel effect meaning that more than two branches appear at the same height on the tree; in this case two branches were removed. At the top, the branch on the right had possibly been damaged at some time and rather continuing to grow to the right, had grown across the front of the tree and this was removed. The illustration shows the effect of this initial pruning.

Heavy branch pruning

Different styles of bonsai require different forms of heavy pruning, as a general rule dead, damaged, or diseased branches are removed. But with conifers such branches are formed into Jins or Shari, which gives the tree a more aged-look. Jins and Shari are branches that have been stripped of their bark and cambium layer then coated in lime sulphur, which bleaches the branch. With heavy pruning, there will be wounds and these are susceptible to disease, some bonsai enthusiasts advocate the use of expensive cut pastes to seal the wounds, some use petroleum jelly (Vaseline) a fraction of the cost; whilst others do nothing allowing the tree’s natural defences to heal itself.

General Pruning – is carried out throughout the growing season and with most varieties it begins almost immediately they begin putting on the new season’s growth. New growth of all trees can be pinched or removed with the fingers, but if a tree is left until this growth has begun to lignify or harden off, then sharp shears will be required. Pruning is done to maintain and improve the shape and symmetry of the tree and ramification, it is also necessary for the tree’s health.

Leaf pruning

Leaf pruning – is a method of increasing leaf coverage and fine twig-lets it also assists in reducing leaf size, but it should only be carried out on trees that are healthy and are growing strongly; in some cases more mature trees are less vigorous in their growth for this treatment. June (Depending on the climate zone) is the time when all the leaves except for the petiole (leaf stalk) are removed and after a period of time, approximately 2 to 3 weeks, new leaves and branches will form. However, it should be noted that leaf removal is restricted to deciduous trees, never with conifers, flowering or trees bearing fruit. The above illustration shows how leaf pruning is carried out on pines, junipers, maples and zelkova. (N.B. if you wish to contact us email information is in the ‘about’ section.) Until next time, BW, Nik.

Article 53 – ‘Superglue, tape or beeswax?’

Introduction – Plants prone to the elements can suffer great damage with arguably storms, high winds and excessive snow build up being the worst offenders. Trees can be uprooted and/or have the branches break off and in the case of the Birch, (Betula pubescens) large amounts of snow accumulated at the crown can bend the trunk down into a permanent position, from where it cannot recover; the forests of Scandinavia have many trees that have been devastated in this way.

Bent birch (Betula pubescens) courtesy of dreamstime.com

However, such damage is not solely confined to the wild, domestic plants including fruit trees and bonsai are also prone to the onslaught, a severe wind can lift a bonsai out of it’s container if not wired in or send crashing to the floor. But much depends on the individual situation the weather patterns of the zone in which one resides and the amount of protection available. If damage is caused, how then do we repair it and with what?

Various methods – In the article ‘Wiring practices part II A’ February 12th 2019 one of the topics on severe bending and shaping included Heat – using a heat gun or gas burner to soften the cellular structure on the intended area. Splitting – cutting the branch in two halves and reducing the heart wood, these are then joined together and the bend is made. Channelling or grooving – cutting a groove or channel into the branch to remove the heart wood, thus resistance is reduced allowing the branch to be shaped.

Another simpler method when bending branches is the ‘V’ notching technique as shown below: Small angle cuts A, B & C an inverted ‘V’ are made in the branch into the heart wood but not beyond, these ‘V’ cuts are then closed as the branch is bent down using guy wires attached to the container preferably wooden. These surgical practices severely wound the plant hence, much after care is required in maintaining the tree’s health and eradicate potential disease caused by pathogens that are small, an ultramicroscopic with one dimension less than 200 µm. (the symbol µm is a metric unit of measure for length equal to 0.001 mm, or about 0.000039 inch)

‘V’ notching technique

Super glue – As we are aware surgical super glue (cyanoacrylate adhesive) is often used on people with cuts or lacerations as opposed to stitching depending on the severity of the wound, but could it be used to repair a tree? The tree and branches are predominantly round in shape with the xylem shown below consisting of two important cellular channels the sapwood (grey with pale blue dots) and the phloem (green with white dots) that transport nutrients to the leaves and sugars to the roots respectively.

If a branch is broken away from the trunk chances are it will be a clean break, hence it might be possible to super glue the branch and broken limb back in place, but take care not to let any glue touch the phloem as this can create a barrier restricting sugars from reaching the roots. In addition, although the bark will be dry, the cortex is moist so whether the repair will be successful remains to be seen. Moreover, to ensure that the repair holds an application of super glue around the damaged area needs to be applied as this will seal the joint and protect it from fugal attack.

Tape – Many horticulturists advocate the use of different types of tape including old bicycle inner tubes as it adds strength and stability to the damaged area and can be left in situ for long periods of time or until the wound has healed. Those who use Splitting, Channelling, Grooving and ‘V’ notching techniques also use tape, but the question is, has the wound been completely reassembled and sealed, It only takes the smallest of unprotected areas to allow an attack from pathogens.

Beeswax – (Cera alba) a natural wax produced by honey bees of the genus Apis and has many uses for example, In foods and beverages, as stiffening agents in cosmetics, a fragrance in soaps, perfumes and the protection of antique furniture. Beeswax can also be melted and used as a protective layer in preventing infections. Some fruit growers whose tree branches have been damaged by the elements, carefully attach the limb back in place and use melted beeswax to seal and secure the join.

Pros and Cons – The question here is which method is the best? – super glue (cyanoacrylate adhesive) does work, two years ago the first finger of my left hand was severely lacerated and was treated with this method and healed relatively quickly. Tape is strong and stable but can be fastidious and fussy especially where branches are broken next to a protruding limb moreover, any buds that are taped will not be able to break. Melted beeswax applied to the wounded area when solidified becomes a protective sealant allowing the repaired branch to function normally, it is also used to protect areas where grafting has taken place.

As to which method is best depends on where the break and it’s severity has occurred as both the phloem and sap wood need to be able to function pass the damaged area. However, as stated above branches regardless of their thickness or size are predominantly round and the phloem and sap wood are continuous in their circular positions within the xylem and are able to function even if damaged. Trees have the remarkable ability to heal themselves even if limbs are lost and some species are able to produce new growth from their roots. Arguably an experiment should be performed to substantiate this theory, which will happen in due course when a suitable candidate/s is found; until next time, BW, Nik.