Pruning refers to the removal of branches that are usually too thick to be removed with scissors. This is not always the case in very small trees but works as a general idea of what tool to use when. Pruning is usually carried out in the winter when sap flow has all but stopped. Cuts should be sealed to prevent drying out of the wound. Japanese sealants come in two forms, a silicon based wound sealant that comes in a tube that is used for sealing od small cuts and cut paste that is a putty material that is used to seal larger wounds and the edges of jins and sharis. Both are best applied liberally as thiclk layers are easier to remove at a later date.
Most deciduous trees need to be sealed after pruning but many sappy trees such as pine, larch, spruce and fig will seal themselves. Any additional sealing only makes more of a mess.
Pinching is carried out on most species when the new growth is still very soft. It is done on deciduous and coniferous species with the intention of inducing back-budding in order to create more branches to grow before the space between leaves becomes too great. As its name suggests pinching is done with finger and thumb, usually with the fleshy parts. If finger nails need to be used then scissors would be a better option. Pinching is most effective on coniferous species, especially Juniper and Spruce in order to form closely bunched pads of foliage. It is carried out in spring and early summer. Pine is also pinched but since pines respond in different ways to different amounts of shoot removal, it would be foolish to attempt to generalise. (See Pines for more details)
By trimming I mean the removal of fairly new growth that has not has not yet hardened off but is too thick to pinch off. The obvious question here is "Why let growth get too long in the first place?" The simple answer is that some trees, notably Chinese Elm need to put on some growth so that the dormant buds at the base end of the branch have time to form. Removing the growth sooner will not produce back budding and will more than likely result in a dormant branch that will probably die back in the winter. This does not apply in all cases. Maples for instance are pinched back as soon as two leaves have appeared as the new buds have already formed in the leaf axils. Check the species guide for your trees requirements. If it is not covered it means I've not had time to write it yet but feel free to e-mail me.
Root pruning is the process by which we allow a tree to remain in a pot of a given size without it becoming root-bound. It is usually only carried out once a year at most, just before growth begins. It can be compared to the trimming and pinching above ground in that it has much the same effect. When a root is cut, the new growth will divide into two smaller, finer roots. Common-sense is the most important factor in carrying out this operation. Never root-prune a tree that looks sick unless you are certain that the problem lies in the roots themselves. Never leave a trees roots exposed to the elements for longer than you have to. Prepare the pot and mix the soil before working on the tree so that it can return to its home as quickly as possible. Having said that, don't be tempted to rush the job and just give the roots a quick trim.Comb out the roots carefully. Cut back any thicker roots that have little or no fine roots coming from them and remove any roots that are growing downwards from below the trunk. The aim is to achieve a system of fine roots radiating out from the base of the trunk. You'll know a good root system when you see one because it will have a beauty all its own.
Defoliation
Defoliation is a technique carried out on certain deciduous species, notably maples, to induce a second flush of leaves usually prior to showing. Removing all the leaves from a tree makes it think that it is spring all over again. It will produce a new, hopefully more plentiful supply of buds that will result in a balanced set of smaller leaves. This technique is not recommended for beginners. The timing is crucial and it should not be attempted on a tree that has been re-potted in the same year and should not be done every year. Some would argue that it does a tree good and creates vigour but this is often mistaken for the trees desperate fight for survival. Approach with care and seek expert advice if unsure.
Fertilisers can be broadly split into two types. Chemical and Organic. Chemical simply means man-made and organic signifies that the contents are of a natural origin such as blood, fish and bone or rape seed. The common link between them is the way that all fertilisers are classified in terms of their content of three vital ingredients. They are Nitrogen, Phosphorus and Potassium. This is referred to as the N:P:K ratio and appears on the side of the box as, for example 10:10:10. This ratio also gives an idea of the concentration when mixed to manufacturers recommendations. A ratio of 20:20:20 would be twice as strong. These are examples of balanced fertilisers, i.e. they have roughly equal amounts of each component in the mixture. Bonsai, because they are confined in a pot with varying levels of water and sometimes inadequate drainage, are best fed with a weaker dose than recommended.
I use Naruko 5-5-5 pellets or Bio Gold organic pellets as a general feeding regime and give extra weak liquid feeds in specific cases to trees with special requirements.
High Nitrogen feeds have their uses in promoting lots of growth in trees that are being grown on but beware of feeding to established trees as this will result in unwanted bushy growth. Proprietary Bonsai food is basically the same formula but a look at the ratio will reveal a weaker mixture that should be used at full strength. A ratio of 5:5:5 at full strength or 10:10:10 at half-strength or even 20:20:20 at quarter strength will work in exactly the same way.
Acid loving species such as Azaleas will need topping up with an ericaceous fertiliser to maintain the acid pH and iron levels.
Little and often is far better than a lot now and again. There is an argument for feeding every time you water with a much weakened solution. On the one hand trees will get fed in direct proportion to the amount of water being used. On the down side it is difficult to know what strength to use and to keep track of how much the trees are actually getting. If you have a lot of trees that are watered by hose-pipe then the logistics of the exercise also come into question.
Granular or pellet feeding overcomes this problem as they sit on the soil surface and slowly release feed. Traditional fish paste or rape seed feed cakes have problems with odour, maggots and fungus but the newer products such as Naruko and Bio Gold claim to avoid this.
In the Autumn when new growth needs to be hardened off before winter, I use tomato food or Chempak 0:10:10. The low nitrogen content stops fresh growth and the concentration of P and K help in hardening off.
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