GREEN_DRAGON_BONSAI

Repotting
It is advisable to seek advice when repotting for the first time and if possible get someone who knows what they are doing to demonstrate the process. Not everyone has access to such luxuries so this article will take you through the steps involved and hopefully make the fairly straightforward yet daunting process a little easier.

Why repot - Bonsai need to be repotted in order to create growing room in the pot. A healthy root system is one that has room to expand slightly. For our purposes we need to create a fine root system. In trimming branches we seek to create a nicely branching structure dividing repeatedly from a thick branch down to delicate buds. The same applies to the root system. The thick roots at the base of the trunk are needed for visual effect but once hidden under ground the subdivisions can begin in order to create as many fine roots as possible. The amount of root that you remove when repotting will reflect many things. The trees health should be considered first and foremost. If your tree has been off colour for a while then it is likely to be incorrect care that is causing the problem. Removing large amounts of a root system that is already struggling to maintain the tree will only make the problem worse. In such cases repotting should be considered as a last resort.
For healthy trees, the size of pot should be the next consideration. From a health point of view the pot needs to be large enough to allow a seasons growth. If enough root cannot be removed safely to allow this in the existing pot then consider moving to a slightly larger pot. This is quite common especially with younger trees that will naturally want to get bigger and whose vigour demands slightly more growing room.
Pots are often chosen for artistic reasons and trees placed off centre for aesthetic reasons. If moving a tree to a pot where it will be off centre, the amount of roots on one side will probably need to be reduced. If this means that the roots will be very close to the side of the pot, moving to a slightly larger pot will create the same effect whilst still allowing a little growing room. Older and slower growing species will not need repotting every year so assess whether it is totally necessary.

What you may need

Soil mixture - You will have read the relevant articles on soil mixtures and will have whatever mixture you are going to use to hand. The mix should be fairly dry and you should make sure that you have enough.
Potting Mesh - to cover the drainage holes to prevent soil falling out and to deter large insects from getting into the pot
Wire - In most cases the root ball should be securely fastened into the pot. Use Aluminium or copper wire for this and also to make hold the mesh in place.
Root Pruning Scissors - It is a good idea to have a separate pair of scissors with sturdy blades just for root work. Fine trimming scissors will soon be damaged in cutting through roots that are caked in dirt and bits of grit.
Root Hook - Custom made root hooks are ideal for the job of teasing out the root ball but chopsticks and knitting needles can also be used.

Plastic bag - If you are planning on reusing the same pot, have something handy to wrap around the root ball while you prepare the pot

Ok so lets have a look at a practical example step by step.
Here we have a mountain Maple that is showing promise. I t has the mother of all pruning scars running up the back of the trunk but from the front and especially with leaves on it is not obvious. It was last repotted 12 months ago and will need repotting again this year not only because the roots have fille dthe pot but also becausethe position in the pot is not right. The visual weight of the tree is slightly towards the right and it is leanig forward slightly too much. It needs to be tilted back slightly and repositioned slightly off centre to the left.

We'll start with a bit of cleaning. The pot market is awash now with some lovely chinese pots that are excellent value for money but do have a tendency to leech salts out of the clay. I am using a steel scourer to remove the deposits. This is also the time to clean the moss from the trunk and do a bit of weeding while everything is rock steady in the pot.

Next we need to get the tree out of the pot. In most case this is simply a cse of cutting any securing wires and lifting it out. However id the pot has a slight lip as in this case the edges will have to be loosened using a root hook, or if need be a knife or in severe cases a folding saw.

Here you can see the scar at the back that you would never had guessed was there if I hadn't mentioned it. This shows that not everything has to be perfect and also acts as a cautionary note when buying trees from photographs.

Right there we have it free of the pot. You can see how the roots have grown round the base of the rootball. Note the use of an upturned plant pot, no expense spared here.
If you are going to be a while with the next step, bag up the rootball to stop it drying out while we look at the pot. Add or replace the mesh and secure with wire twisted into a figure eight with tails. Also add new wires for securing the tree. If you don't have the proper wire holes, use the drainage holes.

As a rough guide you should be looking to comb out about half the distance between the edge and the trunk. Work on the sides all the way around and then examine the roots for any major changes that need to be made. In this case there are a few points that need addressing.

This is a close up of the front edge that highlights the sort of things that need sorting before they become a problem for the future.

A. The root on the left is quite thick and uniform in thickness. It has a long bare section with a cluster of fibrous root at the end. If left unattended the cluster will only get thicker and there is little chance that new roots will emerge from the bare section.
A side root at A is well formed and thinner than the rest so the big root can be cut back to there.

B The crossing roots are undesirable. The thicker one can be removed

C. The root on the left is very thick and unsightly. Below it there are several thinner roots that will function better in the future.

The left root was cut back to the side root

The centre root was removed all the way back to the base as neither of the crossing roots amounted to much and were contributing little or nothing horticulturally or visually

The right hand thick root was removed in favour of those beneath

The result may seem a little drastic to the uninitiated but this is the kind of bold steps that must be carried out in order to create a workable rootball for the future. Bear in mind that in each case no roots were removed without first ensuring that there were better or equally viable roots to continue the supply of nutrients to the tree.

Back at the main task in hand the sides of the rotball are trimmed all the way round. The amount to remove should be somewhere beteen one third and hal the distance from the old edge to the trunk In this case just under a half was removed because this was the best position to create some interesting sub divisions on the left hand side roots. Also this tree was repotted last year in a similar fashion so is trimmed not quite as far back as last year in order to make the most of the branching of the roots that has occurred in the previous year.

A well maintained root ball will produce little growth on the underside so it is just a case of removing the loose soil and trimming the straggly bits

Time to get our tree back in its pot.
Make a mound of potting micture in the centre of the pot. I am using green dragon mix here, a mix of equal parts Akadama, Kyodama and cat litter.Read all about it here. Jiggle the tree on the mound to get the desired position and height. Then secure with the wires.

Introduce the fresh soil around the roots working it bewtween the roots with a chopstick or knitting needle. The idea is to allow the soil to flow between the roots and any compaction should be avoided and a nice loose soil mix will provide better conditions for re-growth of the roots.

Fill the pot and then add moss to cover the holding wires. Give your newly potted tree a good soaking to bed everything down and wash away any dusty particles in the soil mix. Protect from frost The exposed root ends will be sensitive to the cold for a while so frost protection is a must. Do not feed for six weeks. There are several schools of thought on this point but traditional policy dictates avoidance of feeding while the tender new roots are sprouting and resume feeding gradually with a weaker than usual dose of fertiliser.
Common sense
Every tree is different. While this procedure is a good basis you will encounter the occasional dilemma. Field grown trees that have been cultivated especially for the hobby will have had some work done on the roots and the system will be fairly compact. Others, particularly large collected trees have not been told that there ultimate destiny is life in a pot and have happily produced a root system in preparation for life in the wild. Cases like this will need a common sense approach where the needs of the tree must be placed first in order to keep it alive. There is no point rushing and cutting off too much root in order to get a tree into a pot. Re potting must be approached in stages sometimes over a number of years in order to train the tree to grow the correct type of roots in abundance. Remember - if in doubt, ask

Unfortunately the heavens had opened and a hurried snapshot of the final result will have to suffice for now

WHAT IS BONSAI? - A brief introduction defining Bonsai

GETTING STARTED - A few simple pointers to get you going

TOOLS AND TECHNIQUES - An outline of the basic requirements

THE CHINESE ELM - Everybody starts here, some home truths

FREQUENTLY ASKED QUESTIONS - A whimsical look at some common problems

BONSAI CALENDAR - What to do and when to do it

STYLING - DEVELOPING THE EYE - Slightly more advanced but essential

5 MINUTE RAFT PLANTING - A simple project

THE ILLUSION OF BONSAI - More food for thought

BONSAI SOIL - A look at the essential of mixing a good Bonsai potting medium

BONSAI FEED - An overview of feeding practices to get you thinking

LINKS TO OTHER SITES

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