Image via Wikipedia

The thought of root pruning fills most bonsai novices with horror, but it is essential in order to maintain the tree’s health and vigor. If the process is ignored your bonsai will become pot bound. It will weaken, shed shoots and branches and eventually die.

In the wild a tree will extend its roots each growing season in much the same way as it produces new shoots. These new roots do most of the work, absorbing water and nutrients. As the tree matures some older roots will die back, only to be replaced by strong, new ones.

However, things are different in a pot. You have to reproduce this cycle artificially in order to keep your bonsai healthy. Health means vigor, and a vigorous tree is more able to resist disease and can outgrow attacks by pests. It will also respond better to training techniques.

A healthy young bonsai - say up to ten years old - in a small pot will pack its container with roots within one season, so it will need to be root pruned each year. Older trees, especially conifers, tend to grow more slowly, taking perhaps ‘up to five years to fill the pot. However, before you start to panic, remember that it takes time for problems associated with root confinement to take effect, and you can miss a year every so often without putting your tree at risk.

Just as the roots begin to grow in spring is the ideal time for root pruning. Although it is possible to repot at any time during the dormant season, the longer the wounds wait before they can regenerate.

The exact timing depends on the advancement of the season, geographical location and the species. Deciduous trees, particularly trident maples and elms, start producing new roots early as mid-February in the south of England but not until a month later in the north. Pines may not start new root growth in earnest until April in the south and as late as May further birth.

The first sign of root activity is a slight swelling of the buds on last year’s shoots. You can check further by gently lifting the tree from its pot and taking a close look at the roots. If the tips appear to be swelling the time is right. If the tips are white they have already started to grow, but pruning will do them no harm so long as the new buds have not opened yet.

If, on the other hand, your tree is due for repotting in theory and the buds have begun to swell but the visible roots appear brown and dead, this may be an indication of decay. As often as not, lack of vigor, wilting or premature leaf-fall is a symptom of a root-related problem such as decay or attack by the voracious vine weevil larva

Image by Carl_C via Flickr

This is the ultimate refinement technique which is only suitable for broadleaved deciduous species. It results in a very fine, compact twig formation, tiny leaves and enhanced autumn color in the year it is applied. Leaf pruning can also be employed as a device for reducing transpiration after emergency out-of-season repotting.

Since this technique causes a certain amount of stress to the tree it should only be carried out every three years or so, and only on trees which are in good health and vigour. For this reason its use is normally restricted to bonsai which arc in preparation for exhibition. The ideal time for leaf pruning is early summer, as soon as the spring growth has hardened.

The principle is similar to shoot pruning and pinching, in that the reduction of foliage encourages new side growth to take place. But because the foliage is totally removed the tree undergoes a ‘false autumn’ and next year’s growth develops this year. This means that there will be a much greater nunifier of new shoots than existed before, bearing correspondingly more leaves.

Since the tree can only support - and only requires - a fixed volume of foliage, these leaves will be greatly reduced in size. Also, since these leaves only have half a season to live they will be in better condition come autumn, resulting in brighter colour over a longer period.

Image by vigilant20 via Flickr

Once the branch structure has become established there should be enough new shoots appearing each spring, bearing sufficient foliage to sustain the tree without necessarily allowing any extension growth. Extension growth draws the energy from the rest of the tree, concentrating it in the growing tips. This starves the fine inner twigs of nutrients and the additional foliage prevents them gaining adequate light. The result is that the fine twigs die and the whole twig development process will need to be started all over again.

First we have to build and refine this tracery of fine twigs. Once this has been done the resulting foliage pads must he kept trimmed and in balance with the design. Both of these ends are achieved by pinching out the tips of all new growth as it appears.

Different species grow in different ways, and the following techniques have been developed to accommodate the five most common growth patterns.

• With broadleaved trees new shoots will emerge from. the buds in the remaining leaf axils.

• In pines new buds will form at the point at which the shoot is pinched, as well as further hack on older growth.

• Larch and spruce will only produce new shoots from buds which are already visible on the remaining shoot or from around the base of the shoot and on older growth.

• Jumpers will throw out new growth from any branch or shoot which bears foliage, and need constant pinching throughout the growing season.

Image by jcolman via Flickr

Each year your bonsai will throw out new shoots from the buds created in the leaf axils during the previous growing season. It will only take a few weeks for these shoots to outgrow the design of the tree and make it look very scruffy.

In a developing or semi-mature bonsai these shoots can be allowed to grow to six. or seven leaves before they are cut back. Allowing them this period of free growth thickens the parent branches and trunk and builds up a general vigor in the tree. If allowed to grow too long they will sap the strength from the finer growth and will quickly kill it off. New shoots will emerge from the buds in the remaining leaf axils. Any wayward shoots, or those which are destined to become new branches, should be wired at this stage.

However, in established bonsai this annual growth will need to be cut back during the dormant season to allow the next season’s growth room to extend before outgrowing the design. Over the seasons this constant `clip-and-grow’ technique will reward you with a much-forked branch structure, with all the characteristics of an ancient tree.

Always remember to prune to a bud which points in the direction you want the new growth to take. It is possible to style a bonsai entirely by pruning if you have the patience.

The best time to do your winter pruning is late in the season, before the buds swell hut after the worst of the weather is over. The setback to the tree caused by pruning off fattening buds is slight. But prolonged periods of frost could do severe damage to a newly-pruned bonsai.

Image via Wikipedia

When a branch is pruned it will inevitably leave a scan With full- sized trees the wound will normally heal rapidly and any resulting disfiguration will be of little or no consequence.

However, since bonsai grow more slowly the healing process is slower as well, so it needs all the help it can get. Also great care must be taken to minimize the possibility of unsightly swellings around the wound, and to encourage the scar to blend in with the character of the trunk.

The first technique shows you how to execute simple pruning, where a small to medium sized branch is removed. The second shows how to use a larger wound to your advantage, by hollowing it out and turning it into an interesting feature.

Here are a few general points to bear in mind:

• Always use very sharp tools, which should ideally be sterilized by immersing them in methylated spirit for a few minutes. This is especially important when pruning away diseased wood.

• The cambium layer (between the bark and the heartwood) must be sealed against frost, water and drying wind. If left exposed it may die back, increasing the size of the wound and delaying the healing process.

• Never use horticultural bitumen-based sealants. These will dry hard and will be impossible to remove from the surrounding bark without causing disfiguration.

• Feed the tree well after drastic pruning to speed up the healing process. The more vigorous the tree, the quicker it will heal.

Image via Wikipedia

A bonsai pot is more than just a container for the plant to grow in. it as an integral part of the composition and must complement the tree to form a harmonious unit. Here we show you a selection of different types of pot and indicate what styles or species they best suit.

As well as the aesthetic considerations the pot also has to satisfy some practical requirements, so the following tips should be remembered when buying pots:

Ensure the pot is stoneware, which is frost-proof, as opposed to earthenware, which is not. Earthenware pots will rapidly disintegrate with the first hard frost. A simple test is to wet the unglazed surface of the pot to see if it absorbs the water. If it does it is earthenware, if the water wipes off cleanly the pot is stoneware.

There must be excellent drainage. The holes should be at least three times greater in number and size than in a conventional flower pot.

The floor of the pot must be level, so that no pockets of water can accumulate in the base. Check that there are no indentations in the corners where the feet are fixed.

All pots must have feet in order to leave space for the drained water to flow away.

Avoid pots which are glazed on the inside. This provides an inhospitable surface for the roots and will cause the soil to dry out too quickly around the perimeter of the pot.

A number of nurseries now sell pots made of mica, which retail at less than half the price of stoneware pots. These look authentic, and are ideal for temporary or training pots, but the surface scratches easily, so they are unsuitable for exhibiting.

Image via Wikipedia

Most plants will survive in limited periods in almost any growing medium clay, sand, even pole water - but in order to thrive they need rather more. Since bonsai are grown in shallow containers for many years their requirements arc quite specific.

The soil’s most obvious function is to retain enough moisture and nutrients to ensure a steady supply to the roots between watering.

The soil must protect the roots from decay by allowing the tree drainage of excess water.

It must also contain air spaces so the roots can breathe.

Finally, the soil anchors the tree in its pot, so it should not be too light.

The standard bonsai soil recipe, which has been tried and tested for many years, contains just two ingredients which, when sifted and mixed in roughly equal proportions, satisfy these four basic requirements.

All soil ingredients must be well sifted to remove all the coarse lumps and, snore importantly, all the fine particles. Ideally you should he left with particles ranging in size between 2 and 4mm. If there are any particles finer than this, it may be difficult to wet once they are dry out. They will also clog the soil, impeding drainage and eliminating air spaces. To sift ingredients efficiently make sure they are fairly dry.

Organic matter satisfies the first of the tour requirements mentioned above. This can he moss peat (as opposed to sedge peat), well-rotted leaf mould, composted forest bark or any of the peat substitutes which are becoming increasingly common.

Don’t use any farmyard manure or garden compost, however well rotted, as you will risk introducing all manner of soil-borne diseases.

If you collect your own leaf mould remove any rotten material which will use up nitrogen from the fertilizer it continues to decay.

Also remove any insects or grubs that you may find. Some people sterilize leaf mould by placing it in a microwave oven for a few minutes. Oak, beech, chestnut and pine leaves produce the best texture.

Flint gilt, as used for alpine composts, is good but it has sharp edges which can damage the roots if used carelessly. So be gentle when repotting and don’t use too much pressure.

By far the best type I have tried is granite grit. The surface of each particle is uneven, but the edges are not sharp. Grit from fast-flowing streams is also good. Whatever kind of grit you use is not terribly important, however, so long as it is included.

An increasing number of soil conditioners are available to the amateur gardener, ranging from volcanic lava to calcined (baked) clay. The main advantage of using such additives is that they perform the same functions as both organic. matter and grit. That is to say they drain well but also retain moisture. Some growers use calcined clay instead of organic matter, and others find trees grown in pure lava do exceptionally well. It is always worth experimenting.

Any bonsai nurseries now sell imported Japanese Akadama clay, which is specifically produced for bonsai. It retains its granular structure when wet, drains freely, retains moisture and air and allows the roots to grow through the particles. It sounds ideal, and indeed is in Japan, where the climate is predictable. But in our climate you may need to water your trees more often in summer, and keep them out of excessive rain during autumn and winter. However, it is worth trying.

If you feed your bonsai properly it is not necessary to add fertilizer to the soil, but it does no harm to include a little bone meal or fish, blood and bone. Acid some trace element compound as a matter of course, since none of the ingredients can provide their own.

Image via Wikipedia

All you really need in the way of equipment for your first attempts at growing bonsai are those which you probably already have.

- A pair of sharp scissors

- Wire cutters

- Secateurs (the bypass type, not the anvil variety)

- Nail scissors for fine work

- A pointed steel hook for combing out roots.

These tools will do the job almost as well as the specialist Japanese tools. But as you gain experience you will begin to find them a little clumsy at best and totally inadequate at worst. Sooner or later you will want to invest in your first proper bonsai tools, but rather than spend a lot of money on a full set, buy them one or two at a time.

Because they arc the cheapest tools you will probably decide to buy a couple of pairs of scissors first, long ones for trimming and short shears for heavier work such as root pruning. This is a good choice and you will soon discover how easy the Japanese tools are to use.

Next you should go for some side cutters which can cut branches cleanly and accurately, and some long-handled wire cutters, designed to cut right up to the tip. The big advantage of both these tools is that they are able to reach the most inaccessible parts of the tree.

Curved branch cutters should come next. These are used for pruning close to the trunk, where a slight hollow is required to help the wound heal over quickly. Some bonsai pliers would be a good idea too. The shape of the jaws makes them ideal for stripping jins and sharis, as well as for manipulating the wire once it has been applied to the tree.

Image by tantk99 via Flickr

Sonic people prefer to grow very large bonsai but are unable to find suitable raw material growing in open ground, and are unwilling to spend the required number of years to grow their own. The only alternative is to acquire a suitable plant from a tree nursery. These trees are intended for planting in parks, streets or large gardens and are grown in the ground for a number of years before being established in containers prior to sale.

When seeking out such material make sure it is well established in its container; moss and weeds growing in the soil is a good indication of this. Examine the surface roots to ensure they are evenly distributed. Scratch away a sliver of bark on each one - if it appears green beneath the bark the root is alive, if it appears brown or grey the root is dead.

Cutting off the top section of the trunk will force a tree to throw out shoots from the remaining trunk, but their location cannot be predicted and there is every chance that they will he limited to the area immediately around the cut. This is useless for bonsai purposes unless you intend to grow a broom.-style zelkova. So you will need to counter this by selecting a. plant which has a good number of low branches.

You can carry out this initial pruning any time between November and the following June, but the ideal time is in early spring, just before the buds break.

Leave the tree in its original container for at least a year before attempting to plant it in a bonsai pot. During this time too can begin to style it by wiring and priming.

Image by ashleytheartist2002 via Flickr

Two of the most desirable features in any bonsai are mature bark and pronounced taper of the trunk. These properties are always difficult, and often impossible, to achieve when a tree has spent all its life growing slowly in the confines of a shallow bonsai pot.

Traditionally, the most revered specimens were created from stunted plants collected from the mountains of Japan. But nowadays, to do this would he highly irresponsible almost anywhere in the world and certainly illegal in most western countries.

The only satisfactory solution is to grow your own raw material in a way which produces all the desirable characteristics in as short a time as possible. To do this you need to encourage the lower branches to grow In order to thicken the lower part of the trunk. If the base of the trunk is mulched with straw or leaf mould the bark will swell and crack, making it kink look even older.

The result is a heavy trunk with considerable taper, flaky bark and many old scars - all the characteristics of great age.

This technique of growing raw material is ideal for most deciduous species, but not suitable for conifers since they will not regenerate growth once all the foliage-bearing branches have been removed.

When growing conifers in open ground prune back as hard as you can every two years, while still leaving some foliage on each branch. Each spring pinch out about half of every new ‘candle’ as soon as they are big enough to handle. This will produce masses of branches and shoots to choose from when you eventually come to style the tree.