Repotting Bonsais

Certain guidelines need to be followed while repotting bonsai trees. For instance, superior quality compost is indispensable, as it directly affects the bonsai's health. However, experts differ on the composition of good quality compost. However, generally, a bonsai will thrive well when grown in compost prepared by blending equal amounts of superior quality loam, peat and either decomposed turf or sand. A number of plants, for instance azaleas and rhododendrons, require a growing medium that is acidic or lime free. Experts are, however, unanimous on the fact that the perfect mixture for flowering trees, deciduous trees, and conifers are different. In fact, it is important for the grower to continue with the compost combination where the bonsai tree has developed so long. Therefore, when you are purchasing your bonsai, you should always ask the grower about the type of compost mixture it has been growing in. Before using the compost, you should always sieve it with a view to do away with any possibilities of harming the roots of your bonsai.

Why repot bonsai?

Many people often ask why it is necessary to repot a bonsai tree. Although this is a vital aspect of growing bonsai, unfortunately, it is often neglected. Different from any normal plant grown indoors or in a balcony, bonsai trees require containers that completely match with their size as well as style. In Japanese, the term bonsai means a plant or tree grown in a tray. Therefore, neglecting this aspect will often lead to catastrophes. Usually, bonsais that are not repotted at the right time end up spoilt and looking aesthetically horrible.

In fact, bonsai containers are available in a wide array of sizes and shapes. Generally, you can obtain these containers from the growers themselves. Nearly all such trays have their origin either in China or in Japan. If your bonsai tree has a trailing or spreading habitat, you should opt for a flat tray, as it is most suited for such trees. You require a somewhat deeper tray for vertically growing bonsai trees, while further deeper trays for trees that are slender, tall or cascading. Grove or forest arrangements appear most striking when they are displayed in extremely flat trays. They also look excellent when displayed on stone slabs ornamented with some aesthetic rocks. Nearly all bonsai trays are made from stoneware - they may come in two varieties, unglazed or glazed. You will rarely find decorated bonsai trays. The most common colors of bonsai trays include pale green, blue and brown.

Preparing the bonsai container

All bonsai trays come with large holes for draining out excessive water as well as prevent water from stagnating. Often, frequent watering causes the water to stagnate in the trays and this, in turn, results in root rot. Unlike in the case of growing any normal plant in containers, you should never cover the drainage holes using small stones or pieces of broken clay pots. It is advisable that you use a plastic mesh (these will not rust or rot like those made from iron) at the base of the bonsai trays. These plastic meshes should be fixed in their place using a plastic coated wire that is hooked to something outside the tray. Placing a plastic mesh will help to prevent the finely filtered potting compost from leaking out, even if you water the bonsai generously. Use of a plastic mesh also serves other purposes. For instance, it prevents unwanted visitors like the wood louse from entering the bonsai tray.

Removing bonsai from its pot

When the roots of a "pot bound" bonsai tree grow very long and are difficult to manage in the pot or tray they are growing in, it is essential to change the tray or pot. Before you remove the bonsai from its current pot, you need to stop watering it for a while, until the entire compost becomes somewhat dry. However, even when you stop watering your bonsai, you should ensure that the plant does not suffer owing to lack of water. When the compost has become relatively dry, lift the bonsai gently by its trunk. When the compost is somewhat dry, it will help the bonsai to come out of the pot without any difficulty.

Check the soil

It is important to examine the soil from time to time with a view to ensure that your bonsai is healthy. Ensure that the compost is not sheltering any unwanted creatures or substances like wood lice, ants or insect larvae. Checking the soil regularly will also help you to keep an eye on the root development and make a decision as to when you need to repot your bonsai.

Root pruning

Pruning the roots of a bonsai is considered to be a very important aspect of bonsai art, as it directly helps to stunt the trees growth, thereby keeping the tree dwarf. At the same time, root pruning will also facilitate in rejuvenating the bonsai by bringing its feeding roots somewhat closer to its trunk.

Before you prune the roots of your bonsai, you need to remove nearly all the earth from the plant's old root ball by scraping it gently using a special bonsai rake. As you remove the soil from the root ball, you will notice the roots untangling. Always remember that this operation should be undertaken as smoothly as possible, ensuring that you don't cause any damage to the roots, particularly the larger roots, as far as possible. Next, snip the roots using a pair of scissors with wide handles. The roots ought to be cut back to roughly half of their original length. If you notice any roots that are not in their best of health, remove them completely. You should also get rid of all roots damaged while combing the roots of the tree, if any. When you have completed the above mentioned processes successfully, your bonsai is all set for repotting.

According to experts, root pruning is also a testing time for your bonsai tree. This is the main reason why root pruning is always undertaking at the onset of spring, when the growth of the tree is most robust. Having repotted your bonsai, water it generously and subsequently keep it rather dry till the tree establishes itself properly in the new pot.


Selecting the right container is vital while repotting your bonsai. You should ensure that the container should be of the correct size to accommodate the plant freely. Also remember that you should sieve the compost several times, placing the coarsest material just over the drainage layer of pebbles and gravels. This need to be followed by placing successive stratum of compost - the finest compost should be at the top. Subsequently, plant the bonsai and add some amount of the finest soil. If the fine soil is sufficiently dry, it will effortlessly filter down to the roots. Before watering the bonsai, firm the soil lightly.

If the bonsai trees are somewhat large, they may require some kind of support to remain in their place. However, you should never use any type of stake to support such trees. It is advisable that instead of using a stake, you try to keep the root ball of the tree in place using a metal wire - passing it on top of the base and via the drainage holes. You will find that this method is not only effective, but also invisible. However, you should remember to take away the wire after the tree has developed new roots and they have established themselves in the compost. Ideally, you should fill approximately three-fourth of the tray with compost and finish it off by adding a stratum of fine sieved soil on the surface. Use a spatula to firm the soil lightly at the other end of the tree. Alternatively, you may also make use of tweezers. If you wish you can also coat the top layer of soil with a moss layer. The layer of moss will not serve the decorative purpose, but also keep the soil humid after every watering.

When you water your bonsai, ensure that it is done slowly. Continue watering the plant till some excess water flows out from the drainage holes. In fact, watering the bonsai may prove to be a long time job, as the compost that have been used for repotting the plant is supposed to be very dry. Place your bonsai in a place where it is sheltered from the sun and wind for many weeks. This will help to check the moisture from evaporating. You will notice that your bonsai will soon overcome the shock of repotting and flourish once again. You should always bear in mind that the repotting process is actually a traumatic experience for any plant and, hence, you need to act keeping this in view. At the same time, it is necessary to select the appropriate tray before relocating your bonsai. In case, you choose the wrong container and decided to change the pot, it is likely to do irreparable harm to your bonsai. This is mainly because your bonsai will not be able to endure the shock of being repotted in such quick succession.


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