The Care And Maintenance Of Bonsai Trees

Maintaining a bonsai is not nearly as difficult as is commonly thought. However, since bonsai are planted in small bowls, some important basics must be observed when watering, fertilizing and repotting.

How easy is it to keep a Bonsai Tree?

Although keeping a bonsai tree is actually much more complex than keeping an ordinary houseplant, you will certainly be able to keep a bonsai if you stick to certain basic rules. The most important aspects to consider are irrigation, fertilization and choosing the right location.

Taking care of the bonsai is an important part of our online bonsai course, which is specially designed for beginners. You can find more information and a free lesson at the Bonsai beginners course.

Bonsai watering / watering bonsai

How often does a bonsai tree need water?

The most important element in keeping bonsai trees is proper watering. How often you have to water depends on several factors, such as Tree type, size of the tree, soil mixture and the volume of the shell, season, climate, location, etc. It is therefore important to observe the tree closely so that you can recognize the right time. The guidelines below will help you do this.

As mentioned earlier, the frequency with which you need to water your tree depends on several factors. It is not possible to give an exact indication, but rather it is a matter of precise observation in order to determine the right moment for pouring. The rules below will help you:

  • Water the tree as soon as the soil has dried
    This means that you should rather not give water when the soil is still damp, but when it feels slightly dry. You can check this with your fingers, about an inch deep. In time, you will learn to see when your tree needs watering without feeling a finger.
  • Never water routinely
    Look at your trees individually rather than watering them with a daily routine and always at the same time.
  • Use the correct soil mix
    The soil mix also has a very large influence on the frequency of irrigation. A soil mixture suitable for most bonsai trees consists of Akadama, fine gravel and humus (e.g. potting soil), in a ratio of ½ to ¼ to ¼. However, if you do not have the opportunity to water frequently, it is better to use a mixture that can retain moisture for longer or contains more humus (e.g. potting soil). You can find more information on soil mixes under the article of the same name on our website.

When to water

The morning and evening hours are best for watering. In the midday or early afternoon hours, however, you should avoid watering with very cold water, because the soil is warmed up by the solar radiation and would cool down quickly through watering, which in turn is unfavorable for the tree roots. Nevertheless, it must always be clear that your tree must be watered when it gets dry, no matter what time of day.

How to water

As already explained, a bonsai tree should be watered when the soil is dry. At this point the tree needs plenty of water and the soil needs to be soaked in plenty until all the roots are completely wetted. To do this, pour water copiously on the soil until it flows freely from the holes in the bottom of the bowl. Repeat after a few minutes to make sure all areas are well soaked.

Watering the bonsai is one of the topics in our online bonsai course, which is specially designed for beginners. You can find more information and a free lesson at the Bonsai beginners course.

Use a watering can with a fine effervescence to prevent the soil from being washed out of the pot. Rainwater is particularly suitable for watering bonsai trees because it contains little lime. If rainwater is not available, conventional (stale) tap water is also suitable.

The fertilization of bonsai

When should you fertilize bonsai?

It is vital for your bonsai to be fertilized regularly during the growing season. Normal trees can expand their root system in search of nutrients. Bonsai, on the other hand, are planted in relatively small bowls and need fertilization to maintain the nutrient content of the substrate.

The main components of the fertilizer

The three basic elements of any fertilizer are nitrogen (N), phosphate (P) and potassium (K), each of which serves different purposes. Nitrogen promotes the growth of leaves and stems, phosphate promotes vigorous root growth and potassium ensures the formation of flowers and fruits. Different ratios of NPK are used for different trees at different times of the year, which is an important consideration when fertilizing bonsai.

When should you fertilize bonsai?

Fertilize throughout the tree’s growing season, from early spring through into fall. Indoor bonsai can be fertilized all year round. While this is sometimes controversial, do not fertilize newly potted trees for a month. Sick trees are also not fertilized.

Which fertilizer should you use?

It is very important to use the right fertilizer. In early spring, a fertilizer with a relatively high nitrogen content is recommended (such as NPK 12: 6: 6) to promote strong growth. During the summer, a more balanced fertilizer (such as NPK 10:10:10) is appropriate, while in autumn a fertilizer to develop winter hardiness should be selected (e.g. NPK 3:10:10).

A few exceptions should not be left unmentioned: to stimulate a bonsai to bloom, you should use a fertilizer with a high potassium content (such as NPK 6: 6: 12) and for older trees you should use a fertilizer with a slightly lower nitrogen content (N) or fertilize with a lower dose.

Even if “bonsai fertilizer” is a fertilizer like any other, it is often easy to find the right NPK values ​​when buying from an (online) bonsai shop. Any fertilizer with the correct NPK ratio is ideal. You can choose whether you want to use liquid or solid fertilizer, this does not play a major role, but you should carefully follow the instructions for use on the package.

How do you fertilize the trees?

Fertilize your bonsai in the amounts and at the intervals recommended on the fertilizer package. The recommended amount can be reduced slightly if the bonsai is mature to balance their growth instead of stimulating it. When using solid fertilizer, fertilizer baskets are helpful as they ensure that the fertilizer stays in place. Never over-fertilize your trees, otherwise this has serious consequences for their health.

We can highly recommend the following bonsai fertilizer with which we have had very good experiences:

Repot the bonsai

Why do we need to repot a Bonsai Tree?

Regular re-potting is essential to prevent the root ball from compacting and the bonsai from starving to death. Repotting doesn’t keep the tree small, it provides the tree with fresh substrate that it needs to grow and thrive.

How often do you have to repot a Bonsai Tree?

How often a bonsai needs to be repotted depends on the size of the bowl/pot and the type of tree. Fast-growing trees need to be repotted every two years (some even every year), while older, mature trees need to be repotted every 3 to 5 years. Do not repot routinely, but rather inspect your trees in early spring each year by carefully removing them from their shells. A bonsai needs to be repotted when the roots grow in a circle around the bale. If the roots are still in the ground, wait another year before checking again.


Repotting usually needs to be done in early spring when the tree is still in hibernation. In this way, the stressful effect of repotting is limited to a minimum, because the tree does not yet have fully grown leaves to take care of.

Repotting in early spring also has the advantage that the interference with the root system can be quickly compensated for when the tree begins to grow.

Bonsai substrate mix

The right mix of substrates is critical to the health of your trees, it should dry quickly enough to keep the roots from rot, but it should also absorb enough water to supply the tree. Although some tree species require special substrate mixtures, the following mixture is suitable for most trees:

Mix Akadama, pumice and lava granules in a ratio of 50% to 25% to 25%. If you don’t have the ability to water your trees often, choose a more water-retaining mixture (use more Akadama or add humus), while you should use a faster-drying mixture (use more lava granules) if you are in a wet climate Life. Read the article on bonsai substrate for more information.

Worth knowing!
The most important thing to consider is the time of year. Repot your tree just before budding begins, in early spring.

Bonsai substrate / bonsai soil

Recommended mixes

Using the right mix of substrates for your bonsai is vital. The substrate is important to provide the trees with nutrients, but it also needs to dry well, be adequately ventilated and hold water.

Although most (online) bonsai stores offer ready-mixed substrates, you can do this yourself, which saves money, and you can tailor the mixes for each tree species individually.

Bonsai substrates

There are a number of properties that a good substrate mix must meet

  • Good water storage
    The substrate must be able to absorb and hold sufficient amounts of water to provide the bonsai with sufficient moisture between waterings.
  • Good drainage
    Excess water must be able to drain off immediately. Substrates with poor drainage properties stay too wet, are poorly ventilated and collect salts. Too wet substrate (soil) leads to root rot and causes the tree to die.
  • Good ventilation
    The particles of a bonsai substrate mixture should be large enough to leave small gaps between the grains where there is air. Aside from the fact that the roots need oxygen, this is also important for beneficial bacteria and mycorrhiza so that the nutrients are processed before they can be absorbed by the root hair and transported to the photosynthetic leaves.

A coarse-grained, structurally stable, inorganic substrate enables water to run off quickly and fresh air to flow into the substrate. A compacted, organic soil that does not have a granular structure is poorly ventilated and dries too slowly, which leads to disease of the roots and the whole tree, as well as root rot.

Bonsai substrate components

The most important components of the substrate mixtures for bonsai are Akadama, pumice gravel, lava granulate (granulate), organic humus soil and fine gravel (chippings)

From left to right: organic humus soil, akadama, pumice gravel and lava granules.

Akadama is a hard-dried clay granulate that is specially obtained for bonsai purposes and is available at almost all (online) bonsai shops (including our bonsai shop). It should be sifted before it is used. Note that after about 2 years, the Akadama granules will begin to disintegrate, which significantly deteriorates ventilation. This means that regular repotting is necessary. Akadama is relatively expensive and is therefore sometimes replaced by similar burnt clay granules that can be purchased in garden centers or in building materials stores. Even cat litter is sometimes used, ask your bonsai forum which brands are recommended.

Pumice gravel is a soft, volcanic product that can absorb water and nutrients quite well. When used in a substrate mix, it helps retain water and helps the roots branch well.

Lava granules hold water and give the substrate mixture a good structure. Roots cannot grow into the lava granules.

Potting soil contains peat, and sometimes perlite and sand. It has a few drawbacks (it absorbs a lot of water, does not ventilate, and it does not dry well), but it works very well as part of a mix.

Fine gravel is of great importance to achieve a well-drying and aerated bonsai substrate. It is also used as a drainage layer at the very bottom of the bowl.

Different tree species require different substrate mixtures, which is why you should check our tree species guide to find out which is the optimal mixture for each tree. However, we can specify two common mixtures, one for deciduous trees and one for conifers. Both mixtures consist of Akadama (the water-storing component), pumice gravel (good structure) and lava granules (for ventilation and drainage).

Keep in mind that both mixes can and should be customized to suit your local conditions. If you don’t have the time to check your trees twice a day, increase the Akadama (or even humus) levels in your substrate mix to increase water retention. If you live in humid climates, add more lava granules (or gravel) to your mix to improve drainage properties.

Bonsai substrate mix for deciduous treesBonsai substrate mix for conifers
50% Akadama33% Akadama
25% pumice gravel33% pumice gravel
25% lava granules33% lava granules
Recommended bonsai substrate mixes

Worth knowing!
When it comes to substrate, every expert seems to recommend a different mixture. Try and experiment what works best for you!

The site

Inside Outside?

It can be difficult to determine the best location for your bonsai because of several factors (local climate, season, tree species, etc.) to consider. The best thing is to know exactly what type of tree you have and then look for specific information.

A rule of thumb

Most outdoor bonsai are best placed in a bright location, about half the day in direct sunlight and protected from the wind.

Indoor bonsai are also best in light, but some species prefer as much sun as possible, while others do better in partial shade. Indoors like a location with a largely constant temperature.

Choosing the right bonsai pot

The importance of choosing the right bowl for bonsai is often underestimated. The bowl (as well as additional means of presentation such as grass, moss, stones, figures and a presentation table) are important components of the composition and should be carefully selected in order to bring out the tree to its best advantage.

General guidelines

Bonsai are planted in small bowls, often imported from Japan or China. Japanese pottery is known for its high quality and is often quite expensive, elegant, subtly glazed or unglazed, while Chinese products are usually cheaper (but the quality is getting better and better) and often brightly glazed. An exception, however, are ancient Chinese bonsai pots, which are priceless and very rare.

Old bonsai, which no longer require major design interventions and have already been re-potted many times and pruned at the roots, are adapted to live in small bowls. Younger trees, however, need more space to grow and are gradually being prepared to live in smaller and smaller trays by cutting their roots each time they are repotted. Young trees can be planted in less expensive or plastic trays available from (online) bonsai shops.

The size of the bonsai pot

Trees that are still in development should be planted in relatively large containers that give the roots enough space to grow and help the tree survive the major design interventions, such as the first basic cut. Older trees already have a more compact root system and can be planted in smaller bonsai pots, in which case aesthetic considerations become more important.

Bonsai pots, aesthetics

Choosing a bowl that really fits the tree is difficult because various aspects (such as the shape, the choice between glazed and unglazed, etc.) have to be taken into account. Some basic rules of thumb can help to find the right bowl (these should not be viewed as strict rules, aesthetic considerations are to a large extent a matter of personal taste!):

  • Use unglazed bowls for conifers (e.g. pine).
  • Glazed, but in some cases unglazed, bowls can be used for deciduous trees, but brightly colored bowls should be reserved for flowering and fruiting bonsai.
  • The length of the bowl should be around two thirds of the tree height.
  • The depth of the shell should be roughly the same as the thickness of the trunk at its base (except for particularly thin, young trunks).
  • For trees that appear masculine, angular bowls should be chosen, for more gently shaped, feminine-looking trees, rounded shapes.

Ultimately, the most important thing is that the shell you choose is large enough to maintain the health of the tree in it, and that the shell is visually subordinate to the tree (simplicity is often key). For inspiration, take a look at the trees and their bowls in the Bonsai Gallery.

A bigger bowl for health. A rule of thumb is that a bowl should not be longer than 2/3 the height of a tree. Here, however, the bowl deviates from this rule because the crown is so large, almost as wide as it is high. The bowl is not only so large for aesthetic reasons and for the optical balance, but because the spreading branches are also supplied by a correspondingly extensive root system that requires sufficient space. That’s why the crown of the tree is so big, almost as wide as it is high. The choice fell on a yellow bowl, which absorbs and enhances the red-yellow autumn colors of the leaves.

Bonsai pests and diseases

Like any other living plant, Bonsai can be attacked by various pests or diseases. However, if your plants are healthy and well cared for, the risk of infestation is reduced to a minimum.

In a nutshell: Make sure that your trees are in the right substrate mix, that you know how and how often they have to be watered, that you are not fertilizing too much or too little and that your bonsai is in the right location. Even if the likelihood that healthy Bonsai trees will be infested is small, it cannot be excluded. As it is often difficult to pinpoint the problem correctly, it is advisable to take a picture and ask for help in the bonsai forum.

How to recognize pests and diseases in bonsai trees

These are some of the most common problems you will encounter with your bonsai:

Leaf loss
The leaves suddenly become withered, dry, or yellow and fall off. This is often the result of a sudden lack of water. However, when the leaves slowly turn yellow and die, it is usually the result of overwatering, overfertilization, or lack of nutrients.

Common pests on bonsai
Try to identify them by either taking photos of the pests and asking for advice in an internet bonsai forum.

Once you have identified the pests, buy a suitable spray (chemical or organic) that you can use to treat the infected trees. Carefully follow the instructions for use and possibly start with a lower dosage. You can increase the dose later if necessary.

Virus and fungal diseases

Viral diseases can manifest themselves as pale leaf color and sudden death of branches. Place such trees separately from the others to avoid contamination. Remove the infected parts. In the event of a fungal attack, you also inject a fungicide.

Bonsai overwintering

During autumn, the outdoor trees prepare for winter by letting the new shoots harden and the deciduous trees shed their leaves.

During the winter, the trees enter a dormant phase that is important for the bonsai, so you shouldn’t want to over-protect them by bringing them indoors. (Sub) tropical trees are an exception and should be indoors in winter.

Bonsai overwintering

In nature, the trees are often exposed to temperatures of -10 ° C and below. However, the roots of the trees are too deep in the ground to freeze through. As long as the roots of the bonsai are protected, low temperatures are not a serious problem because the leaves of the evergreen trees activate their own protective mechanisms when it comes to hibernation.

Placing the trees in a greenhouse or cold house over the winter is recommended in cold regions because the roots in the shallow bonsai pots freeze through quickly. If such possibilities are not available, the insulating material can be wrapped around the bonsai pots.

If you live in (sub) tropical areas, you can usually leave the trees outside unprotected.

If the bonsai are in hibernation, take care that the trees are not exposed to high temperatures for long periods of time (e.g. open the greenhouses when they are heating up on sunny days), as this can wake them up from the rest phase. When it gets cold again, the trees have lost their natural frost protection and the buds can die off.

During the winter you should keep a close eye on your Bonsai Tree. Water when the substrate dries. The trees don’t need a lot of water when they are resting, however, so be careful not to water too often. Also, check regularly for pests or diseases. You can put the trees back out in spring, but be prepared to protect the new shoot from any late frost.

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