Watering bonsai: how much& how often to water the small tree?

Bonsais need special attention in terms of water [Photo: Karin Lirapirom/ Shutterstockc.om]

Due to the shell culture, there is little room for error in the care of a bonsai. Especially the watering can quickly become a source of error here. Because the limited shell volume and the rather permeable bonsai soil make frequent watering necessary – and also too frequent watering a problem. The bottom line is that how often you need to water depends on several factors, which we’ll outline for you below.

Like any plant, bonsai needs water to survive. Due to the isolated culture form of the bonsai in a bowl, meticulous attention must be paid to watering as needed. This is even more difficult with bonsais than with most other potted plants, because the bowls usually offer very little substrate as a water reservoir. In addition, bonsai soils consist of a large proportion of inorganic materials and can store water poorly anyway. So bonsais need to be watered in relatively short intervals. But not only the watering distance and watering method is crucial – the choice of a suitable culture tray and a suitable bonsai soil is also essential. We clarify all questions about watering bonsais.

TipUnfortunately, enlarging the bonsai bowl is not an option that could solve the watering problem. Because increasing the root space would lead to – bonsai-untypical – strong growth. Substrates that store water too well are also not a good idea: they lead to low root aeration and thus quickly to oxygen deficiency at the root and root diseases.

When should you water your bonsai?

For bonsais, the watering schedule should be adjusted to the individual plant. If you water without taking the bonsai into consideration, you risk waterlogging or the complete drying out of the substrate especially quickly in the case of tray culture. Both should never happen. Therefore, you should water your bonsai as soon as the substrate has dried superficially. For conifers and succulents, the substrate can also be a little drier at times. You can easily recognize drying by the lightening of the substrate or by simply touching it. It is best to check your bonsai substrate daily. Because especially in the summer it can happen that several times a day you have to reach for the watering can. On hot days, water only in the morning or evening hours. Even in winter you should always keep the substrate moist. Here, however, watering intervals are much longer due to the reduced water consumption of the bonsai. Bonsais that overwinter in the garden are watered only on frost-free days. Thus, when to water a bonsai depends on the drought tolerance of the species, the substrate and the climate.

Due to the small substrate volume, a bonsai needs water particularly frequently [Photo: 3000ad/ Shutterstockc.om]

Summary: Watering Bonsai When?

Water as soon as substrate has dried on the surface (check daily!)
Conifers and succulents are more drought resistant than deciduous bonsais
Keep substrate moist even in winter

Tip: High quality bonsai soils are airy and still store and distribute the watering effectively. For this, for example, swellable clay minerals are responsible, which at the same time also absorb nutrients and release them as needed.

How often and how much do you need to water bonsais?

So there is no fixed period for the watering interval. More importantly, how long it takes to water your bonsai again depends on a number of factors:

Water requirements of the respective plant species: In general, conifers are watered rather little. The rule here is, depending on the substrate, let it dry out as much as possible.
Growth rate and age of the plant: The faster your bonsai grows, the higher the water consumption will be. Older bonsai grow much slower than younger plants and therefore need less water.
Season and temperature: In summer, the water requirement is higher than in winter due to evaporation from sunshine and shoot growth. Here the plants rest and are therefore watered reduced. The warmer the bonsai is in the winter, the more water it will need in the dark season. Room bonsais, which stand in the heated dwelling, need therefore also in the winter water regularly.
Water retention properties of bonsai soilThe higher the percentage of organic substrate, the higher the water storage capacity. This will also lengthen the watering intervals.
Size of the plant: A large bonsai has more biomass compared to a small bonsai, which evaporates water. As a result, the basic need for water is also higher.
Location: The sunnier your bonsai is, the more watering water is lost to the tree through evaporation. Evaporation is highest at a sunny window location.
Surface of the planting tray: The surface of the planting tray also has an influence on evaporation. The larger this is, the more water evaporates and it must be watered more often.

It is best to pay attention not only to the environment and substrate of your bonsai. Also find out about the specific needs of your bonsai species in terms of water requirements so that you can better plan your watering sessions.

How to water a bonsai properly?

To water your bonsai properly, you need to completely saturate the substrate. Proceed as follows when watering your bonsai:

Always use rainwater or soft tap water at room temperature
Water with watering can until the water flows out of the bottom of the bowl
Repeat the process after a few minutes

Hard tap water should be avoided to prevent deposits on the roots and on the vessel, as well as an increase in pH. Alternatively, you can use the immersion method for smaller bonsais. When doing this, immerse the tray in a container of water for a few minutes until no more bubbles rise to the surface of the water. During this time the substrate can soak up well. Then drain off the excess water.

Tip: For bonsai soils with a high clay content, you should always resort to the immersion method.

In order to water your bonsai properly, your bonsai bowl definitely needs a drainage hole. Otherwise the water cannot drain off and waterlogging forms. If waterlogging occurs, your bonsai will react with brown leaves, which will be shed sooner or later, and dead branches. More reasons for leaf drop in bonsais can be found here. For bonsai species that come from tropical areas and are accustomed to a humid climate, you should regularly reach for the water sprayer. How to increase the humidity. In winter, this is especially important for indoor bonsai to compensate for the dry heating air.

Bonsais that are accustomed to a humid climate will appreciate an occasional sprinkling to increase humidity [Photo: jayjued/ Shutterstockc.om]

Summary: Bonsai how often and how much watering?

How often to water depends on many factors: Keep an eye on your bonsai for this reason
Water soaking with soft tap water or rainwater
Use immersion method for substrates containing clay
Spray bonsais that need high humidity regularly
Always use a tray with a drainage hole to avoid waterlogging

Bonsais, however, need not only water but also nutrients to grow properly. You can read all about the correct fertilizing of bonsais here.

Many thanks to Floragard for the support!

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Virginia

I studied plant biotechnology, and in my studies I was often confronted with the serious consequences that ignorance and misinformation can have on the natural world. That is why I am particularly interested in bringing man and nature closer together again.
Favorite fruit: raspberries, strawberries and pineapples
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