Watering Bonsai: How To Water Your Little Tree

Your bonsai tree is a long-term project and needs routine maintenance and a good care plan to keep it healthy and thriving. Typically, bonsais are grown in shallow ceramic pots; they are delicate, fragile miniature trees that require daily attention and regular watering.

Part of the attraction of bonsai growing is that the techniques are the unification of science, art, sculpture, horticulture and the best bit, delight. It’s a different way to appreciate and encourage nature.

When you picture a perfect bonsai in your mind’s eye, you’ll see a flawlessly scaled tree or shrub.

As part of your daily care and routine maintenance, you will want to ensure that your tree is healthy and flourishing. Because your miniature tree grows in a small, shallow pot, it will need regular watering.

Understanding how much your bonsai needs is one of the most vital skills you will foster. Without water, your bonsai will not survive, and the fastest way to kill it is quite simply to stop watering it. It’s not as straightforward as you might think.

Sadly, it is commonplace that you might learn the hard way by killing a bonsai or two.

Your bonsai has a restricted root system, so you need to water it frequently. Interestingly, because your bonsai is in a confined pot, it loses its natural ability to self regulate its exposure to water. Commonly, bonsai trees are over or underwatered. Many Bonsai experts consider watering to be an intuitive art rather than a science. Every tree, after all, is different.

Your tree requires repeated watering to enable optimal growth and development.

When To Water: 7 Factors To Consider

The only way to know when your bonsai needs watering is to touch the soil. Over time, understanding the different variants that will make watering protocols easier.

Soil Mixture

Preparing the correct soil mixture is essential for the survival of your tree, so you will need to consider the correct ratios of akadama, pumice, lava rock, organic potting compost and fine gravel.

Akadama is a hard-baked Japanese clay that breaks down and reduces aeration, so it should be used with other well-draining components. Your soil should have a pH balance of between 6.50 and 7.50. Organic potting compost should be a blend of peat moss, perlite and sand; this combination is ideal for water retention. Fine gravel is used at the bottom of the pot to help with drainage.

If you reduce aeration and drainage too much, you risk the chance of root rot.

To increase drainage, add more lava rock, perlite or coarse sand to the mix.


Fertiliser is essential for the healthy growth of your bonsai; it provides your tree with vital nutrients. Fertiliser accelerates the speed of decomposition of the organic components in the soil and the drying out time. To prevent this from happening, use inorganic elements such as pinewood in the soil.

Plant Size

The size of your tree will also affect how often you need to water it. If you have a fast-growing tree, you will need to water it more frequently. You can water outside bonsai trees daily as long as you don’t overwater them. Miniature trees will also need to be watered often.

You might need to use a humidity tray to keep the external parts of the tree slightly moist.

Container Size

The size of the container also plays a massive part in your watering routine. The larger the pot, the more soil it will contain, allowing for better water retention and soil that remains damp for longer. Bonsai trees are grown in small, shallow pots.

You can put fast-growing bonsai trees into larger pots for this very reason.


If your bonsai has exposure to the sun, it will heat the container and the soil, resulting in evaporation, meaning you will have to water the plant more frequently. Ideally, your tree should be in the sunshine in the morning and shade in the afternoon.

Weather Conditions

Humidity levels and wind will affect the soil conditions. It is an excellent idea to protect your tree from any harsh elements, such as strong winds. This is particularly important in the winter months if you live in cold climes where freezing is possible. Bonsai trees thrive in warm and humid climates. If you live in an arid area, consider using a humidity tray.

The tree will benefit from the moisture created by the water and provide an area for drainage.


If your bonsai tree is not maintained correctly, it can be vulnerable to disease. Root rot decreases the efficiency of water absorption. It is important that you routinely check your plant’s health and carefully check leaves for aphids and other destructive pests.

How To Check Soil Mixture: 3 Easy Methods

You mustn’t allow the soil to become too dry, so you need to get into a routine to check the soil each day to determine if it needs watering. There are various easy ways that you can do this. With experience, you may be able to check moisture content by simply lifting the pot and assessing its weight. The heavier the pot, the more water is present.

Soil Moisture Meter

You’ll find that the most accurate way to measure the moisture in the soil is with an electronic soil moisture metre. A moisture metre measures the water content of the soil at the root level. It is a valuable tool that prevents you from over or underwatering your tree. It takes away all of the guesswork. The metre will give you a reading based on a scale of 1 for dry and 10 for wet soil.

The ideal metre reading is 3, keep the probe in place and water your bonsai until it reaches the required level. Ensure that you clean the metre after each use and store it in a safe, dry place.

Finger Method

You can check for soil moisture with your finger by inserting it into the soil to about an inch or so deep. It can sometimes be hard to tell, especially if the soil is cold to the touch. It is not the most accurate of tests but is suitable on occasion.

If you have many trees to test, it’s not the best option.


You’ll need an untreated chopstick, tongue depressor or ice lolly stick. Carefully insert the chopstick into the soil about halfway from the tree’s trunk and the edge of the pot. Don’t be forceful, or you may damage the roots, but push the chopstick about 2 inches deep. Leave it in place for about 10 minutes so that the chopstick can absorb any water in the soil.

When you remove the chopstick, see if it has darkened or has a watermark; this will indicate if the soil is moist. If there is no change in colour, the soil is dry, and it is time to water your bonsai.

If there is slight evidence of moisture, recheck the soil the next day. Rinse the chopstick and leave it to dry.

Don’t forget that these moisture measuring techniques calculate the moisture retained in the soil at the root level. The general rule of watering your bonsai is applied here, but if you have a succulent bonsai such as jade, euphorbia or crassula, consider that they thrive during their dry periods.

Make sure that you pay attention to your tree type.

5 Key Watering Tips To Remember

DO NOT Overwater Your Bonsai

Overwatering is one of the biggest threats to your bonsai. Many beginners are so concerned about underwatering the trees; they accidentally do the opposite. Overwatering your tree can kill it. It can take many years to master the art of accurately watering your bonsai tree.

It also takes a while to see if the tree is overwatered; it’s a gradual process.

Checking the moisture of the soil every day is an excellent step to combating overwatering problems. The soil should never be constantly wet. The roots need oxygen to breathe to make food by photosynthesis and to breathe. Plants need to breathe just like people and animals; they need oxygen to convert food into energy.

The relationship between air and indoor plants is essential to keeping your plants looking their best and in peak health.

There are various telltale signs that you are overwatering your bonsai; it’s essential to keep a watchful eye.

o Yellowing leaves that will ultimately fall off

o The stems begin to die

o Branches are small and weak

o The trunk looks unstable

If you think that you are overwatering your bonsai tree, it’s important to check by removing the tree from the pot to check that the roots are healthy. Healthy roots should be white and firm; overwatered roots will be mushy, fetid smelling and brown.

If you have overwatered the plant, remove as much of the rotten roots as possible to try and prevent the tree from dying. Remove any dead or yellowing leaves and consider removing a small canopy section to avoid additional stress until the bonsai recovers fully.

Rinse the tree and roots and repot, preferably into a new container or the disinfected old pot so that you avoid infection.

Allow your tree to recover in a well-lit area, but not in direct sunshine. Chamomile is a natural antifungal solution that you can add to your watering routine. Ensure that you check the soil so that you don’t damage the tree any further.

What Kind Of Water Should I Give My Bonsai Tree?

Generally, if tap water is good enough for you, it will be good enough for your bonsai.

Before you use the water on your bonsai, it’s good to check to see if your water is within healthy limits. If you have hard water, it can create a build-up of lime or salt in the roots of your tree, which could cause a lack of vigour and deterioration in health. If it is possible to collect rainwater in a pottery urn, this will reduce the risk of lime and salt build-up.

If you have hard water, you might notice a mineral build-up around your faucet fittings, soapy residue in your sink, spots on your dishes and even dry, itchy skin.

If your water contains substantial amounts of chlorine, let the water sit in your watering can overnight so that the chlorine evaporates. It is essential that your bonsai has clean, fresh water.

Watch For Signs Of Underwatering

Underwatering is another common way to kill your bonsai tree. Unfortunately, because the trees are in pots, they lose the ability to regulate their moisture intake. As your plant is in such a small pot, it can dry out very quickly. Without water, your tree’s entire ecosystem will collapse as it dries out.

For your bonsai to survive, you should water it regularly to release sufficient nutrients to promote healthy growth. Always test the soil and ensure that you follow the correct watering procedure.

There are a few signs to watch for that are indicative of underwatering.

o Yellowing leaves

o Dry or brown leaves

o Dry soil

If you have underwatered your tree, use the immersion method to hydrate the roots. Firstly, you’ll need to find a waterproof container that is big enough to hold your pot and tree. Submerge the tree so that the water completely covers the pot and comes about an inch up the trunk. As you submerge the tree, you’ll see bubbles rising to the surface; this indicates that your tree is underwatered.

When the bubbling stops, it means that the soil has reached the roots and they are hydrated. Remove the tree and allow it to drain. Replace any soil or pebbles that you may have lost during the process.

Bonsai specialists don’t recommend that you carry out this procedure too often; it can come with its own set of problems and damage the roots. If your tree is regularly drying out too quickly, it’s worth considering repotting it and changing the soil to a mixture that is less fast draining.

Be Careful Of Root Rot

Root rot is caused by frequent overwatering and constantly wet soil, and lack of air. When the soil remains wet, the roots rot, bacteria spreads throughout the root system, and microorganisms take over the dead tissues. The roots will become smaller, and the entire tree becomes unstable, which leads to its death. Root rot is generally found when the tree is repotted. The roots will be black and dusty.

If you do come across this, ensure you cut out all of the dead roots to prevent root rot from spreading.

Don’t Set A Watering Routine

Bonsai trees need more watering than standard houseplants because of the shallow pots and course, well-draining soil mix. There are many factors and protocols to consider when watering your bonsai. You mustn’t have a strict watering schedule. You need to understand the nature of your tree to prevent under or overwatering.

You should only water your tree when the soil is slightly dry to the touch, or you have done a soil test.

As you gain experience, you’ll quickly notice when your tree requires water. Just to make things more complicated, the watering requirements will change throughout the year depending on humidity, heat and if your tree is in its growing or dormancy phase. You may need to water your plant twice a day if you live in a sweltering and arid climate. Consider regular misting to maintain a level of humidity which may be difficult, especially if your plant is indoors.

Central heating during the winter and air conditioning in the summer can cause a dry environment.

Regularly misting your tree creates humidity and keeps it free of cloying dust.

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