Indoor Bonsai Tree Care

Indoor Bonsai Tree Care and where you put your bonsai tree is a major factor in how healthy it will be. In reality, there is no such thing as an indoor tree, only trees which can survive inside. Houses are generally darker, warmer and drier than outdoors. Consider light, temperature and humidity when placing your bonsai.

Bonsai need plenty of light

Areas near windows are good. Windows which catch full sun all day are great in autumn, winter and spring but may be too hot and sunny in summer.


Avoid sources of heat such as radiators and televisions. A cooler room is better than a warm room. You cannot keep a bonsai on a window ledge if there is a radiator below it. If you use the radiator even once the heat will dry out and kill the tree.


The best rooms to keep indoor bonsai in, tend to be kitchens and bathrooms due to the moisture from the taps and sinks.

Keeping the tree on a drip tray will allow some water to sit under the pot. This will evaporate slowly and increase the humidity level around the tree.

Mist spraying can also be done using a small mister available from most garden centres. The aim is to keep the humidity as high as possible in order to stop the tree from drying out.

If in doubt

We find kitchens are good places. Somewhere near a window. A south-facing window is best. A north-facing window is going to be too dark. Conservatories and porches are even better, especially if some shade can be given from the strong summer sun.

We recommend that all trees are put outside for at least the summer to benefit from the increased light and fresh air. This will reinvigorate the tree.

Shelves, bookshelves, mantlepieces, coffee tables and desks

Beginners to bonsai will tend to underestimate how much light a tree needs to grow. It’s remarkable how much darker it gets with every foot you move away from a window. People very frequently choose a location that they would like the tree in live in without really thinking about if the tree will get enough light. Shelves, bookshelves, mantlepieces, coffee tables and desks are generally not ideal. Bonsai trees seen on TV and in films are not a guide to suitable locations, they have just been put there for the filming.

How to water a bonsai tree

Bonsai are usually kept in small bonsai pots, due to this, they require regular watering. They are kept in small pots mainly for an aesthetic look.

In warm weather, they will need to be watered much more than in cold conditions.

Water when the top of the soil starts to feel dry to the touch. After a time, you will be able to tell when the bonsai needs watering by lifting it and feeling its weight. The look of the soil, and its colour, is also a useful guide.

Pot immersion

Very effective – fill a clean bowl with cold water and sit the whole tree in for a few moments. Some soil and granular feed can be lost however which will need to be replaced periodically. Be careful when a tree has recently been repotted as much soil can be washed away, it is better not to immerse the pot of recently repotted trees. Ask the seller of the tree when it was last repotted.

Water from above

Pour water onto the soil surface. Be gentle or soil can be washed away.

Keep the tray filled up with water to provide humidity.

Which is best?

We find that trees which have been recently repotted should be watered from above as the loose soil can we washed away. Trees which have not been repotted for a while can be immersed in a bowl of water or watered from above. If the soil will not easily accept water (as it tends to run off the soil surface) it should be immersed.

Either way, when you water – soak. Give the tree plenty of watering.

What is over-watering?

Over-watering occurs when the soil is constantly waterlogged over a period of time. The waterlogged roots rot, damaging the tree. It occurs when excess watering cannot drain away.

People sometimes worry about this. While it is possible to over-water, underwatering kills trees far more quickly.

Bonsai trees growing in small bonsai pots, or larger trees in higher quality bonsai soil, are unlikely to suffer from over-watering indoors unless you are drowning the tree.

Bad bonsai pots

Bonsai pots can be cheap or very expensive. Bad bonsai pots do not have drainage holes, so the excess water cannot drain away. Watch out for those ceramic pots which have a plastic plant pot inside. These hold stagnant water and should be avoided.

How to feed a bonsai tree

As with all plants, feeding promotes growth and health.

Liquid or granular bonsai fertiliser can be used. Smaller bonsai benefit from liquid feeds whereas larger bonsai suit granular feeds. This is only because the granules can fall or be washed off smaller bonsai more easily. Also note that if you water by immersing the pot in water, granular feed can be lost into the bowl. Where liquid feed is used, go for liquid bonsai food. If you use a higher-strength liquid feed, dilute it down to less than the manufacturer’s recommendation.

Our granular feed

Work a small amount (a tablespoonful) of the granules/powder into the soil. Try to press them in as watering can wash them off. They will gradually melt into the soil, feeding the tree. They can go mouldy but don’t worry, it won’t harm the bonsai. When it disappears, use more.

Liquid feed

Liquid feeds need to be mixed with water. Follow the instructions on the pack. Never use too much food. If in doubt, make the food up at half-strength. Feed every two weeks.

Use low-strength feeds – NPK 7-7-7 or less.

How to prune your bonsai

Pruning your bonsai is essential to maintain its shape and keep it healthy.

Long shoots weaken the fine branches, transferring the energy to the tips.

With scissors, trim new shoots back to one or two sets of leaves.

Your bonsai has individual branches. It is not a bush. Prune growth to maintain the gaps between the branches.

Make pruning a regular task, rather than leaving your bonsai to overgrow. Start soon after you get the tree, don’t leave it too long to start pruning.

Many styles of bonsai feature a broad triangle shape. Any new growth which breaks this outline can be removed to prevent the tree from looking overgrown. You can also see that there are empty spaces between the branches. These empty spaces will fill up with new growth which should be pruned off.

How to repot

All potted plants need to be re-potted from time to time.

Here is our guide to repotting bonsai trees

There is nothing complicated or difficult to worry about. Your bonsai can grow surprisingly quickly. It will need re-potting after a couple of years in order to keep it healthy.

Ease the tree out of the pot. Inspect the roots. If there are lots of roots and little soil, it is time to re-pot. Tease out the long roots with a root hook so that they hang down from the root ball. Trim these off with scissors. Put fresh bonsai soil in the bottom of the pot. Put the tree back in. Push the soil around the root ball. Fill any space with fresh soil and work it in gently with your fingers.

Water gently from above with a watering can. Do need feed for a month or so.

Problems with indoor bonsai trees

Having worked with indoor bonsai trees for many years, further thoughts spring to mind.

Sub-optimal location

We’ve said a number of times on various pages, that growing bonsai trees indoors is not the same as growing them outdoors. Beginners in bonsai often assume that bonsai trees are the same as houseplants. Sadly, this is not the case.

The key problem is that our indoor environments are not suited to trees. It tends to be too hot, too dry and too dark. Generally speaking, trees like bright, cool, humid air. If you think about it – bright locations indoors often get very hot. Whereas dark locations are cool. Finding the right balance is hard. Finding good spots requires experience and often simple luck.

Then there is humidity. You know the feeling you get when you walk outdoors early on a summer morning – the dew on the grass? Trees outside have been in this humidity all night, helping them to cope with the drier heat of the day. Trying to replicate this indoors is hard. In an air-conditioned office, even more so. Keeping the soil well watered is good but is not a substitute for the lack of humidity in the air. When bonsai care guides talk about misting the tree, it is this that they are trying to combat.

Forcing Growth

“It was growing really well for a few months and then it just seemed to go downhill.”

This is something we here quite often. The explanation is that it has been the warm indoor environment that has been forcing the tree to grow, rather than the light. If you heat many plants up and give them plenty of water, they will chuck out new growth.

The problem is that the tree doesn’t get enough energy back for the amount it has put in. After a while, this exhausts the tree.

Long, Leggy Growth and Big Leaves

“When it arrived, my bonsai had nice little leaves. Now, the leaves are big and the growth looks long and straggly.”

Again, the problem is light and heat. Think about trees which grow in woods. The trees in the middle of the wood are tall and thin. They grow like this as they are searching for the sun. Now think about a tree growing alone in a field. It grows in a completely different way, as it gets all the sun it needs. Mix this with the forcing thing that we just mentioned.

Mouldy Soil

“The soil on my bonsai tree has white mould growing on it.”

Indoor bonsai trees are often grown in compost-rich soil. This soil contains a high proportion of organic materials. It could be peat, coconut fibre or other plant matter. This helps hold water, meaning that you don’t have to water to frequently as you need to with a grittier, more free-draining mixture.

The problem is that this soil is perfect for mould to grow. Warm, damp, organic soil mixed with warm indoor air and poor air circulation. It doesn’t hurt the tree but it does look unsightly.

It can be a sign that you are over-watering but this is not for certain. Please don’t read this and then stop watering, or your tree will die. Hang back just a little, maybe another day and see if this helps.

Try to increase airflow around the tree. Hopefully, it is in a location that gets good airflow but if not, consider moving the tree. You can also spray with a fungicide spray, available from garden centres and online.

When you make changes

Always remember that trees work in a different timeframe to people. Any changes that you make will take at least a month to take effect. So, if you change anything about the tree care, do not expect to see different results immediately.

If you keep constantly changing things – location, watering, feeding or pruning regimes, you’ll never get a chance to figure out what works for you.


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