Why Is Your Bonsai Turning Brown? (5 Reasons)

If you see the leaves of your bonsai tree turning brown, you will need to take swift action to solve the problem. 

A bonsai tree with brown leaves is not healthy, and if you don’t take steps to identify and address the issue, it is likely to die.

Overall, quite a few different issues can cause a bonsai tree to turn brown, including poor fertilization, lack of sunlight, and inadequate water. 

It’s also possible for certain diseases, pests, and fungal infections to make the leaves brown.

This article will take an in-depth look into why a bonsai may turn brown and how to reverse the problem. 

5 Reasons a Bonsai Can Turn Brown

1) Poor Fertilization

Very frequently, brown leaves will be the result of poor soil.

A bonsai tree can quickly use up the nutrients in the soil since the container is small.

So, with minimal compost and potting medium, the tree will absorb the essential nutrients it needs rapidly, and if it runs out, it will struggle to maintain rich, healthy foliage.

Specifically, a lack of magnesium, iron, and nitrogen will result in leaf browning.

Thus, to ensure your bonsai gets essential nutrients, you should fertilize it with a diluted fertilizer throughout the growing season, usually in spring, summer, and early fall.

And although you might be reluctant to fertilize your tree if you don’t want it to grow too fast, not fertilizing will lead to leaf browning and poor health.

You should slow down on fertilizing your tree once it reaches maturity, though, but you need to continue to feed it fairly frequently so that it stays happy.

Just don’t over-fertilize your plant because it can suffer if it has too much food. 

You can tell if you have over-fertilized your bonsai tree by looking for a buildup of salt and nutrients in the soil, typically appearing as a white crust.

If this happens, thoroughly rinse the soil and stop fertilizing for a while so that your plant has time to use up the nutrients.

Finally, don’t fertilize your plant during the winter because it will not be growing much at this time and will not need the food.

2) Lack of Sunlight

Most bonsai trees need a great deal of sunlight, although some do not like direct sun.

However, all trees need at least some sun. 

If your bonsai tree isn’t getting enough light, it may turn brown because it will struggle to produce chlorophyll.

If this happens, you will need to move your tree to a place with better light.

A windowsill is often a good option, but bear in mind that some bonsai trees also don’t like getting lots of bright, direct sun.

Therefore, you may need to put up a thin curtain so that your tree doesn’t burn. 

Or, conversely, you can get a grow light and plug it in near your tree to supplement the natural light if you don’t have an adequate window.

3) Inadequate Amount of Water

Brown, crispy leaves can also indicate that your tree is not getting enough water or that it’s getting too much water.

Too much water has similar results to lack of water because it will cause root rot. 

And if your tree experiences root rot, it cannot soak up water and will therefore die of thirst even if you water it regularly.

Similarly, if you simply don’t water your tree, it will quickly die of thirst, and its leaves will turn brown.

So, overall, make sure you give your plant a drink if it looks thirsty, but also allow the soil to dry out a bit in between waterings.

This watering strategy will ensure your plant stays healthy and doesn’t brown. 

4) Disease

Diseases can also cause brown leaves, including brown leaf spot fungus.

And as the name suggests, this will cause brown spots to appear on the leaves.

This issue can affect all different kinds of bonsais, especially outdoor plants, which are more likely to contract the infection.

So, if your bonsai has brown leaf spot fungus or another disease, you will need to treat it using a fungicide. 

You also have to prune the affected foliage and branches.

5) Pests

In some cases, pests can cause leaf browning because they will damage your plant and rob it of the resources it needs to maintain healthy foliage.

Thus, if your plant’s leaves turn brown and you can’t work out why, you should try inspecting it for pests.

Insects that might attack a bonsai tree include spider mites, aphids, mealybugs, scale insects, and thrips, although different trees are vulnerable to pests.

Generally, you can treat most pests that attack a bonsai tree by washing the leaves with warm, soapy water, but this doesn’t work with every kind of pest. 

So, look for instructions on the specific pest your plant has.

Additionally, you can use neem oil to kill many pests, but check that this oil doesn’t harm the plant by first testing it on a leaf.

Conclusion

The leaves of bonsai trees can turn brown for various reasons, and it’s essential to act if this happens to your bonsai because brown leaves indicate your tree needs help. 

Therefore, if browning occurs, check whether your bonsai has enough fertilizer first, and then look into issues with sunlight, water, diseases, and pests.