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Why Is Your Bonsai Dying? (4 Common Reasons)

While the process of keeping a bonsai alive can be intimidating for beginning bonsai enthusiasts, know that signs of ill-health don’t necessarily mean your tree will die. 

Most bonsai trees are very hardy and can survive occasional slip-ups in maintenance.

But, the real question is, how do you know why your bonsai is dying?

Your bonsai tree is unlikely to die from old age, so a more common and usually fixable issue is probably to blame. 

The most common of these issues include underwatering, overwatering, root rot, improper nutrition, pests, a lack of sunlight, or temperature control problems.

In this article, we’ll examine the root causes of dying bonsai trees, how to isolate the problem affecting your tree, and how to remedy the situation before your bonsai’s health issues are irreversible.

4 Common Reasons a Bonsai Can Start Dying

If your bonsai is showing signs of ill health, you may be concerned and wonder to yourself, “why is my bonsai dying?”

One or more of the below problems are likely to blame. 

Reason One: You Put an Indoor Bonsai Outside, or an Outdoor Bonsai Inside

There are very few species of trees that can thrive both indoors and outdoors, so your bonsai tree is likely meant to live in one or the other.

Some bonsais are tropical or subtropical species of trees, so they simply can’t survive in a four-season outdoor environment filled with wind, rain, high heat, and snow. 

They must live indoors in a climate-controlled environment to survive.

Other bonsais are evergreen trees or trees that require four seasons. 

These trees won’t survive in a climate-controlled environment where they cannot go dormant or shed their leaves.

So, make sure you understand where you need to keep your bonsai.

Reason Two: Not Enough Light

Indoor bonsai trees usually need as much light as possible.

And sometimes, even a south-facing window is not enough.

Thus, bonsai tree growers often invest in plant lights to give their trees an additional source of ultraviolet light in the winter months when days are shorter.

Reason Three: Not Enough Water

New bonsai owners underestimate the level of attention they need to pay to bonsai trees due to their shallow root system and pot.

While the shallow pot is necessary to keep the bonsai tree miniature, it also means that the soil and roots cannot retain as much water as a standard tree.

So, many bonsai trees will require daily watering.

Reason Four: Too Much Water

All bonsai trees are different, so you should treat them differently when it comes to watering.

Some bonsai owners make the mistake of watering their trees on the same schedule without checking whether the bonsai actually needs water that day.

To understand if your bonsai tree needs water, touch the top layer of soil. 

If your tree requires water, it will be dry to the touch.

Or, you can use a wooden stick to test the dampness underneath the soil.

To do this, place a wooden stick into the soil for five minutes. 

If it comes out wet at the bottom, the bonsai does not need water.

If it comes out dry, water your bonsai until water drips through the drainage holes at the bottom of the pot, then stop.

7 Common Signs a Bonsai Is Dying

Here are some of the most common symptoms of bonsai sickness and their causes.

Sign One: Drooping Branches

If your bonsai’s branches begin to droop, check to see how many limbs are affected.

If just one branch seems to be suffering, this is unlikely a health issue and is probably a sign that the limb needs better pruning to keep it from being weighed down. 

Or, that limb may also need better wiring to push it back into place.

However, if all the branches seem to be drooping, you probably have a mineral deficiency on your hands. 

So, try adding mineral supplements to your soil to see if your tree perks back up.

If the mineral supplements don’t work, the next culprit could be mold or mildew on the bonsai’s root system.

To fix this, you’ll need to remove the bonsai from its pot, search for the moldy or mildewed roots, and cut them away. 

You should also make sure the mold has not contaminated the soil.

If it has, you need to change the potting medium. 

Sign Two: An Unstable Tree

If your bonsai does not feel secure in its soil, or if it moves around easily when you disturb its pot, its roots may not be growing properly due to overwatering.

Strong roots will hold a healthy bonsai in place in a sturdy, solid way.

But, overwatered roots are weak and will eventually suffocate your tree.

Thus, try watering your bonsai less frequently to see if its root system improves and begins to take hold.

If this doesn’t work, your roots may need mineral supplements to grow healthy and strong.

Sign Three: Spots on Bonsai Leaves

Brown, black, and red spots on your bonsai tree’s leaves could signify a more extensive fungal infection in your bonsai tree.

You need to treat fungal infections swiftly, and it will likely require an antifungal treatment from your local nursery.

While you wait for the antifungal treatment to take effect, prune away all diseased leaves.

Sign Four: Chewed Leaves

Does it look like someone has been snacking on your bonsai tree’s leaves?

Unfortunately, that means a pest has probably made a meal and a home out of your bonsai tree.

Mites and aphids can infest a bonsai and quickly deteriorate its health.

You can try the natural route first by gently washing your tree’s trunk, branches, and leaves with gentle soapy water.

If that doesn’t help, look for bonsai tree pesticides at your local nursery or online bonsai supplier.

Sign Five: Wilting, Yellow Leaves

Often, the first sign that something’s amiss with your bonsai tree is that its leaves will begin to wilt and turn yellow or brown.

This common symptom can signify several different problems, though.

To determine what’s wrong, first consider your bonsai’s environment. 

Does it have enough light, for example?

If you can’t find an issue with the environment, isolate whether the problem could be overwatering, underwatering, or disease.

Address each of these possible causes one at a time so you can determine what is truly causing the leaves to turn yellow and wilt.

Sign Six: Injured Bark

Just like humans, your bonsai tree can suffer from skin issues that reveal themselves as swollen areas in the bark of the trunk or other unsightly injuries.

Usually, this is no reason for concern.

Injured bark is primarily the result of improper healing after pruning.

To fix this, prune trees toward the end of their dormancy when they can come back stronger and healed in spring.

Or, invest in some cut paste to assist the healing process where you’ve pruned branches.

Sign Seven: Losing Leaves During the Wrong Season

Many bonsai trees require a dormancy period in winter, where their leaves will naturally shed, and the tree will almost look as if it has died.

This process is natural and begins in late fall. 

It is not a cause for concern if you have an outdoor bonsai tree.

However, if your bonsai tree is losing leaves in spring or summer, your tree could be suffering from a fungal infection or moldy roots.

So, as soon as you notice leaves falling, remove the bonsai from its pot and inspect the root system for mold or fungus.

If you discover fungus, apply an antifungal treatment as soon as possible, as fungus is highly contagious and will quickly spread to the entire bonsai and possibly other nearby plants.

For mold, gently cut away the moldy roots. 

How to Tell if a Bonsai Tree Is Dead?

If you’re dealing with a bonsai tree that might be dead, but you want to know for sure, use this simple technique to check.

First, try scratching at the bark of a branch with your fingernail. 

If you don’t see any green beneath the bark, move closer inward toward the trunk and try again.

If the inner portion of the branch has green beneath its bark, the limb may be dying from the outermost tips. 

You should prune off that dead portion.

Yet, if you get all the way to the trunk and there is still no green, the entire tree is likely dead.  

Can You Revive a Dead Bonsai Tree?

Unfortunately, you can not revive a dead bonsai tree. 

Sadly, bonsai tree owners who have likely spent months or even years trying to raise a bonsai will have to face the fact that their tree is gone. 

But you can take the lessons learned from your past mistakes when you begin to care for a new bonsai tree.

If you believe your tree is not entirely dead, though, you may revive it by identifying the root cause of its issues and addressing them.

It will require patience and constant monitoring, but you can often revive a dying tree.

Final Thoughts

Bonsai trees are hardy yet sensitive, and they’ll usually give you outward signs when something is wrong with their health.

And by understanding those signs and their causes, you can usually rectify any issues before they become fatal.

So, pay close attention to your bonsai’s foliage, bark, sturdiness, and color to detect early warning signs that something is wrong.

You can almost always save a bonsai by paying close attention to its water, light, and fertilizer needs or by treating common issues like pests, mold, and fungus.

Bonsai trees can live with you well into old age if you give them proper care and attention.

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