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How To Tell If A Bonsai Tree Is Dead

How To Tell If A Bonsai Tree Is Dead
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At some point in time, all bonsai owners have a tree that is struggling. Whether it's been left with a neighbor to water while you're on holiday, or it's suffered some kind of disease, there can be many reasons that your bonsai can die.

While most cases are a lost cause, there are some situations where good horticulture can bring your tree back from the brink. So let's look at how to tell if a bonsai tree is dead, so you can work out whether you're nursing a tree back to health or simply watering some firewood.

What does a dead bonsai tree look like?

A dead bonsai tree will look like this:

  • Yellowing foliage
  • Browning foliage
  • Dry/crispy foliage
  • No new growth
  • Buds turn black
  • The tree stops using water

We've all seen a dead tree before, so when your bonsai has been dead for a long time I'm sure it will be simple enough for you to recognize. However, when a tree has died recently it may take several weeks or months for any strong changes in appearance, so it is helpful to know about the early signs of a dead bonsai and when they start to show.

There are a lot of variations between different bonsai species so it wouldn't be practical to go through them all here, but let's consider deciduous and coniferous trees separately as they can show signs of death quite differently.

Signs of death in a deciduous bonsai tree

Deciduous trees move much more water through their system when compared to conifers. They have bigger leaves with a thinner cuticle, which allows them to transpire at a higher rate.

Increasing the rate of water movement through their system allows deciduous trees to generate energy more quickly through the growing season. This is important because they shed their leaves over winter, so they need a big store of energy to re-grow their canopy next spring.

A high rate of water mobility makes deciduous trees more vulnerable to drought. It also means they show signs of death sooner than conifers because they dry out much faster.

Some deciduous trees move water very quickly (Japanese maple and birch, for example), while others move water more slowly (such as cotoneaster or Chinese elm).

Trees that move water more slowly can sometimes be evergreen, and won't lose their leaves over winter. This is common in some varieties of cotoneaster bonsai or Chinese elm. Whether a tree is an evergreen can also depend on its environment, where a tree grown in a warmer climate will be less likely to drop its leaves before winter.

If you have a broadleaf tree that doesn't lose its leaves over winter, leaf loss can be a sign of death. However, it may just be the tree adapting to a change in environment or struggling with a health issue, so make sure you are applying good horticultural techniques to look after the tree and it may well come back next spring.

The earliest sign that a deciduous bonsai is struggling will be wilting of the leaves. This happens when they do not have enough water in them and they start to deflate like a balloon.

They can then start to show browning or yellowing of the leaves, which will ultimately dry out and become very crispy. This can happen over a matter of days in some cases.

You may also notice a color change in the stems of young growth, which will become hard and brittle.

If you notice any of these signs on a deciduous bonsai you need to take immediate action, but more on that later.

Dead pine bonsai

Signs of death in a coniferous bonsai tree

Conifers do not move water nearly as quickly as deciduous bonsai, so they can take a long time to show signs of death.

The most common feature that people notice in conifers is a color change in the foliage, but unlike with deciduous trees, this can be very subtle at first.

Foliage may just lose the vibrancy of its green and become duller. This is a sign that a branch or tree is dying, but can also be a feature of milder pests such as spider mites.

This difficult to spot but early sign of a tree in trouble can help you identify and treat any health issues early, potentially saving the tree.

After greying, the foliage will continue to become more yellow or brown and start to become dry and crispy, similar to a deciduous tree.

This happens much more slowly on a coniferous bonsai, usually over months. If you find one of your bonsai has turned yellow or brown all over, it has likely been dead for months and is now a lost cause.

One further feature to look out for in some species of conifer is the dieback of specific branches. Some trees, such as junipers, have vein-specific resource flow from roots to foliage. This means one root will support one or more branches, and if that root is lost then those branches will die.

If you have recently repotted and root pruned the tree, then that would probably be the cause of a lost branch, however, if you unexpectedly lose a branch on your bonsai it may be a sign of root rot, which can be very serious if it isn't treated quickly and decisively.

A final note on deciduous conifers such as larch. They lie somewhere between conifers and deciduous bonsai, but will generally show signs of foliage death quite quickly as they move water quite rapidly.

Bonsai scratch test

If you have a tree you are worried about, you may want to try the scratch test to help you work out if your bonsai is dead.

The basis of the test is that beneath the tree's bark lies the cambium layer. In living trees, this is green and moist. In dead trees, this will be brown and dry.

You simply need to scratch away some of the bark to see if you can find some green underneath. It's best to first try this in an obscure part of the tree rather than the middle of the trunk because if your tree is alive you don't want to be left with a scar there.

If you scratch and see brown, be sure to try in a few more locations because some branches may be dead but there is still life in the tree elsewhere.

It's important to remember that this test only gives you a rough idea of where the tree is now, and not whether it will live or die. A tree you think is likely dying might be green on the scratch test but end up dying anyway, as many of them are too far gone by the time you start worrying about them.

When is a bonsai tree dead?

A bonsai tree is considered dead when there are no longer any living cells capable of generating new growth. This can mean different things for different species.

A deciduous bonsai will generally be capable of growing back new foliage if you totally defoliate it. This is indeed a common technique to increase branching and ramification but can be risky if performed without adequate insight or on an unhealthy tree.

Conifers on the other hand need some foliage to keep growing. If you remove all foliage from a Juniper branch, for example, the entire branch will die. This is how we create new deadwood. If you do this across the entire tree, then the tree will die.

Conifers rely on foliage at branch tips to draw enough water through their branches to move resources for growth. Deciduous trees, on the other hand, can survive without their leaves for a time. They generally have a much thinner bark that will transpire more water and can even generate small amounts of energy through photosynthesis.

So if your coniferous bonsai has lost its foliage for any reason, it's probably not going to be saved. Deciduous trees, on the other hand, have very good potential for bouncing back if the cause of their foliage loss is addressed.

Why is my bonsai tree dying?

There can be many reasons that a bonsai tree is dying, but I'm afraid to say that in the majority of cases the root cause is bad care from the owners. This isn't to make you feel bad (we all start somewhere), but actually is good news, because if you identify the cause early enough you can stop your bonsai from dying.

Watering problems

The most common cause of death in bonsai trees is poor watering. Good bonsai watering practices are not difficult, but if you have never been told what to do when watering your tree you may be causing it problems.

Bonsai can suffer when they are overwatered because there is not enough air in the root system. This is usually due to applying water too regularly to a tree planted in soil that is too organic. If your tree's roots are never allowed to dry out and you water on a schedule, this may be the reason your bonsai is dying.

On the other hand, a bonsai can die quickly when it does not receive enough water. This is common when trees are left with friends over a vacation, or if bonsai are cultivated indoors when the species should be grown outside, but can also happen to very attentive and caring beginners who are only sprinkling a small amount of water at a time.

A single episode of underwatering can cause widespread root and foliage death in a bonsai tree. You may not notice the effects for days or weeks, but they are irreversible. The good news is, if the tree survived and you water appropriately from then on, it has every chance of recovery in the long term.

The same is true for overwatered bonsai trees. By correcting your watering practices, you give the tree a chance to rebuild its root system and become a thriving bonsai again.

Spruce bonsai dying from aphids

A spruce bonsai that has had massive needle casting due to a green spruce aphid infestation. Note the banding on the discolored needles.

Diseases

Diseases such as root rot in bonsai can be the cause of a dying tree. This is most often a result of overwatering but can occur spontaneously if contaminated soil is used. It may also be spread on the feet of fungal gnats.

Fungal diseases of the foliage may show similar signs of tree death, such as yellowing or drying of the foliage, but usually, they will not affect the entire canopy.

Most severe fungal diseases indicate a problem with the roots of your bonsai, as they are the epicenter of health in the tree. Consider applying an anti-fungal spray to prevent further spread and make sure you are watering well. In particular, avoid watering the foliage because this can spread the infection.

Damage from humans

In the styling of a bonsai tree, it is relatively easy to cause trauma to the tree that can cause the death of a branch. This will result in the same foliage signs as mentioned above, but they will be localized to a single branch of the tree.

The biggest cause of bonsai death as a result of human intervention is repotting. Repotting is like open-heart surgery for your bonsai. It is an essential operation that will add years to the life of your tree, but if you perform it recklessly or without a plan it can be fatal.

The reasons a repot may result in the death of your bonsai include:

  • You removed too many roots, and the tree couldn't recover.
  • You failed to secure the tree properly in the pot, and the subsequent movement of the bonsai within the pot prevented the growth of new roots.
  • Your aftercare following the repot was poor. This may include overwatering, leaving the tree out in the rain or wind, or exposing the bonsai to too much sun.
  • You repotted a bonsai that was already weakened from a heavy styling or that was suffering from a disease.

What to do if my bonsai is dying

If your bonsai is on death's door, there are some do's and do not's that you can use to give it the best chance of recovery.

First of all, focus on watering. This means accurate watering, not over- or under-watering. Let the first half-inch of soil dry out, then thoroughly drench the rootball. This gives the best balance between water and oxygen for your tree to regenerate its root system.

If your tree has been overwatered, or you live somewhere with a lot of rain and you can't get the tree under cover, then you should prop up one side of the pot with a wooden block so the pot is on an angle. This increases the gravity column working on the water in the pot, forcing it out of the pot more quickly.

If your tree has a specific issue, such as a fungal infection or root rot, then you need to treat the specific cause. This is usually secondary to good watering because it can't be over-emphasized how important that is for your tree.

It is very important to remember that you should never fertilize a sick bonsai tree. Fertilizer is a growth stimulant to be used in healthy trees, but the high salt content and nutrient content that they contain can be toxic to a struggling root system.

You should also resist the urge to jump into a repot. As mentioned above, repotting a tree is a traumatic process. It can sometimes be helpful if you are within the safe repotting window (early spring before growth has started) and you know the cause of the tree's health issues are down to the soil it is planted in, but otherwise, you will better serve the tree by watering it accurately and giving it the time to heal itself.

What to do with a dead bonsai tree

If you noticed the warning signs too late and your tree died then don't beat yourself up, it happens to all bonsai tree owners at some point.

The best thing you can do with a dead bonsai is to learn from it. Analyze what you think went wrong and how you could have handled things differently. Take that information into the garden and apply it to your other trees, hopefully preventing them from suffering the same fate.

If your bonsai died of a disease or a fungus such as root rot, you should get rid of it as soon as possible, ideally by burning it. Make sure it doesn't have a chance to spread to the rest of your bonsai collection or any of your landscape trees.

Finally, if you're happy there's no risk of spreading infection and the tree has an interesting structure, you may want to consider using it for tanuki. This is where a living tree is grown around a dead one, blending the two so they look like one entity.

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