What Is Overwatering A Bonsai Trees?

Overwatering your bonsai can cause serious problems and even kill your tree, so it is important to know what it is and how it happens.

If you are doing things right, it shouldn’t even be a problem you have to worry about. A combination of good soil and correct watering will make sure you never have any issues with overwatering.

However, it is still good to have an understanding of what can actually happen so you can try to prevent it.

What Is Overwatering In A Bonsai?

Overwater is exactly what it sounds like, but at the same time it isn’t quite.

We are talking about a bonsai tree that is suffering from a sustained exposure to excess water over the long term.

The problem is slow to develop. You cannot overwater a tree once. People often get confused by this and panic if they add a lot of water at once. This is fine, this will not cause any problem.

The problem comes when you do this day after day.

If you over water your tree on any given day, the pot can only hold so much water. As the day goes on it will start to dry out and eventually need watered again. In a case of overwatering, the pot basically is never allowed to dry out; it is constantly being topped up with excess water.

A good way to think of it is like trench foot. Getting your own feet wet is fine, doing it for as whole day isn’t great, but it is still fine. The problem occurs when your feet are constantly wet for days on end. Tree roots are the exactly same. 

(You can read more information about What Do Healthy Bonsai Roots Look Like?) 

Why Is Overwatering A Bonsai Bad?

Basically overwatering can kill your bonsai, which we can all agree is pretty bad.

A tree needs two things to live, oxygen and water. Both of these are taken up through the roots. This is why we use free draining soil; it can provide the tree with a good balance of both.

If your tree is constantly sat in water, then this balance is off. There is plenty of water, but no oxygen.

The roots pretty much drown if your tree is overwatered. They can’t take in any oxygen as there is only water available to them. 

This results in the roots dying, which is of course is going to cause a lot of trouble for the rest of the tree. The roots are often seen as the engine of the tree, so once they are gone your tree is in a lot of trouble.   

As the roots are now dead, the natural bacteria in the soil will start to eat the dead roots and decompose them, which we know better as “root rot”.

If your tree is suffering from root rot, then it means it has been sat in water for a while and has gradually started to decline over time due to the excess water in the pot.

(If you think you have this problem, you can read more information about – How To Deal With An Overwatered Bonsai)

Factors That Increase The Chances Of Overwatering Your Bonsai

While having too much water in the pot is the obvious cause of overwatering, you will find that there are a number of factors that can really increase your chances of suffering this problem.

Poor Quailty Soil

If you have good free draining bonsai soil, you are never going to be able to overwater your bonsai. The excess water is always going to be able to drain away and your tree is never really going to be sat in water.

You could literally water your tree hourly and you still won’t be able to over water your tree, it’s just going to remain damp.

The real problem comes when your soil is not great.

If you soil doesn’t drain well, or it just holds a lot of water this can be bad news. The tree may not dry out properly in between watering and the then the tree may be sat in water for an extended period of time.

Poor Draining Bonsai Pot

I’ve just said you need the water to drain through your soil very well, but you also need the water to be able to escape from the pot.

The reason bonsai pots have holes in the bottom is exactly for this reason. Your pot needs good drainage otherwise the water is going to get trapped inside and your tree is going to end up sitting in water.

A proper bonsai pot shouldn’t really have any issues, but if you are using any other sort of pot then just make sure it has enough holes to allow the excess water to escape.

(You can read more information about Why Do Bonsai Pots Have Drainage Holes?)

Pot Size

The pot size isn’t the biggest factor that can cause over watering, but it can add to it at times. Usually the problem is when you have a very small tree in a very big pot.

Basically the roots only take up a small percentage of the pot and that means that when you water the pot, most of the water isn’t getting used up by the tree, since it’s too small. The tree is just surrounded by an ocean of water that it will never be able to use up.

If you have good soil and a well draining pot, this shouldn’t really be an issue, especially if you know how to water properly, you will find that the pot takes a long time to dry out and if you can manage for that, then it shouldn’t be an issue. If you do this right, a small tree in a big pot is actually going to grow very quickly and soon fill that pot.

This is also why you see people slowing increasing the pot size and uppotting to a bigger pots over time. They are trying to avoid the tree just drowning in excess wet soil. This is very common in gardening, but you need to remember that they tend to use soils that are more water retentive, like pure compost.

The Tree Isn’t Taking Up Water

If you tree isn’t taking up water, then the water you are putting in to the pot, isn’t getting used. This can very easily cause the excess water to build up and cause overwatering.

This usually happens over winter when your tree is dormant. If you are paying attention to your tree you may find that you do not have to water over winter, or if you do, it’s significantly less often.  

This usually isn’t a problem and your tree will be fine, but it is something to be aware of as if you continue to water like you did in the summer, you may start causing your tree to be too wet and starting suffering from overwatering.

Rain Can Cause Over Watering

Rain is something I deal a lot with and it can start to cause overwatering.  Rain is really just free water from nature, so if you have any of the above factors slightly incorrect, then rain is going to be a problem.

Personally I lived in London, which is pretty dry compared to Ireland. When I moved back here I suddenly found that my soil mix was not great for this climate. My soil had a little bit too much inorganic compounds, so was now holding too much water. This was fine in London, but a nightmare here where it rained a lot more.

You could argue that the soil was this issue, which is true, but the rain is still a problem. Of course in this situation the easier thing to fix is the soil, which is what I did, but you still need to be aware that rain will be adding water to your pot and can upset things.

Luckily I was able to notice this and I pretty much stopped watering completely and just let nature do it for me until the following spring when I was able to adjust my soil.

Had I not realised I would have had a lot of trees with root rot.

You and Your Incorrect Watering

Sadly you may be the cause of the overwatering. At the end of the day you are the one who is going to be providing the tree its water and if you get this wrong, then it’s you who has caused the problem. 

You are also responsible for the pot and the soil, so again, if you get this wrong, then you are the one causing the overwatering.

Luckily these things are all things you can change and manage properly. Even the things you can’t really control, such as the rain and a dormant tree, you can still manage them in a way that should avoid trouble, such as moving the tree to somewhere it will not get as much rain.

(You can read this article to learn – How To Water A Bonsai)

Conclusion

Now you should understand what causes overwatering and root rot, so hopefully you can avoid this happening.

If you think you may be suffering from this problem, then you can read my article that looks at signs and symptoms you may see on your tree and how to correct the problem 

(You can read more about – Frequently Asked Questions About – Watering Bonsai)