If you have ever looked at a bonsai pot you may have wondered why they have so many holes in the bottom.
Basically they are for drainage, which help keep your root ball healthy. Bonsai pots are pretty small and shallow, so it’s important that we use this small space as efficiently as we can in order to keep our trees healthy.
What Are Drainage Holes On Bonsai Pots?
On a simple level they are just holes that allow excess water to drain out.
If you look at it a little deeper you will realise they are hugely importantly for the health of your bonsai tree.
When you are watering your tree the water is going to hit the soil surface and start moving through the pot. This is of course going to give the tree the water it needs, but it actually gives tree oxygen too.
As the water moves down through the pot and out the drainage hole, it actually sucks in air behind it.
Having a drainage hole basically allows for this airflow, which is exactly what it needs. When you couple this with loose soil, which has plenty of gaps for this air, then you have the recipe for a very healthy root system.
Bonsai is all about balance. You need the balance of the pot and soil to work together to allow for optimum levels of air and water, which in turn will give you optimum growth and health. The drainage holes are just one part of this system.
Don’t You Want Water To Stay In The Bonsai Pot?
If you are new to growing plants, it may seem very counterproductive to water a bonsai and see all the water you just added pouring out the bottom.
I am sure you are thinking that you need the water to stay in the pot, so the tree can drink it.
This is true, but it actually only needs enough to just dampen the soil, It doesn’t need to be soaking wet.
The drainage holes allow you to water as much as you want and the excess will always escape, meaning that the bonsaisoil will just be left damp.
As I’ve already mentioned above, so long as you have good bonsai soil, then you will have a better balance of water and oxygen, which is what you need for your tree to be healthy.
What Happens If You Do Not Have Drainage Holes?
If you have no drainage holes, then the water cannot escape from your pot. This is going to end up with your tree being sat in water. Over time this excess water can actually damage your roots.
Too much water will cause root rot, and if you have no where for the excess water to go, this is going to happen very quickly. (You can read more about Root Rot In Bonsai (What Is It? and How To Fix It))
You could argue that you could water less, which would work, but trying to get this right balance of water corretis going to be extremely difficult, as well as the fact the air flow in the pot is not going to be great.
If you are using a pot that does not have any drainage, you need to change that as soon as possible. Either add some drainage holes to the pot, or use a different pot.
Why Are The Drainage Hole So Large On Bonsai Pots?
You might have noticed that some bonsai pots have rather large holes, this is just to allow as much water as possible to escape. The bigger the hole, the easier water can escape.
It also allows for the water to escape quickly, the faster water can get out, the faster air can get sucked into the pot, which is exactly what you want.
Bonsai pots are also quite small and very shallow, so it is easier to make a large hole, rather than try and make the bottom of the pot less flat.
You will find in some larger pots, that the bottom does slopes down towards the hole to help drainage.
This isn’t possible in every pot, whereas making a larger hole is easily done.
Why Do We Use Mesh On The Drainage Holes?
If you have ever seen good bonsai soil, you will very quickly understand why we use mesh.
The soil particles are very small and of course the holes are pretty large. Basically if we did not use some sort of mesh, the soil would just pour straight out of the bottom.
All the mesh does its keep the soil in the pot, while still allowing water to escape.
You will find in some plastic bonsai pots that the holes have a built in mesh over them. This is easy with a plastic pot, but not so simple with clay, which is why clay pots just have a hole that you will need to cover yourself.
What Are The Other Small Holes For?
If you look carefully on some bonsai pots you may notice some smaller holes, usually around the larger drainage holes.
These are actually for wire. This just allows you to easily and tidily feed wire up into the pot so you can tie your tree into place and anchor it to the pot.
These are normally found on larger pots, but not always. It doesn’t matter if these are not here. You can still feed the wire through the larger drainage holes. Both techniques work equally as well and do exactly the same job.
Drainage holes are often something we don’t pay any attention to, but they are actually pretty important when they come to bonsai.
They actually help keep our trees healthy and are something we should be thankful for. If your pot hasn’t got any, you need to change that quickly.
The sooner you have proper drainage the sooner your tree can have the right balance of water and oxygen and start growing more healthily.