How To Water A Bonsai

Watering a bonsai is one of the most important factors in keeping it alive.

Watering is also a balancing act …Too little and the tree dies …Too much and the tree can also die.

Watering should be a fairly easy process, but this balancing act can often get confusing for beginners and can cause them a lot of unnecessary concern.

Getting the balance right is a tricky skill to learn but luckily with a bit of patience it can be easily mastered and I will go through exactly how you can teach your self this vital skill.

(If you are away form home for a while, you can read – How To Water While On Holiday)

When To Water Your Bonsai?

When learning HOW to water a bonsai, the first thing we need to do is be able to identify WHEN the bonsai tree needs water.

I often see people teach that you should water your bonsai trees water everyday. This is wrong. You should not water on a schedule like this.

However, you should check if your bonsai tree needs water every day.

“Checking” is different from actually “doing”. 

Basically you should be assessing the bonsai trees needs daily. If you find it needs water ..Give It Water.  It’s that simple. Blindly watering everyday is never going to work and will affect the health of your tree in the long run.

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

How Do We Access If A Bonsai Tree Needs Water?

Firstly we need to know the different factors to take into consideration when trying to work out when a bonsai needs water.

The following points below can all cause your tree to need water and these can constantly be changing, making it quite tricky to work out if your bonsai tree needs water or not.

The Soil You Are Using

What type of soil is your bonsai tree in? Certain soil mixes will hold more water than others and some will dry out faster.

Exactly how long the bonsai soil holds the water may also differ based on the components it is made from.

(You can read more information on – A Guide To Bonsai Soil)

The Pot Size

The size and shape of your bonsai pot will also determine how much water your tree has. A bigger, deeper pot will stay wetter longer than a very small shallow pot.

Of course this is also linked to soil, the pot will be filled with soil and sometimes the more soil you have, the longer it will hold water.

Temperature

The hotter it is, the faster the soil will dry out, as well as the fact that the bonsai tree is more likely to use more water when it’s hot.

Humidity

The humidity of the air also affects how quickly a pot and the soil will dry out.

Light Levels

Light can also effect how quickly the pot dries out.

It can be argued that the more sunlight a surface gets, the hotter it gets, so it’s more temperature related. This is true, but if light increases the temperature, then how sunny it actually is, can be important.

Trees also photosynthesize in light and this will require water. This means that high light levels can cause the tree to use more water and cause the pot to dry out faster.

The Species Of The Tree

Certain species of tree will use more water, faster than others. You will find certain trees will just need water sooner than others.

The Growth Rate Of Your Bonsai Tree Matters

The rate at which a tree is current growing will also affect how much water is needed.

A tree will use more water during the growing season compared to when it is dormant over winter.

(You can more about – How Trees Grow Through The Season)

Putting All This Data Together To Work Out When We Can Water A Bonsai

As you can see there is a lot of factors we can use to work out if a tree needs water and of course these factors can be changing all the time, which is why it is something you need to be checking daily.

Putting it all together really just means asking yourself a lot of questions about the tree and trying to work out if it might be in need of water of not. Some of these questions you don’t really need to ask every time, as you will start to get a feel for things.

For example if you have a willow, you will just know this species like a lot of water compared to something else.

However, One of the first things to ask yourself is when was the last time you watered your bonsai?

Then ask yourself what the weather has been like since you last watered? Has it been overly warm and sunny? Has it rained non stop? Has it been humid?

These should give you some clues to what state of dryness your pots might be in and with experience you will start to get good at predicting how wet or dry things will be.

Start to pay attention to these small changes in the local climate every day and you will start to learn how the weather affects your trees.

Does your Bonsai Look Dry?

A very easy thing to do is visually inspect your pot. Look at the soil …Does it look dry?

Do you know what your soil looks like when it is dry? When I first started I had a spare pot that I just filled with soil. It was bone dry. I was able to look at the colour of it and compare it to the soil around my trees. Then after watering I compared it again so I could tell the difference from 100% watered and 100% dry soil.

 I was very quickly able to work out how wet my soil was from just looking at it after doing this for a while. 

Lift Your Pot Up To Feel The Weight

This is similar to what I’ve just said above about looking, but this is based on feel.

In my early days of bonsai I would pick each tree up and move it before watering (this only works with small trees, you can easily pick up). 

When you do this, make a conscious effort to feel the weight of the tree. 

Now water your tree and move it back to where it should be. As you place it back pay attention to the new wet weight. This should be your tree at its heaviest.

After a while you can pick up a tree and feel if it needs watered or not. It will feel very light compared to how you would expect it to feel when its fully wet.

Stick Something Into The Soil To Test For Moisture

A very good way of checking if your bonsai tree needs watered is to stick something into the soil. You will often see people suggesting to stick your finger into the soil, about an inch deep.

This might be good for a big tree in a big pot, but it’s not a good idea for a small tree. You will also often hear to put a wooden chop stick in and then pull it out.

I personally think this is better than your finger.  If I am ever doing this I actually prefer to use a cocktail stick. They are just smaller and cause less disruption to the soil and tree.

All you need to do is stick it in and pull it out and you will be able to see if the wood is wet of not.

This technique is really good as its takes a reading from the center of the soil. The surface might appear dry, but actually, underneath the soil might still be very damp.

Your Bonsai Will Tell You It Needs Water

If your bonsai tree needs water, it will start to tell you. It will start to show some clear and obvious signs that it is in need of water.

The first sign is the leaves will wilt. This is really noticeable and if you look at your tree and everything is wilted, water it immediately. You will find that the leaves plump back to normal rather quickly. Usually after an hour or so.

If you miss this sign, the tree will continue to dry out and its leaves will then start to fall off. This will usually be nearly all the leaves at once. If this happens your tree is in a lot of trouble. If you act quickly you can hopefully save the tree.

Water it immediately and do not let it dry out again. Hopefully after a few days or even maybe a few weeks, the bonsai tree will grow new leaves.    

If you wait too long, the tree will die and cannot be saved.

(You can read more about – What Should You Do If You Accidentally Underwater A Bonsai?)

How To Actually Water A Bonsai

The most effective way to water is a bonsai tree is to get the water to flow through the soil.

This means you need to water from the top and the water needs to come out the bottom of the pot.

As the water travels down through the pot, it sucks in air along with it. This air is really important as the tree will use this air. This is why a good free draining bonsai soil is so important.

All those little air gaps in the loose soil are literally filled with air that the tree uses. The more air and water a tree has, the faster and better it will grow.

Using A Hose/Watering Can

It is best to use a hose or a watering can for your bonsai.

This will allow you to water the surface of the soil in a way that will let the water pass through the pot from top to bottom. Any hose or watering can will work, but the finer the rose the better (the rose is the bit where the water comes out).

If you can get a rose with lots of holes, it will make the water finer. Finer water is usually more gentle when it lands. This is important as you do not want to wash away your bonsai soil from the top of the pot.

Be careful with a hose that has a strong water flow as it can be very easy to wash away your bonsai soil.

(You can read more about – What Watering Tools Can You Use For Your Bonsai?)

Misting A Bonsai Is A Waste of Time

Misting a bonsai is not needed.

Some tropical trees enjoy misting as it keeps the humidity up and can help with the formation of aerial roots.

However, For a non-tropical bonsai tree, misting is not necessary and doesn’t do much for the tree. The majority of water is taken up by the roots, so just water the roots.

Dunking A Bonsai Tree In Water

This can be done, but it should be avoided.

It is suggested that if your bonsai tree is bone dry you can dunk it in water and let it sit so it becomes fully hydrated. This will work, but you are better just using a hose or watering can and repeatedly watering it over a few hours to ensure it is thoroughly watered all the way through.  

Dunking a bonsai tree fully in water can actually compress the soil and if you use a loose mix like mine, the bonsai soil will actually wash away when it is fully submerged.

Does The Time Of Day You Water Your Bonsai Matter?

This question has been argued about by gardeners since the first plant was ever grown. Some say early in the morning is best, others say at the end of the day is better. Honestly I have no idea.

There is an argument that the fact that trees close their stomata at night, which is basically little vents in the leaves, so its better to water in the morning when these are open and they can take in water …but as I have already mentioned, you water the soil, not the leaves, so if these are open or not is irrelevant.

I think you just need to pick a time that works for you and stick to it.

I personally water my trees at about 11am. I have scheduled this into my routine, so each day I set time aside to check on my trees.

I am at the point where I know my trees very well. I know roughly how long they can go in between watering. As I am writing this, it’s the middle of winter. I watered my indoor tropical bonsai trees yesterday. I know they can go about 48hrs at this time of year. Today when it reaches 11am, I will not do anything, I know they are fine… well I might just check on them anyway as I like to look at them, but I know already that they shouldn’t need watered.

My outdoor bonsai trees are in a totally different situation. They seem to stay wet for longer due to the amount of rain I get. The rain waters for me. I still check regularly, especially if its been dry, but the amount I watering I do in winter is very small.

In the summer this will change. I probably will need to water them every day. If it’s especially hot, I might check on them twice a day and in some cases, I might even water twice a day. It really depends.

I do exactly as I described above, I take a lot of factors into consideration, I also check what my trees are looking like, then I make my decision based on that.

So long as you are consistently checking your trees at around the same time each day you will start to learn how much water they need and how often they need it.

What Type Of Water Should You Use On Your Bonsai?

This is another hotly debated topic. It is said rainwater is the best, which is probably true.

If you can’t collect rain water, tap water is going to be fine. It is best if you can leave the tap water to sit for a while. 

This will do two things. It will bring the water up to room temperate and it will also allow any chlorine to evaporate. I like to refill my watering bottles immediately after I use them, that way they will sit for about 24hrs before I use them again.

(You can read more about – What Kind Of Water Should You Use For Your Bonsai?)

Your Watering Will Always be Changing and You Will Always be Learning

The skill of watering a bonsai is not one that is mastered after a while, and then you are done. Your bonsai trees will always be changing and so you must always be learning.

As the seasons change, the will tree gets more leaves, and get more roots and eventually it will become root bound, these factors will all affect how much water they need and how often.

The same goes for when you repot. A hard root prune and new soil will totally change how that bonsai tree behaves. The frequency and amount of water needed will totally change after a repot and you need to be ready to adpt to this.

(You can read more about – How To Water A Bonsai After Repotting)

The good thing is that the longer you do this, the quicker and better you become a being able to read the changes in the trees behaviour. You will be able to adjust your watering accordingly without any problems, you will just know how to read the tree and give it what it needs.

(If you end up watering to much, this can be a problem, you can read more about – What Is Overwatering A Bonsai Trees?)