How Much Light Does A  Bonsai Tree Need?

Knowing how much light to give your bonsai tree can be confusing. This is made worse by the lack of information on the internet. I routinely see “5-6 hours a day” given as a rough guide to how much light a bonsai needs, but no real reason as to why this is the right amount.

While this amount is fine, it’s a bit more complicated than just saying this, which I will go through below so you can get a better understanding of what your trees might actually need.

How Much Light Does A Bonsai Tree Need?

If you are going to ask how much light a bonsai needs, then you are also going to need to ask what type of bonsai you have (its species) and what kind of light it will be getting.

These two factors can wildly change how much light a bonsai needs and is exactly why I am not a fan of the generic “5 or 6 hours”. Bonsai can not all be treated the same, so the level of light is going to change from tree to tree.

Is Your Bonsai Getting Its Light From Inside or Outside?

Honestly, your bonsai trees should most likely be outside. If they are, then you don’t really need to worry about this question in the first place. Just let nature do its thing. If your tree is outside it is going to get more than enough light.

If you are trying to grow your bonsai tree inside, the amount of light it gets is important and it can be very difficult to get this right. You really need your tree next to a window, which should give it enough light, but other factors like humidity and temperature can mess with your tree and cause it to struggle.

You can grow bonsai under a grow light, but this does not make it any easier. You can read my guide on – How To Grow Bonsai Using Grow Lights to see how I do it and how I decide how much light my trees need.

Light Levels Can Effect How Much Light A Bonsai Needs

We need to realise that there are two different ways to look at light levels. You have day length and you have direct sunlight.

Depending on where your trees are placed, or the weather, these two figures can be wildly different, which is why I think trying put a number on how much light your trees gets makes no sense. It’s too difficult to measure.

Direct Sunlight

This is literally the amount of the time that the sun is directly shining down on your bonsai tree.

This is the best kind of light for your bonsai tree, although at certain times of the year this can be too strong for some trees, but this will depend where you live and what species you are growing.

While this type of light is ideal it can change from day to day, especially if you live somewhere like I do where there are constantly clouds rolling through and blocking the direct sun.

This isn’t too much of an issue as the trees will still grow even when the sun is behind the clouds, but it is something to be aware of.  

Day Length

The other thing that can affect light levels is the day length. I live pretty far north and the change in day length throughout the year changes quite a lot. It changes from around 7 hours in winter all the way up to 17 hours of daylight in summer.

My bonsai trees are in a south facing position and can get direct sun for a large portion of the day. I would imagine on a good summer’s day they could easily get 10 hours of direct sunlight. 

They of course get a lot less light in winter, but you could argue this doesn’t even matter as most trees are dormant and don’t even have leaves, so they don’t even need any light!

However, it goes to show you that simply saying 5-6 hours makes no sense. This number can change so much dependant on the time of year and even the weather on a particular day.

Where You Live Can Effect How Much Light A Bonsai Needs

Where you live is of course directly rated to the above point about light levels.

The closer you are to the equator, the stronger the light will be and of course if you are like me, up in the far north, the light levels are just not great.

You can also argue that the further south you go, the better your other growing conditions will be too. Most trees generally like it a little warmer, so when you mix this with a better quality of light, you will get much better growth rates.

Species Can Effect How Much Light A Bonsai Needs

I think ignoring the species of a bonsai is very foolish, while 5 or 6 hours may be more than enough for one tree, you will find that some other species require a lot more light than others.

You also have many species that can grow in shade, which really means that they don’t need direct sunlight, they will grow just fine in normal day light, even if they are in the shade.

Native Trees

If you are using native trees for bonsai, or trees that can easily survive in your climate you don’t really need to worry about how much light then need.

Just keep them outside and nature will give them more than enough light. You should be more worried about their placement than how much light they are getting. (You can read more about – Where To Place Your Bonsai Trees At Home)

So long as you place them in a position where they can get some access to the sun they should be more than happy.

Tropical Trees

If you are growing tropical trees for bonsai, then you may want to be more interested in how much light they need.

You should really look up where they grow naturally and start to see what the day lengths are in these places, along with the amount of sun shine they may get and just generally what the weather is like in their natural habitat.

You then need to compare this to what you have and then decide if it is enough.

I have a lot of Mediterranean trees and I took the time to study the weather and light levels of some towns in this area. You can easily find this information on Wikipedia.

I was then able to see that what I have to offer here isn’t quite the same as what they would get naturally, which is why I have them growing under a grow light.

However, it is important to realise that while tropical bonsai may need more light than you can offer them, they will still survive. They just won’t thrive.

Just think about any ficus you have seen growing inside an office, or jade that is being used as a house plant. They can stay alive for years, but they are often long and leggy and just not looking in the most ideal shape.

I’ve grown tropical plants on the windowsill and they have grown very slowly, but been happy enough. I’ve then put them under a grow light and given them conditions that are more like their natural climate. Within days the increase in their growth rate is visibly noticeable, they really start to thrive.

How Much Light Is Enough For A Bonsai?

As you’ve probably been able to work out already, there is no ideal number for how much is “enough” …Just give them what you can. If your tree is growing and it’s healthy, then that is all that matters. 

As I’ve already said you really only need to worry about this if you are trying to grow tropical trees out of their natural environment and even then you will be surprised how your natural light levels can be enough, it’s really only the cold weather you have to protect them from.

Trees Need Darkness

I think it is also important to note that trees do need a period of darkness too. You cant just give them 24/7 light and expect great growth.

Tress grow in nature so they expect some form of darkness everyday, it actually keeps them healthy, so dont try and avoid this.

Conclusion

Worrying about how much light your tree needs isn’t worth thinking about.

Just put them in the sun and let nature do its thing. You should focus on trying to worry about the factors that you can control, such as using good soil and watering correctly. 

You are going to be able to sort these things out and your bonsai will be more than happy with the amount of sun light you get in your area.