March 13, 2021

How To Water A Bonsai

Bonsai trees are not like most other plants. So naturally, if you try to water them like other plants, especially house plants, they aren’t going to survive!

So how to water bonsai trees? Basically when the soil is dry, you need to water. You sould not water the leaves, only the soil and do not have a set routine. Let’s explore this more in depth.

How To Water Your Bonsai

But first, this doesn’t mean you can neglect them completely.

These two extremes are what make it seem like bonsai trees are hard to grow. But with this simple watering method, you’ll be able to give your bonsai enough water to thrive.

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How much water does a bonsai tree need? Keep a record!

One of the best pieces of advice I can give you to help your bonsai succeed and to help you get your watering schedule “just right” is to record when you’ve watered.

Knowing when you’ve watered last will help answer a lot of questions about whether or not it’s time to water again.

There’s a lot of great ways to keep track of this — pen and paper, excel spreadsheet, notes on your phone — but my favorite way is to use the BonsaiDo. It allows you to easily record each time you water, shows your watering history for each plant, reminds you when it’s time to water, and allows you to keep a photo history of the plant too.

There are a lot of different ways to use the app, but keeping track of watering has been a gamechanger for my bonsai trees!

How to Water Bonsai Trees (indoors and outdoors)

The best way to water bonsai trees is with the “soak and dry” method. Soak the soil completely then let the soil dry out completely before watering again. And make sure the bonsai trees are in a well draining soil in a pot with a drainage hole (more on that in a minute).

For indoor bonsais, it is generally best if water doesn’t get on top of the leaves. If it sits on a leaf for too long it can cause rot.

Use a small spout watering can or a squeeze bottle.

This isn’t as much of an issue for outdoor bonsai trees because there is more airflow and the water will dry out quicker.

Juniper Bansai Tree

If possible, just pour water onto the soil around your bonsai until it is completely soaked. DO NOT water your bonsai again until the soil has dried out — from the top of the pot to the bottom.

Bonsai trees do not like to sit in wet soil for more than 2-3 days.

So then comes the question…

How often water bonsai trees?

Bonsais should be watered only when the soil has dried out completely. There is no universal watering schedule that works for every bonsai in every climate.

Many indoor bonsai growers find that watering 14-21 days is a good frequency to keep their bonsais alive. Use this timeline as a starting point and adjust as needed.

The best frequency for watering your bonsai tree is whenever the leaves show very early signs of under watering.

Since most bonsai trees are very prone to rot with frequent watering, you’re best off to wait for a signal from your bonsai before watering.

But if nothing else, don’t water again until the soil is totally dry.

And remember, keeping track of your watering schedule is really important. I can’t tell you how many times I “think” I haven’t watered in a while, only to find out, thanks to my notes in the BonsaiDo app that it was just a few days ago.

Why does this watering method work?

Bonsais are generally native to areas where the soil drains quickly and water is heavy, but infrequent.

While your bonsai trees, especially indoors, don’t need a watering schedule this extreme, they will benefit from the “soak and dry” approach.

With a deep watering the bonsai has plenty of access to water. During the “drought” between watering, the bonsai will begin to grow new roots, searching for more water.

The soak and dry method helps the bonsai develop a large, healthy root system which will enable it to withstand longer periods of drought than most other plants.

DO NOT use a spray bottle for watering. Constant watering with small amounts of water, like with a spray bottle, will produce a weak root system that can’t withstand very long periods of drought.

That means if you don’t water for a couple days your bonsai tree will die. Or if you don’t get the water deep enough when you spray with a spray bottle, the bonsai will die. So don’t do it

Soak and dry… soak and dry…

The right soil is crucial for watering success

At the very beginning of the article I mentioned your bonsais should be planted in a well draining soil AND in a pot with a drainage hole.

Bonsai trees will quickly rot if they are in wet soil for too long. Ideally, your soil will be mostly dry, especially the top half of the pot, within 2-3 days.

So what makes a soil “well draining”?

I’ve dedicated a full post just to talking about the perfect soil mix for bonsai trees. You can read that here.

The short answer is a well draining soil looks “gritty” because it has ¼” (6mm) particles. ⅔ of the soil should be inorganic (rock) and ⅓ should be organic (pine bark, coconut coir, etc.).

What’s the best soil for your Bonsai

Traditional soil will not work well for bonsais It stays wet for much too long. I don’t generally recommend using most of the “bonsai and minature trees” soils found at most nurseries either. They tend to be too organic and still don’t drain fast enough.

If you’re new to bonsai growing or have killed a few bonsais from too much water, I highly recommend getting a bag of  special bonsai soil mix (organic and grit) for your bonsai. This is the best bonsai trees soil I’ve used. 95% (or more) of my bonsais are planted in this and they are thriving!

Beyond that, take a look at the soil post to get recommendations for other materials and how to modify other store bought soils to make them work better for bonsai trees.

Use a pot with a drainage hole

Another important piece of this watering method is using a pot with a drainage hole.

Remember how I mentioned bonsai trees don’t like to sit in wet soil for very long? It’s very difficult for the soil to dry out completely if your pot doesn’t have a drainage hole.

The hole in the bottom of the pot allows for excess water to flow out of the pot and away from your bonsai roots. It also provides another way for air to flow through the soil and help it dry out faster.

If you’re just starting with bonsai trees, a pot with a drainage hole is going to be extremely helpful for you.

How should I water the bonsai leaves or babies I’m propagating?

This is the one time–and the only time–that it’s okay to use a spray bottle for watering your bonsai tree–when you’re propagating!

However, even still… I recommend using a squeeze bottle to ensure the soil gets thoroughly wet.

When you’re propagating bonsai leaves indoors or outdoors, you can water them every day. You want to keep the soil damp (though not sopping wet) so the leaves have plenty of access to water.

Just spray the top of the soil with a spray bottle (or use the squeeze bottle). Like the roots of large bonsai plants, the leaves will absorb water from the air around them, so spraying the soil with a spray bottle is usually enough in my experience.

Keep an eye on your roots–they may dry out if they aren’t getting enough water.

Often I can look at the soil and know I need to water.

Other times, especially when I’m starting to reduce my watering frequency for these babies, I’m not sure if it’s time to water or not. Checking BonsaiDo app reassures me it’s time to water. Plus I can record photos in the app and see the progress of my babies too!

Watch your bonsai for indicators

Now that you know the soak and dry method, it’s time for you to give it a try!

Pay attention to the signs your bonsai is giving you. It will start to change if it needs more water or less water.

And lastly, when in doubt go without!

It is much easier to save your bonsai from too little water than from too much.

Share this post with your bonsai loving friends!


About the author 

Greg Reed

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