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When Should You Water a Bonsai Tree? Don’t Follow the Calendar — Check the Soil

Watering is one of the most important parts of bonsai care, but it is also one of the easiest things to get wrong. A common question from new bonsai owners is:

“How often should I water my bonsai?”

The answer is surprisingly simple: don’t water your bonsai on a fixed schedule. Water it when the tree needs it.

As demonstrated in our video, different bonsai can dry out at very different speeds, even when they are sitting next to each other.

🌱 Check the Soil Before You Water

Instead of deciding that your bonsai needs watering every day, every two days or once a week, check the growing medium first.

Use your finger to feel the surface and just below it.

If the soil is still clearly moist, the tree usually doesn't need watering yet. If the surface is beginning to dry and the substrate below is only slightly moist, it is normally approaching the right time to water.

With free-draining bonsai substrates such as Akadama, pumice and lava rock, you can often also see a change in colour as the substrate dries.

The important rule is:

Check daily — but only water when required.

💧 Why Two Bonsai May Need Water at Different Times

In the video, we can see several bonsai growing side by side. It would be easy to assume that because they experience the same weather, they should all be watered together.

Not necessarily.

How quickly a bonsai dries depends on many factors, including:

• ☀️ Sunlight and temperature
• 💨 Wind
• 🌳 Tree species and foliage density
• 🪴 Pot size and depth
• 🌱 Type of bonsai substrate
• 🌿 Root development
• 📍 Position in the garden
• 🌦️ Recent rainfall and humidity

A small bonsai in a shallow pot can dry considerably faster than a larger tree in a deeper pot. One tree might therefore need water while the bonsai beside it is still sufficiently moist.

Treat each bonsai individually.

🚿 How to Water Your Bonsai Properly

When your bonsai does need watering, don't simply give it a small splash.

Water the entire surface of the substrate thoroughly until water runs freely from the drainage holes underneath the pot. This helps ensure that the whole root system receives water rather than only the upper layer.

For very dry or highly free-draining substrates, watering thoroughly and then going over the tree again shortly afterwards can help ensure the root ball has been properly wetted.

Good drainage is extremely important. A quality bonsai substrate should allow excess water to escape while retaining enough moisture for the roots.

⚠️ Don't Keep Bonsai Permanently Wet

Many beginners are understandably worried about allowing their bonsai to dry out, but constantly watering an already-wet tree can create another problem.

Roots need both water and oxygen.

Keeping the growing medium permanently saturated can reduce the amount of oxygen available around the roots and may contribute to poor root health.

The aim isn't to keep the pot constantly soaking wet.

Think instead:

Water thoroughly → allow the substrate to begin drying → check again → water when required.

☀️ What About Hot Summer Weather?

During warm, sunny and windy weather, bonsai can dry extremely quickly because they have relatively small pots.

In summer, you may need to check your trees more than once a day, particularly small bonsai and trees in shallow pots.

Some trees may require daily watering during hot weather, and occasionally more than once per day under particularly demanding conditions.

That still doesn't mean automatically watering every bonsai twice a day. Check them first.

During cooler periods, the same tree may remain moist considerably longer.

🌧️ Does Rain Mean You Don't Need to Water?

Not always.

Light rain can wet the foliage and the very top of the substrate without thoroughly soaking the root ball. Dense foliage can also prevent some rain from reaching the pot.

After rain, check the substrate rather than assuming that the tree has received enough water.

🌳 The Golden Rule of Bonsai Watering

There is no universal answer such as:

❌ “Water every two days.”

❌ “Give it one cup of water.”

❌ “Water every Sunday.”

A much better routine is:

👀 Observe → ✋ Check the substrate → 💧 Water thoroughly when needed.

Once you get into the habit of checking your bonsai regularly, recognising when it needs water becomes much easier.

Quick Bonsai Watering Guide

Check your bonsai every day.
🌱 Feel the substrate rather than relying on a timetable.
💧 Water when the substrate is beginning to dry.
🚿 When watering, soak the entire root ball thoroughly.
🪴 Make sure excess water can drain freely.
☀️ Check more frequently during hot or windy weather.
🌧️ Don't assume rainfall has fully watered the pot.
🌳 Remember that every bonsai can have different watering needs.

The best watering schedule is no fixed schedule at all — let your bonsai and its soil tell you when it's time.

Bsoil Plants — helping bonsai enthusiasts grow healthier, stronger trees.