How to Water a Bonsai: When, How Often and With What

Watering a bonsai sounds simple: add water, done. Yet watering mistakes are the most common reason a bonsai dies. That is because of the small pot: there is little soil to hold water, and depending on the weather it can dry out in a single day or take a whole week. Here you will learn how to water a bonsai properly and how to tell when your tree is thirsty.

No fixed schedule: check first, then water

The most important rule: don't water by the calendar, water when the soil needs it. How fast it dries depends on pot size, soil, species, position and weather. A small pot in summer sun often needs water every day, while the same tree in winter may only need it every few days.

How to check if it's time:

• Finger test: Push a finger about 1 cm into the soil. If it feels slightly dry at that depth, water. The surface alone is often misleading.
• Wooden chopstick: Push a wooden chopstick deep into the soil and pull it out after a few minutes. If it is dark and damp, wait. If it stays light and dry, water.
• Weight: Lift the pot once right after watering and remember how it feels. If it is clearly lighter later, the soil is dry. With a little practice this works surprisingly well.
• Soil colour: Wet soil is darker than dry soil. Akadama in particular (the typical granular bonsai soil from Japan) turns visibly lighter as it dries.

How to water properly

When you water, water thoroughly. Use a watering can with a fine rose so the soil is not washed away. Pour slowly over the whole soil surface until water runs out of the drainage holes. Wait a few minutes and water a second time. The reason: on the first pass, dry soil often only gets wet on the outside while the inside of the root ball stays dry. The second time, everything soaks up properly.

Afterwards, don't leave water standing in the saucer. Roots that sit in water all the time get no air and rot.

If water runs through unusually fast or pools on top, the root ball is often too dense. That's a sign it's time to repot.

Immersion: when it helps and when it doesn't

For an immersion bath, you place the whole pot in a bucket or basin until the soil is under water. Once no more air bubbles rise, the root ball is full. Then lift it out and let it drain well.

• Useful: when the soil has dried out completely and water just runs off, or for small indoor bonsai you can easily bathe in the sink.
• Not useful: as a permanent routine or for hours. The tree must not be left standing in water. For species that like to dry out, such as the jade plant, normal watering is enough.

What kind of water?

Rainwater is ideal because it is soft and has no additives. Tap water is fine too for most trees. Very hard water slowly leaves white crusts on the soil and pot. That looks untidy but does little harm to most species. The exception: lime-sensitive trees such as the Satsuki azalea should get rainwater whenever possible.

Summer heat and holidays

In midsummer, small pots outdoors dry out very quickly. Then you may need to water once or twice a day, sometimes even more on hot days. Check in the morning and late afternoon. A spot with shade during the midday heat saves a lot of water.

For holidays:

• One or two days: Water thoroughly and move the tree to a bright but shaded, sheltered spot. That is often enough.
• Longer: The safest option is a person who waters. Show them once how it's done and explain how the soil should feel. In summer, a single forgotten day can be enough to lose a bonsai.
• Watering systems: If you use one, test it for a few days before you leave.

Winter: outdoors and indoors

Outdoors, most trees barely grow in winter and need much less water. Still, the root ball must not dry out. Water on mild days, ideally in the morning, so the water drains before the night frost. If the soil is frozen, don't water: the water can't get in. Trees under a roof or in a shelter get no rain, so keep a close eye on them.

Indoors, heating dries the soil faster than you might think. At the same time the tree grows more slowly. So the rule is the same: just keep checking.

Too much or too little?

Too much water	Too little water
Soil is constantly wet	Soil is bone dry, pot feels light
Leaves turn yellow, often the lower ones first	Leaves droop, then turn dry and crispy
Leaves drop although the soil is moist	Leaves drop after wilting
Musty smell, mould on the soil	Soil barely absorbs water

Too much is usually more dangerous than too little, because rotting roots recover poorly. Dryness shows up faster, and the tree often recovers if you act quickly. You'll find more on yellow leaves in the Bonsai Doctor.

By species

• Jade plant: Stores water in its thick leaves. Let the soil dry out well between waterings. Too much moisture is its biggest risk.
• Ficus: Water thoroughly as soon as the soil is slightly dry. It forgives small mistakes quite well.
• Outdoor trees such as maple, elm or juniper: In summer they need a lot of water. Juniper likes to get a little drier in between, maple prefers evenly moist soil.

Three myths

• "A little every day." Small sips only wet the surface. Water less often, but thoroughly, when the soil needs it.
• "Ice cubes are enough." We advise against it. The meltwater doesn't moisten the root ball evenly, and many indoor bonsai come from warm regions and don't like cold roots.
• "Misting is watering." No. Misting briefly raises humidity and cleans dust off the leaves. The roots get practically nothing.

A look at Japan

Japanese gardeners have a saying: "Mizuyari san-nen" (水やり三年), "watering takes three years". It means that it takes experience before you truly have a feel for watering. That's a comforting thought: if it doesn't go perfectly at first, that's normal. For more basics, see our bonsai care overview.