“How do I water this bonsai tree?” had to be the most common question I answered when I worked in a bonsai shop. Unfortunately, that question requires some nuance, but once you’ve considered it, watering your bonsai tree will be a breeze and become second nature to you.
A Eurya bonsai via Wikimedia Commons
What is a bonsai?
Let’s start with the basics because this will help us in deciding when and how to water your bonsai tree. The way we use “bonsai” in English is as an umbrella term for any tree that is growing in a pot.
The “tree” can be any species. It can be a deciduous or an evergreen tree. Or it can be plant material that isn’t even a tree at all. The species of tree you’re growing will determine how much water your bonsai needs. A willow bonsai will require a lot more watering than a jade bonsai.
Bonsai soil and pots
Generally speaking, bonsai tree soil is fast-draining and doesn’t retain a lot of water. The size of the pot the bonsai is growing in will also affect when and how you water your tree. Smaller pots will hold significantly less soil than larger pots and may require watering 2-3 times a day.
Seasonal bonsai growth
Whether the tree is actively growing is probably the biggest factor on how much water your bonsai tree needs. Trees entering dormancy will require less water. If your tree is flowering and fruiting it will need extra watering to support those flowers and fruits.
Bonsai tree location
Lastly, the location of your bonsai tree will have a big impact on how much water it will need. For example, if your tree is sitting in full sun during the middle of summer, you will need to water multiple times per day. If your tree is sitting on your porch, under an awning, or in dappled shade from a nearby tree, it will not dry out as fast and will probably do fine being watered once every couple of days.
Photo via Goodluz
Best bonsai watering techniques
YouTube user easternleaf demonstrates the two best bonsai watering techniques on two juniper bonsai in his collection in his YouTube video on how to water a bonsai tree.
The first is top-watering and the one you’re most familiar with if you have ever watered a container garden. Top-watering requires a watering can or water hose with the attachment that creates a gentle stream of water that best mimics a rainfall. Hold your hose or watering can over your tree for 30-60 seconds so that the water saturates the soil.
The second bonsai watering technique, bottom-watering, is the easiest of the two and my preferred method of watering small, potted plants. In it you fill a small tub or container with water and gently set your bonsai tree into the water until the water level reaches the rim of the bonsai pot. You can leave your bonsai sitting in water from a few minutes up to half an hour. Don’t worry, your tree will not drown from sitting in water for a short period of time.
Both of these two watering techniques get the job done, but you may find that you prefer one over the other. Top-watering may be easier for you if you have a large tree, or if you have many trees that you need to water quickly and effectively. Whereas, bottom-watering may be best for you if you have one tree and you like to dote over it and fret over every little leaf that may fall. It is easier to under-water a bonsai tree than it is to over-water one.