Another trident maple

Published on 3 April 2024 at 09:14
Trident maple bonsai planted on a lava rock

This is an imported Trident maple (A. buergerianum) that is grown with its roots over a lava rock. Trident maples are often used for this style of bonsai, because their roots grow very fast and strong. When properly attached to a rock, they can grow around it in a couple of years. In my previous blog post you can read about a ROR maple that I'm growing from seed.

This tree hasn't been repotted since it was imported, so it was very pot bound and in need of root pruning and repotting.


repotting a trident maple bonsai
The roots mass of this tree is very dense. It hasn't been repotted for a number of years.

The root mass was so dense that water couldn't properly flow through. The old soil had completely broken down and what's left is just a mass of roots and hard clay. If you leave a bonsai in a pot in this state for too long, it will wither!

Combing out the roots of this maple bonsai.
Roots of a trident maple bonsai

When you repot (deciduous) bonsai, always start by removing the top layer of old soil. That way, you uncover the surface roots (Nebari in Japanese) first and know exactly how deep in the pot the roots are. You can then cut away excess roots from the bottom of the root ball. If you do it the other way round, you might risk cutting away too of the root ball.

Work your way around the root base with a wooden chopstick, starting at the trunk and going outward. After removing the top part of the soil, you can go round the edges and the bottom of the root ball.

In the pictures above, you can see long roots that have grown following the round shape of the pot. These will be cut to (sort of) an equal length. Some things to keep in mind:

  • Prune back thick roots harder than thin roots. This 'distributes' energy around all the roots.
  • Remove roots that are growing down and up.
  • Remove or untangle roots that are crossing each other.


After pruning the roots, the root ball is compact and ready for repotting

With decidous trees, and especially maples, you can easily remove 50% of the roots. Just try to leave as much feeder roots as possible. After removing the old soil and pruning the roots, you should end up with something like this.

The bonsai in its old pot.
The soil mix I use consists of akadama and pumice.

The tree was then secured in its old pot using aluminum wire. I added a 50/50 mix of akadama and pumice and made sure the soil mix was worked in between the root mass.

After repotting, don't fertilize for about 6 weeks in order to protect the new roots!

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