I love to buy high quality Japanese Maples and turn them into bonsai. The problem is they come in large pots – typically 3 gallon. That’s a lot of roots! Way too many roots for a bonsai pot. After much trial and error, I realized that I could slowly (I mean slowly) reduce the roots each month in a series of raking’s and soakings. I like this method because I don’t have to wait for the plant to go dormant to do root pruning and then hope I didn’t do too much root pruning. Because If I do too much root pruning while the tree is dormant, It will die, but slowly as it comes back to life.
In the photo below, you can see how I have been taking soil out slowly.
Here is the root ball after the tree has been pulled from the pot. As you can see, the root ball is too large for a bonsai pot and I have gotten to the point where it is all roots.
Here, I am taking a rake and lightly dragging it across the outer surface of the root ball. I’m keeping the pressure light so I don’t do a lot of damage, but since the root ball is down to the roots, I know I am doing some. But here is the inspiration that made me realize this would work: Bugs and critters eat the roots from time to time and do moderate amounts of damage, yet the tree recovers. If I simulate this small damage and give the tree time to recuperate, then not only am I expediting the time it takes to get the tree into a bonsai pot, I am helping the tree strengthen itself.
Here is a photo of the root ball in process.
Here is the finished root ball. In all, I probably took off about a ¼ of an inch. The outer roots were damaged, but it will actually stimulate new growth. This is why I have found I need to alternate raking with soaking on alternate months.
Below is the tree and root ball back in the pot. You can see how there is a little more space in the pot. Next month, I will take my garden hose to the root ball and let the water wash away some dirt. This way, the roots will have 2 months to heal back before I rake them again.
This process will actually keep the roots the same size because they grow back at the rate I am removing them, but the soil will be dislodged from the roots and the root ball will be more compact. When the tree goes dormant, then, I can cut 15-20% of the roots back as normal. Then, the roots will fit into a bonsai pot, and I won’t have to be too aggressive with the root pruning.
After you do this, you will have to keep your plant in the shade, and keep it well watered. If you remember nothing else, remember this: