Experiments are slow in bonsai. I still have a lot of questions and a lot to learn about what I am calling ‘Ground Boxes.’ You can read my first post on this topic HERE. For those who want the short version, I planted several trees into wooden frames with mesh bottoms (as pictured below) directly on the ground to test a hybrid approach between growing in a container and planting in the ground to thicken trunks.
That was two years ago and I thought it was time to see what things are looking like by lifting one of the Amur maples. Amur maples aren’t particularly fast growers, but this plant had grown to over five feet (over 1.5 meters) and the trunk was thickening accordingly. I expected some roots to grow through the mesh at the bottom, so I started by cutting under the box with the flattest shovel I had.
With only two years of growth, I had no problem cutting through roots that held the box tightly to the ground, but I did encounter my first problem will cutting it loose. The wooden frame was falling apart at the corners where the moisture had rotted the lumber. It was pressure treated lumber, to resist such rot, but it was also reclaimed from an old section of fence where it had served outside for years prior. Newer wood may last longer than two years, and older boxes will likely hold together just fine until you start lifting them with a shovel, but this is a consideration for the approach.
Once lifted I needed to scrape soil away from the wire mesh and cut roots that were coming through.
As expected, none of the roots that grew through the mesh were particularly large.
I pulled the rotted box apart and raked the roots. Then I took the opportunity to do a heavy root pruning to promote an improving root structure as it continues to grow. I also removed 4 feet from the height of the plant to encourage the growth on the lower part of the trunk.
I decided to extend this experiment into a variation on the original box design. I cut most of the bottom out of a plastic tray, lined the bottom with the same wire mesh, and set this tree up to continue growing in this ground box 2.0.
This box will be settled against the ground, as before, and the tree allowed to grow freely again.
I will follow this process with one or two other trees this spring. It may be informative to lift one of the more vigorous trident maples to see the difference.
Regardless, I think I have a functional hybrid approach. The trees are growing far faster than they would in a pot, cutting roots to lift the box from the ground seems easier than digging a tree that was planted directly, and the box contains the majority of the root mass. The wooden box did come apart, but if I leave trees in place even longer, the loss of a wooden frame over 5 or 6 years of growth will seem well worth it.
I will continue to experiment, and update you as I learn more.
Bonsai Iterate 