Nebari is a Japanese word which refers to the area where the lower trunk meets the roots of the tree. Species such as maples and pines are noted for strong surface roots so a good bonsai of one of those species should also show great nebari. Here’s a way to create better nebari in your developing bonsai.I start with a small seedling and thread it through a hole in a piece of sheet metal. Some people use steel washers but I think the sheet needs to be a little bigger to get the roots to spread wide. Mine are 6-10 cm diameter. Circles would probably be better but squares were easier to cut.
Too shallow and the roots might dry out as they form. Unless you are trying to grow a formal upright tree, plant so that the trunk is at an angle – bonsai with the lower trunk emerging from the soil at an angle are far more dynamic than vertical trunks.
As the trunk thickens the metal cuts off circulation where the trunk goes through the hole. This forces the tree to produce callus and new roots just above the metal sheet so it can survive. The new roots are forced to grow horizontally over the metal plate forming a new lateral root system. With good management and a little luck you should get radial roots all around the trunk.
I keep these in the nursery for the first summer where they get watered every day. The new roots will be forming in the heat of summer and must not dry out while they are new formed and tender.
After the first growing season you should have plenty of new roots above the plate. These new roots should be cut short to promote ramification
then the tree can be planted into a grow pot or into the ground for maximum growth and trunk thickening. Eventually sap circulation to the old roots below the plate will be cut off and that part will die off.
A year or 2 later the new lateral roots system will have started to fuse together to create a large, plate like nebari.
Now it is time to start developing show stopping branches on your new trident trunk.
This method is also great for producing small, shohin sized maple bonsai.