This Red Maple (Acer rubrum) was collected at the edge of a field in spring 2019. Two years later the pot is filled with roots and I can start developping the nebari.

Acer rubrum repot
Red maple in spring 2021
Acer rubrum repot
Compact root ball after 2 years

I removed any root growing towards the center, the bottom or crossing other roots. A large section is cut under the trunk to flatten the root mass and promote a radial distribution.

Acer rubrum repot
Roots after clean-up
Acer rubrum repot
The remainder of the tap root was cut

The tree was then planted in a hand-made wooden box with a few inches of extra room for growth. I use a substrate made with equal parts of chabasai, haydite and perlite.

Acer rubrum repot
Wooden box
Acer rubrum repot
Repotting completed

Next steps

I will let the tree grow freely all summer long, with the exception of some trimming of top growth to let the bottom sections thrive. Next year I will try to graft branches along the lower section of the trunk. This will enable me to air layer the two top sections (along the red lines) to build a more compact tree. All the branches will be grown from the bare trunk.

Acer rubrum repot
Air layers locations
Acer rubrum repot
Future trunk line