We have planted our Oak trees (mostly Q. robur) 18 feet apart in rows 18 feet wide. The trees are staggered in a triangular pattern. We chose that pattern as we are raising T. melanosporum and wanted to avoid to have the canopy close too early.
The only drawback with 18 feet rows is that they can’t be cut in one pass, making the maintenance a little more labor intensive as it could be with a smaller spacing.
My understanding is that most of you have chosen a denser pattern. How is it working for you? What made you decide on that pattern?