I few years back I read about using a CD to ground layer a tree. The method called for taking a CD, Britney Spears CD’s work best, slipping the center hole over the trunk of the tree snaking it down to the base of the roots. The CD actually needed to be a few inches below the surface. Then the hope was that once the trees trunk diameter got big enough the CD plastic would cut off the circulation of the cambium to the roots and force sugar to concentrate in the trunk area right above the CD. This would then cause roots to develop and hopefully radially emanate while the tap root and the associated roots would choke off.
I slipped a number of CD’s over my trees with many of the CD’s cracking from the force of the trunk expansion. One tree that did show some nice results was a Prunus mume with white flowers:
As one can see there are some thick roots that have developed, somewhat radially,above the CD as I was hoping. This tree is maybe 4-5 years old and has really taken off like a shot in my bonsai garden.
The CD is cracked but this is a recent thing since the last time, a few months ago, I dug down to the CD with my fingers the CD was intact.
So, then I broke off the CD plastic from the trunk, which wasn’t too hard, and then sawed off the part of the trunk below the CD. I was actually surprised to find that the trunk section below the CD still seemed alive or atleast not rotted.