tree rings what border to use?

[contourbs]

whats would be a nice border for a tree ring besides black plastic?

[LawnScapers of Dayton]

I prefer nothing but a clean cut edge through the sod.

[stoneseller]

Border Concepts make tree rings out of steel. Seem them here:

http://www.borderconcepts.com/edging_accessories.asp

[steve in Pa.]

I would use ep henry coventry curbstone's. They look great when installed!