On Sep 29, 3:25*pm, "CraigT" wrote:
I'm putting in a 2 course retaining wall around some shrubs in raised beds
in the front yard where previously there were *landscape timbers. *Since I
was only going up 2 courses (8") I just figured to dig down a couple of
inches and lay down some sand to make leveling easier. *But, then I was
thinking that maybe pea gravel or crushed limestone would be better or maybe
I should go deeper. *What do you guys think? *By-the-way this is in zone 5
(Michigan).

Are you talking about the interlocking concrete retaining wall block?
If so, you don't need gravel or crushed limestone under such a minimal
'retaining' wall. It's really more of planting bed edging. Even if
the ground freezes up, the whole thing, planting bed and all, will
rise and fall with the drop in temperature below freezing. There's
not enough of a structure to be disturbed by such an ebb and flow.
Fear not.

R