Howdy folks,
On the production side of the garden bed, run some weed cloth down
the inside of the block to prevent some of your weeds like Bermuda
grass that propagate underground from taking up residence under the
blocks or in the cavities or else you'll be fighting them forever. On
the outside of the walls holding a garden bed, run some weed cloth
flat, and cover with a heavy mulch to keep the weeds away from the
wall, and save on trimmer string.
This is more of a gardening tip than a construction tip but you do
want to do it when you build the wall so it is a consideration during
construction.

Steve Coyle
www.austingardencenter.com