Instead of a brick/rock, I cut a piece of wire and shape it as a "U" and pin the rhizome into place. I have a variety of wildlife that tramples through my garden all day...every day. That wire helps hold them in place when they get stepped on, kicked, or partially dug up. You don't have to worry about forgetting the wire, it usually rots away in a year (in wet conditions). In our very dry times here, I did find and remove several wires from last season.
