Vole doormats
penstemon (Sat, 08 Nov 2014 12:15:43 PST)

It is also effective in attracting digging canines.

Requires highly-evolved canines, with no interest in digging. Border
collies, for instance.
I had one, though, who loathed the idea of rodents running around his
garden, and dispatched them with efficiency.
"Plantskydd", made from the same stuff, is odorless, though.

Bob