Boyce, I use a product named PermaTill OneTime to help break up clay soils. The product claims that is it can be used to line a planting hole, it will protect from voles. YMMV good luck. Randy.R zone7b >deer and fritillaries >Boyce Tankersley (Tue, 13 Mar 2012 13:50:21 PDT) > >Voles seem to enjoy the non-stinky Fritillarias bulbs in the Chicago area, >much to our disappointment. > >Boyce Tankersley >Chicago Botanic Garden >