Hi Denys, > I was thinking to crush the pumice stones I kept > when our outdoor b-b-q went bust, and spreading > the ground material around my hostas.? Don't breathe the dust. Get the stones wet first and wear a mask. There may be fat from cooking in the stones. This might attract badgers, skunks, foxes, dogs and cats which might dig up your hostas. I don't think it would harm your plants. Leo Martin Phoenix Arizona USA