Lily is a 13 week cocker.

How can we get her to 'drop' what she has in her mouth?!?

She picks up so much stuff to chew - leaves, grass, soil, wood, bark etc (don't think she swallows it), but if we try to get whatever it is she's picked up off her, she doesn't like it -- will growl, run away etc, and other than getting our fingers in there, won't give it up!! She's not even interested in exchanging what's in her mouth for food or toy!!

Any suggestions/ideas will be greatly apperciated!!