To the owner of the new chair:
 
Chicken wire, baby.  It's cheap, you can get it at Home Depot (at least
that's where I got mine), It tacks on easily with thumbtacks (or large
head roofing nails), and it will keep out the most determined of ferts.
 
Otherwise, take the legs off.  Those are the only two sure-fire options I
know of, less than actually boxing in the bottoms with paneling or plywood
(scrap paneling is pretty cheap).
 
Just my $0.02,
Stephanie
 
and Angus, Honey, and Baby Bela.
Missing MissKitty....
[Posted in FML issue 3254]