We love hostas and used to grow them mostly in pots with copper strips around the pot to keep out the slugs - but last year we discovered a product called 'Strulch', which is a mineralised mulch made of wheat straw. Slugs hate it. We now have a big bank of hostas in a semi-wooded part of the garden, plus hostas in the ground in several other places, and not one iota of slug damage. An application of strulch is supposed to last for two years (we won't know if it does until next Spring). I don't know if a similar product is made in the US - here's a link to the English one:
http://www.strulch.co.uk
