Although plants are often safer from slugs and snails if they're in containers, try to avoid using pots that have lipped rims. These rims make good hiding places for the pests, notes Val Bourne, an organic and wildlife gardening expert. Use straight-sided pots instead, she advises.
It is also possible to choose varieties of hostas that are less susceptible to slug attacks, due to their thicker leaves. Examples include 'Devon Green' and 'Firn Line' hostas, available from Breck's.
Even if you manage to avoid an onslaught of slugs and snails, hostas planted in pots can suffer from another pest: vine weevil grubs, which eat the plants' roots. 'Tap the plant from its pot and look for small  white grubs with brown heads,' says John Negus, a gardening expert. If you find the grubs, he suggests either washing all the soil off the roots and repotting it in fresh compost, or killing the pests with a nematode.