If you have hostas that are going to get very large, put smaller ferns away from under the eventual spread of the plant. (experience, I now have to move several ferns that are being covered up). Ferns that hold their own with the hostas in my garden are maidenhair, chain fern, sensitive fern and ostrich fern (but beware, the last two are aggressive spreaders). Small to medium hostas exist well with Japanese painted fern,lady fern, ghost fern, woodsia, holly fern. and others that get only 1-2' tall. Otherwise, all the ferns in my garden exist happily with the hostas, same conditions, water, light, etc.