It doesn't really matter to the hellebore if you prune off only the yellow leaves or all the green leaves as well. Just be sure to remove leaves with black spots or dark edges to prevent disease. The new foliage will emerge in the spring right after or sometimes at the same time as the blooms. Pruning is more to show off the flowers than it is to make the plant happy. Pruning in the dead of winter is an easy way to make sure you are removing last year's foliage and not snipping into the new growth. Another tip is to add a layer of fresh mulch right after you clip all the leaves. Hellebores love mushroom compost because it makes your acid soil more neutral. The good news is that even if you don't prune and don't mulch, your hellebores should thrive as long as they are in a cool, shaded spot with lots or organic matter in well-loosened soil. Keep growing, Marianne Binetti