How do I divide hosta plants?
Hennepin County Minnesota
Here is some good information from the U:http://www.extension.umn.edu/garden/yard-garden/flowers/dividing-perennials/
You do not have to wait until next spring to divide the hosta if it is necessary for you to do it now. However, you should probably wait until early Fall when the weather is not so hot which can contribute to transplant shock.
Lift the entire hosta clump with a shovel. Wash the soil from the roots so it easier to see where to cut to divide the clump. Cut with a sharp shovel or knife to make the divisions. In smaller plants, it may be possible to gently pull apart the plants, leaving as much of the root attached to each crown or plant. Space these division at their mature size. Keep newly divided plants well watered for the first two weeks.