I started this ponst back in June and never published it....a quick lesson on how to divide up hostas, or any perennial for that matter.
There are a few different ways you can create new plants. Planting seeds is an obvious one, as is propagating from cuttings or layering branches. Another easy way to increase your plant numbers is by dividing your plants. When we bought the new hostas for the shade tropical garden we did some dividing before we planted them. Diving plants can seem a little brutal at first, but really is easy.
When you are picking out a plant you want to divide, you want to try and get a really full, healthy looking plant that is able to be propagated through division. Some plants can be divided and other don't really like this rough treatment..
Once you get your plant home, you will need to take it out of the pot and examine the structure of the plant. You need to decide how many time you want to divide it and where you are going to make your cuts. The goal is to end up with leaves and roots in each division, so you need to do a little pre-planning. Lots of times you can see natural places to divide where the different "tuffs" of foliage come out of the ground.
Once you decide where the dividing line is going to be, it is time to cut the plant. You can use a sharp shovel of some type of a knife.
Now you will have two plants. If you want to divide them further, go ahead. I can remember and have helped my parents divide hostas down to almost one leaf. I didn't go this extreme, and divided each of the hostas into about 3-4 plants.