I think each one will be alittle different.I've divided most of my perrenials from time to time.The basic idea is after a time the center dies out leaving the edges to live on. Dig up the plant in question and split in half or in quarters, and replant.Iris and lillies are different.Lillies are bulbs if they have spread just dig the bulbs up. some lillies spread more than others.Iris have rhizones(s?)which can be dug up and pull them apart and replanted.I'm sure someone else will comment.I'm not sure of the root system of clematis and prime rose..

The clematis should be left alone, as they shouldn't be divided. You could always try taking some cuttings from the mother plant and see how well they root for you. Personally, I've only ever had success with cuttings actually rooting from the alpina varieties. The rest of the perennials on your list should be easily enough divided providing they are large enough.

Lucky you to be able to go back and get some of your perennials after the house is sold. Most people aren't as accommodating as that.

Laurie

For dividing hostas, click on the link below...the only thing in this tutorial that I personally wouldn't do is cut off the bottom of the root ball as shown. If you are transplanting a large section or entire plant, use masking tape to tape up the leaves together. Your hosta will go through less shock with less wilt if you assist it in this way. The masking tape can just stay on until it falls off.

Some people don't even dig up the whole plant, they use a big butcher knife down through the crown and roots and take it out that way.

Caution: Disinfect tools between hostas. There is a virus that affects hostas only (HVX) that can be spread from one hosta to another through the sap in the plant. Use a 10% bleach solution or I've heard Clorox wipes works well on the smaller tools like knives pruners.

If you have more questions on hostas, please feel free to browse the GW Hosta Forum...they love "newbies" and their questions.

http://mbreiding.us/2005/hosta_div/

Here is a link that might be useful: How to divide a hosta