I've only tried seed. I have read that if you want to divide, you need to use young plants. I can verify that the older the plant, the less success you will have digging it up to move it around, much less divide it. They develop thick tap roots which resent disturbance. This would be the only way to achieve a continuation of a particular named plant, but seed is much the easiest way to increase your stand.
Seed requires double cold stratification with warm periods at the start and in between.
The other is E. x martini , a natural hybrid who is variable and may resemble either of its parents. Both of these are still on my wish list. Gardening in Shade is just one of the of over forty different gardening topics you can visit here on Suite 101, covering everything from annuals to zucchini. If you're not a member of Suite101, become one - it's free and easy to do. Once you join, you can pop into any discussion and let me know what's on your mind.