| Hi Suzzy, Don't do any dividing now, it's done in the Spring when you take them out to plant. My method is to bend the rizomes and they will tell me where they want to divide. I break them off there. This is also the time to take off any weak or rotted or otherwise unhealthy looking growth and discard. If your clumps are too big to store easily use the above method to find where the clump is weakest and separate them there, but don't do too much separating just enough to manage them. Wounds as the plant goes dormant will not be healthy for regrowth in the Spring. Hope this helps! | 
