Kyla, I think its all personal preference. I have some clumps that are larger than yours that I have not divided and they still bloom. Once in awhile you get a picky one that needs to be divided or it will not bloom well. I have found that to be few and far between here. As long as they are watered well and get a little fertilizer it should be fine, unless of course you would rather divided it so you can plant it in more than one location.
