I have 3 hardy hibiscus plants that are about 4 years old. Each year in early Spring, I prune them way back (about 4-6" high) - this was instructed to me - and they always grow back in gangbusters. However, each year, I notice this huge "clump" of roots/stems left behind, and most of the new growth grows from UNDER this clump, therefore causing them to grow outwards. Are there any suggestions? What should I have been doing with this clump of stems? Can it be divided? If so, how? Is it too late for this year? Can this clump be transplanted somehow?