Dividing
Perennials can be divided if they grow too large. With summer-flowering plants this should be done in October or November, and with spring-flowering plants in June. In dividing you simply dig up the plant and break off as much of it as you want, being careful not to injure the roots. As, however, there are many plants which, to be divided, must be cut, and as this is an operation which requires some skill and knowledge, it would perhaps be better to take advice.