|What exactly is "dividing"? What plants/flowers need it? Why do they need it? How do you do it?
|Division is a way to make one plant into many. It consists of separating the plant to make numerous small ones from one "mother", usually by cutting the rootball into sections. Each new division would have roots and a portion of the crown for top growth. The new plants are essentially identical to each other and to the original plant in that they are literally pieces of the mother plant.
Many perennials can be divided and that is often the preferred method of propagation by home gardeners. Divisions may be larger (such as multiple crowns and six inches across) or very small (such as one crown) depending on the gardener's goal.
Some commonly divided plants would include garden phlox, shasta daisies, Siberian iris, daylilies, rudbeckia, echinacea, dianthus, achillea, perennial geraniums, and so on.
In addition to dividing a plant to propagate it, a plant may also be divided in order to rejuvenate it or possibly to control its spread. Many perennials benefit from being divided every few years.