PERENNIALS FOR DIFFERENT PURPOSES : Page 603

The majority of perennials will continue to increase from year toyear and will require "dividing" and transplanting every two or threeyears. There are other perennials which should be treated as biennialsand accordingly replaced completely by new plants at the end of everysecond year. These plants, such as the foxglove, white pink, Englishdaisy, and bellflower will "run out" after a period of two or three years.They will still continue to grow, but their vigour will be so much lessthat their presence will be but an apology for strong, healthy speci-mens. All of these plants are known as perennials; but in realitythey develop only as biennials. Other perennials, such as the aster,phlox, and iris, which grow into large clumps, should be divided atleast every three years. If they are not so treated they will becomecrowded and the plants will not have space to develop properly andthe result will be spindly, unhealthy plants which will not producenormal flower effects. But the peony, in good soil, with space of adiameter of approximately three feet in which to grow, is best left togrow undisturbed for a score of years or more (Page 88).