Anything perennial is something that happens over and over on a regular basis. Perennial plants are those that take a rest period every year, then continue to grow when conditions are amenable. A perennial plant should be chosen carefully and planted into the landscape with its mature size in mind. Some perennials stay small whereas others, like trees, grow to take up considerable space. Perennials bloom and set seed, but always save some energy to keep them alive through rest periods. Bulbs, corms, tubers and rhizomes are perennials just like shrubs and trees. Plan the living foundation of your garden with perennials, starting with the largest (like trees) and working down to the smallest (groundcovers and miniatures). While you wait for your perennial to grow, you can fill in vacant spaces with annuals or biennials.  Often perennials will grow better with mild feeding as they can deplete soils where they live over a period of time.