A background is a must. Use a hedge, shrub border, a trellis, a fence, or a wall. Perennials prefer full sun and well-drained soil. Choose plants that will give continuous bloom. A good arrangement is tall plants in the back, low ones. in the foreground, and medium ones in the middle with strong accent plants placed irregularly in the middle sections. Plant so as to mass varieties in groups of three to five or more. Consider foliage in this planning.