Planted in every combination imaginable, the vast array of varieties of perennial flowers are brief visitors to the summer flower garden, but highly desired by gardeners nonetheless. They die down to their roots in autumn and regrow in spring. Many varieties live for years, increasing their size and flower production each year. Because of their longevity, they require ideal soil and cultivating practices to keep them healthy and robust enough to withstand winter's cold temperatures.
With few exceptions, perennials grown for their flowers require six or more hours of full sun per day in order to grow and bloom successfully in the perennial border. If you have a choice between morning and afternoon sun, choose morning sun; it is much less harsh than the hotter afternoon sun, which can stress your plants and cause the flowers to fade rapidly.
Fertile, Well-Drained Soil
Perennial flowering plants will increase in size and produce more blooms each year, providing the soil in which they grow is rich, fertile, well-drained and full of organic matter. Add as much compost as you can to your flower beds and at least a 1-inch layer of peat moss to the surface of the bed before planting it. Dig these amendments into the soil with a garden shovel. Apply a mulch of half-finished compost after planting your perennials; it will retard the growth of weeds, feed the plants and enrich the soil as it decomposes.
Access to Water
Most perennial flowers require some form of irrigation to flourish. If possible, install a simple irrigation system buried in the soil before planting your perennial border. Many systems are available commercially that hook up to your garden hose and require no special plumbing. Another option is to thread a soaker hose among the plants in early spring before they grow too large. Covered with mulch, the hose can stay in place all season. Simply screw its leading end into your garden hose when it's time to water.