Unlike annuals which need to be planted each year, these flowers continue to grow even when dormant. Well-dug soil to 18 or more inches insures loose soil for roots to expand. Increasing soil fertility with compost or good organic material will benefit their growth and performance. Fertilizing newly emerging plants in early spring and again following spring and summer's flowering is beneficial. Drainage is essential.
Most perennials prefer well-drained soil.
If the soil drains poorly, this should be corrected before planting to prevent rots and disease. A garden sketch or more detailed plan is recommended only because differing heights, colors, and textures can be enhanced with some thoughtful placement. This is not critical to your success in growing perennials. If one finds the plant arrangement is unsatisfactory it is quite simple to dig and move the offender during its dormancy. Perennial flowers offer a lifetime of discovery and pleasure.