Cosmos flowers are an essential for many summer gardens, reaching varying heights in many colors, adding frilly texture to the flower bed. Growing cosmos is simple and cosmos flower care is easy as well as rewarding when single or double blooms appear on stems reaching 1 to 4 feet. Planting cosmos flowers results in many uses of the specimen, such as cut flowers for the indoor display and backgrounds for other plants. When planting cosmos flowers, locate them in soil that has not been heavily amended. Hot dry conditions, along with poor to average soil, are optimum conditions for growing cosmos.