Once planted, Cosmos flowers should begin to grow in the summer, and continue growing into the fall, if you take care of them. Once you see little flower buds beginning to grow, just water them regularly, careful not to make the soil to wet.
The most common species that you usually see is the Cosmos bipinnatus. They are commonly known as Garden Cosmos. They are about 2 feet tall and grow in colors of white, red, and pink.
The bipinnatus comes in different kinds such as Candy Stripes, Daydream, Seashells, and Sonata.
Sonatas are dwarfs that have blossoms that are multicolored. Candy Stripes are white blooms with an outer edging in the petals that is crimson red.
Daydream flowers are predominately white, with a pink center. Seashells come in pinks and white. They may start out in one color and then have a different shade at the tips of their petals.
If you live in an area with hot summer sun, you may want to plant Cosmos sulfurous. They adapt better then Garden cosmos to the hot sun.
They bloom flowers in yellows and oranges. Some types of this variety also bloom doubled petals.
The variety you choose will have to be a choice of what type of colors or color scheme you are working on for your garden. Also think about the weather in your region before planting a specific species.