Cosmos is another great annual for the beginning gardener. Depending on the variety, it ranges in height from 12 inches to 36 inches or more. It loves hot weather, and grows well in mediocre soil. It's one of those rare plants that doesn't perform as well if you give it too much attention. Mixing different types in your garden will not only give you a blend of sizes and colors, but will also provide you with beautiful cut flowers.
Cosmos is easy to grow from seed and will germinate in less than two weeks. It can be started indoors six weeks before the last frost, or put directly into the ground. Plant it about ¼ inch deep in a sunny location, and water lightly. You can also purchase established plants in most garden centers. Set them into the ground at the same level as the dirt enclosure in which they came, and space about 15 inches apart. Water very lightly. Be very careful not to over water cosmos. Unless the summer is very dry, once a month watering may be all that is necessary. The taller varieties may need to be staked.