This is a wonderful summer annual that attracts butterflies and other pollinators. Seeded in spring when the soil warms up, cosmos will bloom until frost.
These are really great plants for filling in a large area on a low budget because they’re best planted from seed in the spring or even as late as now. They will grow tall very quickly. Plant them like you would wildflowers: add the seed to some sand and broadcast with a hand spreader for a naturalistic look. Rake the top of the soil to press those seeds in lightly.
They’ll come back from seed easily every year or you can collect the seeds to dry and plant where you want them next spring.
Keep the soil uniformly moist while those seeds are germinating. The seeds have very few roots when they first come out and they’re not able to take much water. Also be careful though not to drown those seeds or wash them away with too much water pressure. A gentle water breaker on the end of your hose works best. The mature height and width depends on the cultivar that you choose. Dwarf species are available and they also come in so many colors that I couldn’t possibly list them all.