With its decorative, finely feathery foliage cosmos is an excellent choise for border and temporary hedges, equally at home in grand flower gardens and modest vegetable plots. Cosmos' image as peasants' flower may come from the fact, that in its early garden history in Europe it thrived best on the poorly fertilized soils of peasant gardens. In very fertile soils, the growth is lush at the expence of flowering. It's also a good cut flower if picked when just open. I usually grow a few plants just for the foliage and use it as filler in large bouquets.
Cosmos produce a lot of seed worth collecting for next year's flower garden.