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Cosmos are showy annual flowers which are relatively easy to grow, as well as drought tolerant. The flowering plants are native to Mexico, and prefer warm, sunny growing spots in USDA zones three though 10. When planted in an area they like, cosmos will flourish, sometimes growing to immense heights. Their bright color and easy care make them an excellent choice for a lively summer garden. Cosmos are also insect resistant, and the plants are rarely infested by slugs, beetles, and other unwanted garden visitors.
The plants are in the family Asteraceae, the asters, along with daisies and many other boldly colored flowering plants. Two species within the cosmos genus are widely cultivated: Cosmos sulphureus and C. bipinnatus. Another cultivar, C. atrosanguineus, is more rare but has beautiful dark flowers which can look quite striking. All cosmos prefer an area in the garden which is as sunny as possible, with fertile well drained soil and minimal watering.
All cosmos cultivars have disc shaped flowers, and can grow up to six feet (two meters) if they are planted in the right spot. Cosmos sulphureus has long, narrow leaves and yellow, orange, or red flowers. C. Bipinnatus has feathery, almost fernlike foliage and flowers which are either white or pink to dark purple. C. Atrosanguineus is also known as chocolate cosmos for its stunning chocolate colored flowers. The plants are fast growing, and will produce blooms within a few weeks of planting.
Many gardeners grow cosmos from seed, covering the seeds in a light layer of soil and watering them well until they germinate. Cosmos can also be planted in seedling form, and many garden supply stores sell cosmos plants in flats for gardeners to transplant. As the plants start to grow, they should be thinned out so that the plants have room to thrive. Once the flowers start to droop and wilt, they can be trimmed off to stimulate the cosmos plant into generating more blooms. In warm regions, cosmos will bloom in May through November, before dying off in the cooler winter weather.
At the end of the season, seeds can be collected to be grown in the following year. The seeds should be stored in a cool dry place until they are ready for use. In addition to being well suited to large beds, cosmos are also good choices for container gardening, and they can be used in decorative borders along walkways or next to homes.