How to Grow a Chocolate Cosmos Flower

Plant chocolate cosmos tubers in rich, well-draining soil.

Chocolate cosmos (Cosmos atrosanguineus) reaches heights of 30 inches and produces an abundance of daisylike blooms. Colors range from a brown-red to a dark-burgundy making this cosmos a striking addition to perennial beds. Color isn't its only notable feature. Chocolate cosmos emits the rich fragrance of chocolate, making it suitable for sensory or fragrance gardens. Unlike other cosmos, chocolate cosmos is a tender perennial hardy in U.S. Department of Agriculture plant hardiness zones 8A and 10A. In cooler climates, lifting and storing the tubers for the winter keep this plant producing for years.

Things You'll Need

• Garden tiller
• Organic matter, compost or manure
• Garden spade
• Box or crate
• Peat moss

Instructions

1. Select a location that receives full sun for six to eight hours a day. Although chocolate cosmos survives in less light, full sun enhances blooming.

2. Till the soil to a depth of 8 to 12 inches. Spread a 2- to 4-inch layer of organic matter, such as compost or well-rotted manure, over the area and till it into the soil. Organic matter improves drainage and aeration, while releasing nutrients into the soil, as it breaks down. Cosmos prefer organic-rich, well-draining soil.

3. Plant chocolate cosmos in the spring once the danger of frost has passed in your area. Position the tubers in the soil to a depth of two to three times the tuber’s diameter. This allows adequate room for root growth and provides support for the growing plant. Cover the tubers with soil and firm down lightly with your hands securing the roots.

4. Watering thoroughly moistens the soil to the tubers’ depth. Keep the soil evenly moist until shoots emerge. Reduce watering to once or twice a week, or whenever the soil feels dry 1 inch below the surface.

5. Deadhead old blooms as soon as they begin fading. This improves the plant’s appearance while encouraging blossom production. Chocolate cosmos blooms from the early summer until fall when provided adequate water and regularly deadheaded.

6. Dig up chocolate cosmos tubers, unless you live in zones 8A to 10A, once frost kills the foliage in the fall. Cut any remaining foliage back and store the tubers in a box or crate filled with moist peat moss. Place it in a cool, dark place for the winter. Replant the tubers in the spring.

Tips & Warnings

• Plant chocolate cosmos near the deck or seating areas of your yard.

• Fragrance from chocolate cosmos is strongest at the end of a warm day.

• Do not to overwater cosmos. The soil should be moist, but should not soggy.

References

• Washington State University Extension; Chocolate Cosmos; Cheryl Greenwood Kinsey
• Washington State University Clark County Extension; Chocolate Plants

Resources

• University of California; Indulge in a Chocolate Garden; Dorothy M. Downing
• The United States National Arboretum; USDA Plant Hardiness Zone Map; Henry M. Cathey; January 1990