Photo Credit: Lynne Resch of Fleurs du Bien, who grew Cosmos 'New Choco' from Farmer Bailey plugs. 

Common Name chocolate cosmos
Genus  Cosmos
Species C. Atrosanguineus
Family Asteraceae
Life Cycle  Herbaceous perennial with fleshy tuberous roots. 
Tray Size  50
Plug Care Do not allow to dry out fully, harden off and plant, or bump up soon after receiving plugs. 
Netting / Staking Not absolutely necessary, one layer of netting may help  keep stems straight in windy areas. 
Temperature Range Chocolate cosmos are heat loving plants and are only hardy in zones 9-11. 
Spacing 12"
Soil Preference Loose, well draining soil with average fertility. An excess of nutrients will cause heavy foliage growth with few flowers. The tuberous roots are at risk of rotting if the soil isn't free-draining. Neutral to slightly acid pH is best. 
Day Length Long day plants - will bloom readily from early summer through to frost. Plant in full sun.   
Pinching One or two pinches while the plants are young will  encourage vigorous side branching and more blooms  later in the season. 
When to Plant Plant in the spring after all threat of frost has passed. 
Harvesting Harvest when buds are beginning to open. Cut deep to  get the longest stem possible and to encourage the plant to send up more long stems. 
Post Harvest Care Cut stems should immediately be placed into cool water. With the use of a floral preservative expect a vase life of around a week. 
Diseases / Insects Powdery mildew can set in during long periods of damp  conditions, or at the end of the season when spores are  more prevalent in the environment. Keep the foliage dry  while irrigating and spacing the plants to allow for more air flow to help prevent this. Watch closely for aphids, which may attack this crop. 
Bailey's Notes

Chocolate cosmos are often grown for their fragrance  which is often described as a sweet chocolate/vanilla  scent. This is due to the plant producing a compound called vanillin - the same compound found in the vanilla  bean. The scent may be stronger toward the end of the day.  

Under optimal growing conditions these plants *may*  produce tubers by the end of the season that can be dug and stored over the winter, similarly to dahlia tubers. While this is true for wild-type chocolate cosmos, newer cultivars were likely bred with other characteristics in mind and may not be the strongest tuber producers.   

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