Culture
Grow in average, moderately fertile, medium moisture, well-drained soils in full sun. Tolerates dryish soils. Not winter hardy to the St. Louis area where tubers should be lifted in fall (as with dahlias) and stored indoors over winter.
Noteworthy Characteristics
Cosmos atrosanguineus, commonly called chocolate cosmos, is a tuberous-rooted, tender perennial that features brownish-red flowers (to 1.5") with a chocolate scent atop slender 2-3' stems from early summer to fall. Compound, dark green leaves are pinnately divided into ovate to lance-shaped segments. Also commonly called black cosmos.
Genus name comes from the Greek word kosmos meaning beautiful.
Specific epithet means dark blood-red.
Problems
No serious insect or disease problems. Rootstocks may rot in wet soils. Not winter hardy to St. Louis.
Uses
Borders. Cutting gardens.