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![Image of Cosmos atrosanguineus Chocamocha ['Thomocha']](https://www.smgrowers.com/imagedb/Cosmos_atrosanguineusChocamocha.jpg )
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| Category: Perennial |
| Family: Asteraceae (Sunflowers) |
| Origin: Mexico (North America) |
| Flower Color: Maroon |
| Bloomtime: Summer/Fall |
| Synonyms: [Bidens atrosanguinea] |
| Height: 1-2 feet |
| Width: <1 foot |
| Exposure: Full Sun |
| Irrigation (H2O Info): Medium Water Needs |
| Winter Hardiness: 25-30° F |
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Cosmos atrosanguineus 'Thomocha' (Chocamocha Chocolate Cosmos) - An interesting clumping tuberous perennial to 12 to 18 inches tall by as wide with basal medium green colored leaves pinnately divided into broadly lanceolate leaflets that are often lobed. In late spring through fall appear the inch and a half wide dahlia like flowers with 6 to 10 (usually 8) ray deep maroon red colored petals and a central cluster of yellow orange disk flowers. The flowers, which smell faintly like chocolate in the late afternoon, rise up on a branching inflorescence that has smaller simple leaves with each flower at the top of a foot long reddish stem. Plant in full sun in moderately fertile well-drained soils and intolerant of heavy wet soils. Water regularly to get established and then occasionally through summer months. It is hardy to around 30 degrees F and useful as a perennial in USDA zones 10 to 11 but can be lifted and the tubers stored in cooler climates. This plant is an interesting and attractive border or container plant that attracts bees and butterflies and the flowers on long stems are great in bouquets. The species, Cosmos atrosanguineus, is found in mixed pine and oak forest at elevations between 5,900 and 8,000 ft in the Mexican states of Guanajuato, Hidalgo, Querétaro and San Luis Potosí. The name for the genus come from the Greek word 'Kosmos' meaning "beautiful" or "orderliness" such as "an ornament" or a "beautiful plant". The specific epithet means "dark blood red" in reference to the flower color. The history of the cultivation of the chocolate cosmos is well documented in an article by Graham Rice titled "The Story of Cosmos atrosanguineus" in the June 2017 issue of The Plantsman. Rice notes that Cosmos atrosanguineus arrived in England from Mexico, one year after first being collected in 1860 near Zimapan in Hidalgo, Mexico by by Benedict Roezl. It was described as Cosmos diversifolius var. atrosanguineus in 1861 by William Hooker and reached William Thompson, the founder of the famous Thompson & Morgan Seed Company, that same year. By 1885 Thompson & Morgan was listing seed of it and within a few years there were several named varieties being offered in the British horticultural trades but only the one called 'King of the Black' remained in cultivation and it too could not be found after 1942, likely as a result of World War II. Not only had the plant become rare in cultivation after this but there were also reports that it had become extinct in the wild, with the only remaining clone left in being a self sterile plant that had been kept alive at the Royal Botanic Gardens at Kew. The idea that it was extinct in the wild was later dispelled by research conducted by Mexican botanist botanist Aarón Rodríguez of the Universidad de Guadalajara, who in 2007 documented numerous recent records of the plant being found in the wild, commenting that populations were quite numerous. In addition there were other clones still in cultivation that were found growing in New Zealand in the 1990s and with this new germplasm further breeding of this plant has been conducted. This cultivar introduced by Thompson & Morgan Seed Compnay in 2006, is one result of this more recent breeding work. Though most (including us) list this plant as a variety of Cosmos atrosanguineus, this cultivar, Thompson & Morgan claim it to actually be a hybrid between Cosmos atrosanguineus and another unspecified species and it is noted as being particularly compact with the stems not requring staking.
This information about Cosmos atrosanguineus Chocamocha ['Thomocha'] displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.
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