''Cosmos atrosanguineus'', the chocolate cosmos, is a species of ''

Cosmos The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

'', native to

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It has often been claimed that it is extinct in the wild; however it is "quite abundant" in Mexico. The species was introduced into cultivation in 1885, when the British seed company Thompson & Morgan first listed it in their seed catalogue. Its dark red to brownish red flowers have a scent resembling chocolate, which is one reason for its popularity as a cultivated plant.

Description

''Cosmos atrosanguineus'' is a

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

perennial plant A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

growing to 40–60 cm tall, with a fleshy

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

ous root. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are 7–15 cm long,

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and in ...

, with leaflets 2–5 cm long. The

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s are produced in a

capitulum capitulum (plural capitula) may refer to: *the Latin word for chapter ** an index or list of chapters at the head of a gospel manuscript ** a short reading in the Liturgy of the Hours *** derived from which, it is the Latin for the assembly known ...

3–4.5 cm diameter, dark red to maroon-dark brown, with a ring of six to ten (usually eight) broad

ray florets The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

and a center of

disc floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

s; they have a light

vanillin Vanillin is an organic compound with the molecular formula . It is a phenolic aldehyde. Its functional groups include aldehyde, hydroxyl, and ether. It is the primary component of the extract of the vanilla bean. Synthetic vanillin is now used ...

fragrance (like many

chocolate Chocolate is a food made from roasted and ground cacao seed kernels that is available as a liquid, solid, or paste, either on its own or as a flavoring agent in other foods. Cacao has been consumed in some form since at least the Olmec civ ...

s), which becomes more noticeable towards the end of the day.

Taxonomy

The species was first described in 1861 by William Hooker, as ''Cosmos diversifolia'' var. ''atrosanguineus''.

Eduard Ortgies Karl Eduard Ortgies (19 February 1829 Bremen – 6 December 1916 Kilchberg, Zürich), was a German horticulturist and nurseryman. His father was a noted plant enthusiast and owned an extensive garden, so that Eduard was encouraged to choose the sa ...

later elevated it to a full species, placing it in the genus ''

Bidens ''Bidens'' is a genus of flowering plants in the aster family, Asteraceae.''Bidens''.
Flo ...

''. Andreas Voss transferred it back to ''Cosmos'', retaining its status as an independent species. It is one of eight species of ''Cosmos'' placed in section ''Discopoda''. ''Cosmos'' belongs to subtribe Coreopsidinae. In 2008, Oku, T.; Takahashi, H.; Yagi, F.; et al. analyzed the Chocolate Cosmos flower using PSID (plastid subtype identity) sequences in order to clarify the phylogenetic relationships of this plant. They determined that this species did indeed have closer relations to ''Cosmos'' than to the genus of ''Bidens'' or ''Dahlia.''

Distribution and habitat

Although it had been reported that ''Cosmos atrosanguineus'' was extinct in the wild, a research project on the genus ''

'' begun in 2007 by Mexican botanist Aarón Rodríguez found modern records starting from 1986. Field work showed that it grew in the states of

Guanajuato Guanajuato (), officially the Free and Sovereign State of Guanajuato ( es, Estado Libre y Soberano de Guanajuato), is one of the 32 states that make up the Federal Entities of Mexico. It is divided into 46 municipalities and its capital city i ...

Querétaro Querétaro (), officially the Free and Sovereign State of Querétaro ( es, Estado Libre y Soberano de Querétaro, links=no; Otomi language, Otomi: ''Hyodi Ndämxei''), is one of the Political divisions of Mexico, 32 federal entities of Mexico. I ...

and

San Luis Potosí San Luis Potosí (), officially the Free and Sovereign State of San Luis Potosí ( es, Estado Libre y Soberano de San Luis Potosí), is one of the 32 states which compose the Federal Entities of Mexico. It is divided in 58 municipalities and i ...

. It is found in mixed pine and oak forest, at elevations of around .

Cultivation and uses

Both seed-raised and vegetatively propagated

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

s are available, varying in the size, colour and shape of the petals. An article in 2017 listed 17 cultivars and seed-raised strains. , ''C.'' ''atrosanguineus'' 'Hamcoec' (trade description ) has the largest flower heads, up to 5 cm in diameter. The variation in flower color from red to black of ''Cosmos atrosanguineus'' and its cultivars results from variation in the amounts of

anthocyanin Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical compo ...

s and

chalcone Chalcone is the organic compound C6H5C(O)CH=CHC6H5. It is an α,β-unsaturated ketone. A variety of important biological compounds are known collectively as chalcones or chalconoids. Chemical properties Chalcones have two absorption maxima a ...

present.Amamiya, K., & Iwashina, T. (2016)
"Qualitative and Quantitative Analysis of Flower Pigments in Chocolate Cosmos, Cosmos atrosanguineus, and its Hybrids"
''Natural Product Communications'', 11(1), 77–78. Hybrids with other ''Cosmos'' species are also known in cultivation. As with ''Cosmos'' 'Thomocha' (), hybrids may be less scented than the species. It requires partial sun or full sun, and flowers from mid to late summer. It is frost-sensitive (Zones 6–11); in temperate zones, the tuber has to be dug up and stored in a frost-free store over the winter.

References

7. Oku, T. ; Takahashi, H. ; Yagi, F.; Nakamura, I. ; Mii, M. (2008).
Hybridisation between chocolate cosmos and yellow cosmos confirmed by phylogenetic analysis using plastid subtype identity (PSID) sequences"
''JOURNAL OF HORTICULTURAL SCIENCE & BIOTECHNOLOGY, 83 (3), 323-327'' {{commons category, Cosmos atrosanguineus atrosanguineus Flora of Mexico Garden plants of North America