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Cosmos sulphureus Cav.

Protologue
Icon. 1: 56, t. 79 (1791).
Family
Asteraceae (Compositae)
Chromosome number
2n = 24
Synonyms
Bidens sulphurea (Cav.) Sch.Bip. (1856).
Vernacular names
Orange cosmos, yellow cosmos, sulphur cosmos (En). Cosmos soufré (Fr). Cosmos amarelo (Po).
Origin and geographic distribution
Cosmos sulphureus originates from Central America (Mexico) and northern South America, where it is still found in the wild. It has been introduced as an ornamental in many countries all over the world, in tropical Africa e.g. in Senegal, Cameroon, Sudan, Tanzania, Malawi, Zambia, Zimbabwe, Mozambique, Réunion and Mauritius. Sometimes it has escaped from cultivation and behaves like a weed, e.g. in Tanzania, Malawi, Zimbabwe, the United States and Canada.
Uses
The flower heads of Cosmos sulphureus and other Cosmos, Bidens and Coreopsis species have been major sources of yellow to orange dyes among the precolumbian civilizations of Central and South America. In southern Africa, they were adopted as a popular yellow dye by European settlers for domestic textile production and are still used by dyers using natural dyes as a hobby or for textile crafts, to dye wool bright yellow or orange. The flowers should first be boiled for about one hour before adding the mordanted wool to the cooled dye-bath and resuming boiling. Pre-mordanting the fibres with different metallic salts gives various shades of lemon yellow to burnt orange. As a top-dye after a first red dyewood bath (e.g. of Baphia nitida Lodd.), it helps give a scarlet bloom to wool while on indigo-dyed wool, it produces greenish-brown shades. Cosmos sulphureus is commonly cultivated as an ornamental.
Properties
The flower heads of most Cosmos, Bidens, and Coreopsis species contain flavonoid dyes of the chalcone and aurone groups. The specific flavonoids in Cosmos have not been fully elucidated, though the following have been found: luteolin, a group of flavonols having quercetin as their aglycone, and a group of chalcone glycosides. These are all good yellow colorants. The traditional medicinal applications in China of Cosmos and Bidens species have been confirmed by the fact that Cosmos and Bidens extracts are shown to inhibit bacteria, fungi, and viruses and to have potent anti-inflammatory effects in laboratory animal experiments with induced gastric ulcer, liver inflammation, or arthritis-type swelling.
Botany
Annual herb up to 1.2(–2) m tall, with 4-angled, branched, pubescent to glabrescent stem. Leaves opposite, sessile or with clasping petiole up to 2 cm long; blade ovate in outline, up to 7 cm × 5 cm, very deeply dissected with ultimate segments narrowly oblong, c. 2.5 mm wide, apiculate, glabrous. Inflorescence a head c. 1.5 cm in diameter, solitary and terminal on stem and branches; peduncle up to 22 cm long (often much less); outer involucral bracts narrowly ovate, c. 12 mm long, acuminate, inner bracts with membranous margin. Ray flowers c. 10, corolla oblong-obovate, up to 3 cm long, apex 3-toothed, deep orange; disk flowers with narrowly funnel-shaped corolla, 5-lobed, c. 7 mm long, orange-yellow, subtended by scales c. 9 mm long. Fruit an achene c. 2 cm long, blackish, with a scabrid beak c. 7 mm long; pappus of 2 horizontally spreading awns c. 5 mm long.
Cosmos comprises about 25 species from tropical America; it belongs to the tribe Heliantheae and is related to the much larger genera Bidens and Coreopsis. Cosmos sulphureus as an ornamental comprises several cultivars.
Ecology
Where Cosmos sulphureus has been found in the wild in Africa, it is a common roadside weed which does not spread into undisturbed localities. In southern Africa it flowers and fruits in March–May.
Management
Cosmos sulphureus is propagated by seed. The flower heads of about two dozen plants are sufficient to dye 0.5 kg of wool or silk. They should be harvested when they open. They are soaked in water and the mixture is cooked until the flower heads become pale. The dye bath is yellowish in an acid solution (e.g. with vinegar) and reddish in a basic solution (e.g. with ammonia or washing soda). Alum and tartaric acid are often added as a mordant. The textile is simmered in the dye bath until the desired depth of colour is achieved, usually after about one hour.
Genetic resources and breeding
Cosmos sulphureus is widespread in Central America and elsewhere it may behave as a weed. It does not seem to be in danger of genetic erosion. Breeding efforts are directed towards development of large-flowered ornamentals.
Prospects
As a source of orange to yellow dyes, Cosmos sulphureus will remain only locally of importance in southern Africa and in Western countries.
Major references
• Hind, D.J.N., Jeffrey, C. & Scott, A.J., 1993. Composées. In: Bosser, J., Guého, J. & Jeffrey, C. (Editors). Flore des Mascareignes. Famille 109. The Sugar Industry Research Institute, Mauritius, l’Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM), Paris, France & Royal Botanic Gardens, Kew, Richmond, United Kingdom. 261 pp.
• Matlack, P., 2002. Growing dye plants. Growing weld, madder, woad, and cosmos in the garden and how to extract and use the natural dye pigments on wool and silk. [Internet] http://tntn.essortment.com/grow ngdyeplan_rgia.htm. Accessed August 2004.
• van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
• Wild, H., 1967. The Compositae of the flora Zambesiaca area, 1. Kirkia 6(1): 1–62.
Other references
• Berhaut, J., 1974. Flore illustrée du Sénégal. Dicotylédones. Volume 2. Balanophoracées à Composées. Gouvernement du Sénégal, Ministère du Développement Rural et de l’Hydraulique, Direction des Eaux et Forêts, Dakar, Senegal. 695 pp.
• Borghetti, F., 1998. Effects of the maternal photoperiodic conditions of maturation on the fresh matter and germination of akenes of Bidens sulphurea Sch. Bip. Ciencia e Cultura Sao Paulo 50(5): 385–390.
• Cardon, D., 2003. Le monde des teintures naturelles. Belin, Paris, France. 586 pp.
• Dharmananda, S.A., undated. Bidens: a popular remedy escapes notice of western practitioners. [Internet] http://www.itmonline.org/arts/bidens.htm. Accessed January 2005.
Author(s)
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
D. Cardon
CNRS, CIHAM-UMR 5648, 18, quai Claude-Bernard, 69365 Lyon, Cedex 07, France
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Jansen, P.C.M., 2005. Cosmos sulphureus Cav. In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.