Cosmos caudatus
(wild cosmos)

Preferred Common Name

• wild cosmos

Other Scientific Names

• Bidens artemisiifilia ssp. caudata (Kunth) Kuntze
• Bidens berteroana Spreng.
• Bidens carnea Heer
• Bidens caudata (Kunth) Sch.Bip.
• Cosmea caudata Spreng.
• Cosmos caudatus var. exaristatus Sherff

Local Common Names

• Cuba: romerillo
• Dominican Republic: yema de huervo
• Germany: Cosmee; Schmuckblume
• Indonesia: kenikir
• Malaysia: ulam raja
• Puerto Rico: clavellillo; margarita; piquete
• Russian Federation: kosmos chvostaty

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Asterales
•                         Family: Asteraceae
•                             Genus: Cosmos
•                                 Species: Cosmos caudatus

Asteraceae is one of the largest families of flowering plants with about 1620 genera and more than 23,600 species (Stevens 2012). Vegetatively the members of this family are extremely variable, but they are readily recognized by their flowers (florets) in heads (capitula) surrounded by an involucre of bracts. The small, single-seeded fruit (cypsela), often has a plumose pappus, that aid in wind dispersal (Stevens 2012), but not so in Cosmos, which belongs to a group of genera that have awns instead of fthe eathery pappus. 

Cosmos spp. were originally distributed in the tropical and subtropical regions of the New World, especially North America. About 40 species are currently recognized, with the centre of diversity in Mexico. Several species have been introduced around the world and have become naturalized, and occasionally invasive. They are closely allied to the ‘beggars tick’ genera Coreopsis and Bidens and whose generic boundaries are currently in a state of flux.

Cosmos caudatus has cryptogenic origins in southern Mexico, Central America or the Antilles. A review by Melchert (1990) suggests that it is native to the gulf slopes of Mexico from Tamaulipas through Veracruz and the Yucatan Peninsula and perhaps further afield. It was first collected by von Humboldt and Bonpland, near Havana, Cuba in 1801. The type of Bidens berteroana is from Puerto Rico, collected by Bertero in 1818 (Sprengel, 1826). It is confusing that this species was described with yellow flowers (Kunth, 1818) although the current species concept has flowers pink to purple (Sherff, 1932, 1955, 1964; Melchert, 1990). For his circumscription, Kunth may have had only dried herbarium material with bleached flowers.

Melchert (1990) identified that the then concept of C. caudatus included a self-compatible tetraploid (C. caudatussens. Sherff) and a self-incompatible diploid, which he described as C. pacificus (C. caudatus var. exaristatus Sherff) with two varieties. Strother (1999) returned the second variety, C. pacifica var. chiapensis, to C. caudatus, however, there is no mention of the status of C. pacifica var. pacifica. Strother’s concept would then have C. caudatus with diploid and tetraploid populations. On the other hand, Kiger (2006) has kept Melchert’s concept as the tetraploid only (2n=48) and it is only the self-compatible tetraploid that has been reported as invasive.

The Malaysian common name ulam raja means "the King's salad”, referring to the edible nature of the plant.

Annual herb 0.3–2.5 m high, with a weak taproot. Stems erect, branched, glabrous or sparsely hispid. Leaves cauline, alternate, deeply lobed; petioles 10–70 mm long; blades 100–200 mm long; ultimate lobes 2–10 mm wide; margins spinulose-ciliate; apices acute, often mucronulate. Synflorescences 100–300 mm long, spreading with linear-subulate bractlets 6–10 mm long; apices acuminate. Capitula 5–15 mm diam.; involucral bracts erect, oblong-lanceolate, 7–11 mm long with apices acute to obtuse apices; ray florets rose-pink to purple; laminae oblong-oblanceolate, 5–15 mm long with obtusely 3-lobed apices; disc florets 5–6 mm long. Cypselae light brown, 12–35 mm long, glabrous or scabridulous proximally, setose distally; pappus 2–3 widely divergent to reflexed awns 3–5 mm long (description compiled from Pruski 1997; Beentje and Hind 2005; Kiger 2006; Puttock pers. obs.). 

C. caudatus was brought by the Spanish from Mexico to southeast Asia, via the Philippines. It was present in Cuba in 1801 and Puerto Rico in 1818, as verified by the types of the two early names for this taxon. In Fiji it was reported as a weed “common everywhere, sometimes in pure stands on waste land in both islands up to 500 feet” (Greenwood 1943).

This species will spread in disturbed areas and also invade undisturbed areas to a lesser extent. It is commonly found around old settlements and weedy agricultural land, and open forest. It is classified as being an agricultural and environmental weed, commonly escaping cultivation and becoming naturalized. It is classified as an invasive weed in Florida, Puerto Rico and the Dominican Republic. 

Soil drainage

• free

Soil reaction

• neutral

Soil texture

• light
• medium

Special soil tolerances

• shallow

C. caudatus spreads by seeds carried by animals and dropped locally. 

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Has high genetic variability

• Reduced native biodiversity

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately

C. caudatus was brought by the Spaniards from Mexico to Southeast Asia via the Philippines. The plant is edible and widely used as a Malay herbal salad vegetable. It is also regarded in Malaysia as having medicinal value. It contains high mineral content and possesses high antioxidant activity which may be beneficial in bone disorders such as postmenopausal osteoporosis. It is also traditionally used to promote blood circulation.

C. caudatus has economic importance as a horticultural plant, with numerous cultivars.