Cosmos caudatus
(wild cosmos)

Pictures

Identity

Preferred Scientific Name

• Cosmos caudatus Kunth

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

Summary of Invasiveness

C. caudatus is a prolific seed-producing annual that grow to 2.5 metres tall sporting very attractive heads of flowers. There are many cultivars of C. caudatus and some of these have become popular in the horticultural trade, especially in the Philippines and Malaysia. The seeds are viable in the appropriate climatic zones and are hitchhikers on clothing and animal fur.

C. caudatus is included in the Global Compendium of Weeds (Randall, 2012). It is troublesome and difficult to control in the tropics. C. caudatus spreads by seed. This species will spread in disturbed areas and also invade undisturbed areas to a lesser extent.

Taxonomic Tree

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

Notes on Taxonomy and Nomenclature

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.

Description

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.). 

Plant Type

Distribution

There is no clear consensus of the origins of C. caudatus, however, it is generally assumed as native to southern Mexico, and appearing weedy wherever it occurs in Central America and the Antilles. It was present in Cuba and Puerto Rico by 1801 and 1818 respectively (Kunth 1820; Sprengel 1826). Melchert (1976) described C. caudatus in Guatemala as “a tropical weed occurring in damp roadside thickets, wet tropical grasslands, cultivated fields, etc.” and Robinson (2006) in Ecuador as widely cultivated and naturalized. Although D’Arcy (1975) described the species as native to Central America and the Antilles, he implies that all four species of Cosmos in Panama are introduced. It is also listed as introduced in Ecuador (Jørgensen and León-Yánez 1999).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

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. 

Introductions

Risk of Introduction

The risk of introduction of Cosmos caudatus is relatively high. This species is broadly dispersed by humans and has the potential to grow as a weed in ruderal areas, and agricultural and pasture lands. C. caudatus has been reported as a roadside and ruderal weed in Central and South America, Australia and southeast Asia. Consequently, this species has the potential to spread much further than it has to date.

Habitat

C. caudatus occurs naturally in grassy slopes and banks and in monsoonal deciduous forests. It is a common weed in disturbed areas, pastures, and roadsides throughout central American and the Caribbean. In South America it is found on roadsides and in remnant dry forest and semideciduous secondary forest from 30 to 900 metres altitude (Robinson 2006). It occurs in similar habitats wherever it has become established in the Old World tropics.

In Fiji, it is found "occurring from sea level to about 200 m, sometimes cultivated but frequently naturalized as a weed in waste places and along roadsides” (Smith, 1991). In Queensland, it is found from near sea level to 800 m, and usually grows around old settlements or as a weed of agricultural land. Also found in open forest and sometimes in vine thickets and monsoon forest (Centre for Australian National Biodiversity Research, 2010).

Habitat List

Biology and Ecology

Genetics

C. caudatus is a self-compatible tetraploid with a chromosome number of 4n = 48 (Melchert 1968, 1990; Robinson et al., 1981). The report of 2n = 12 for a specimen from Michoacan, Mexico, by Keil et al. 1988 is likely to be of C. pacificus (= C. caudatus var. exaristatusSherff 1964).

Reproductive Biology

Flowers in C. caudatus are pollinated by hymenoptera (bees) and lepidoptera (butterflies). Arnold et al. (2014) report that the species is adapted for pollination by both honey bees and megachile bees, and that the narrow tubular flowers also makes them ideally adapted for butterflies. Species of butterflies and bees visiting the flowers when grown in Madhya Pradesh, India, are listed by Arnold et al. (2014).

Longevity and Phenology

C. caudatus is an annual herb and under favourable environmental conditions produces flowers and seeds in spring and summer months.           

Environmental Requirements

C. caudatus grows as a garden escape, roadside and ruderal weed. It needs full sunlight and moderate water availability to grow.  

Climate

Latitude/Altitude Ranges

Soil Tolerances

Soil drainage

• free

Soil reaction

• neutral

Soil texture

• light
• medium

Special soil tolerances

• shallow

Means of Movement and Dispersal

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

Pathway Causes

Pathway Vectors

Impact Summary

Risk and Impact Factors

• 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

Uses

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. 

Uses List

General

• Botanical garden/zoo

Human food and beverage

• Vegetable

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

Ornamental

• Potted plant
• Propagation material
• Seed trade

References

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Arnold R; Tiwari S; Saxena A; Mishra RM; Anand P; Pandey R, 2014. Ecological Studies of Natural Populations of Cosmos caudatus, H. With Special Reference to Pollination, Seed Behavior and Biomass Distribution. Journal of Chemical, Biological and Physical Sciences, Section B: Biological Sciences, 4(1):324-328.

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Links to Websites

Contributors

03/10/2014 Original text by:

Christopher F. Puttock, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA

Distribution Maps