Tithonia rotundifolia
(red sunflower)

Preferred Common Name

• red sunflower

Other Scientific Names

• Tagetes rotundifolia Mill.
• Tithonia aristata Oersted
• Tithonia speciosa (Hook.) Hook. ex Griseb.
• Tithonia uniflora Desf. ex J.F.Gmel.
• Urbanisol aristatus (Oerst.) Kuntze
• Urbanisol heterophyllus (Griseb.) Kuntze
• Urbanisol tagetiflora Kuntze
• Verbesina szyszylowiczii (Kuntze) Hieron

International Common Names

• English: giant Mexican sunflower; Mexican-sunflower; red marigold; shrub sunflower; tree marigold
• Spanish: chilicacate; clavel de muerto; flor amarilla; jacalate ; margarita roja; varga amarga

Local Common Names

• Brazil: girassol mexicano ; margarida-mexicana
• Haiti: belle Vénus
• Mexico: acahual; acaute de flor; tzum; zuum
• Puerto Rico: escopeta

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

The genus Tithonia comprises about 11-20 species with a centre of distribution in Mexico and Central America (Morales, 2000; Flora of North America Editorial Committee, 2018; The Plant List, 2018). Tithonia species are variable in life forms (i.e., herbs, shrubs, small trees), life span (including annuals, biennials and perennials) and their patterns of distribution ranges from widely distributed to restricted endemics (Morales, 2000). Two species, T. diversifolia and T. rotundifolia, are widely cultivated as ornamentals and have escaped to become invasive weeds in many tropical and subtropical areas around the world (Morales, 2000; Davidse et al., 2018).

Annual herb, up to 4 m tall. Stems at first densely pilosulous with short hairs, in age glabrate; leaves alternate, petiolate, the blades rather thin, ovate to triangular-ovate, mostly 7-20 cm long, acuminate, cuneate (or sometimes almost truncate) at the base and then contracted and decurrent on the petiole, simple or sometimes trilobate, the margins serrate, hispid-pilose on both surfaces, especially on the veins, scabrous, glandular-punctate beneath; heads long-pedunculate; involucres 2-3 cm broad; phyllaries biseriate, 1.5-2.5 cm long, subequal or graduate, the outer ones lance-oblong to ovate-oblong, acute or acuminate, finely pilosulous, the herbaceous apex often lax or reflexed, the inner phyllaries similar but usually shorter; ray flowers 9-13, the ligules golden yellow or orange, 2-3 cm long; disc flowers yellow, the corollas puberulent, about 9 mm long; pales acuminate to cuspidate, hispidulous above, 12-18 mm long; achenes more or less appressed-pilose or glabrous, 6-7 mm long; pappus awns 2, early deciduous, or those of the outermost flowers sometimes wanting, 3-6 mm long, the squamellae united nearly to the apex, irregularly dentate, about 2 mm long (Nash, 1976).

T. rotundifolia has been widely introduced as an ornamental across tropical and subtropical regions of the world. In South Africa, T. rotundifolia was introduced in the early 1900s as an ornamental plant, but is abundance has been escalating over the past 12 years and now it is listed as invasive in KwaZulu-Natal, Gauteng, Limpopo, and Mpumalanga provinces. Across South Africa, T. rotundifolia can be found invading protected areas, agricultural lands, urban and rural areas, areas near waterways, disturbed sites, railways and roadsides (Henderson 2007; Mawela, 2014). T. rotundifolia can also be found extensively naturalized across West and Southern Africa and is listed as invasive in Zimbabwe, Zambia, Kenya, Uganda, and Tanzania (Muoghalu and Chuba, 2005; Muoghalu, 2008; BioNET-EAFRINET, 2018).

In the West Indies, the date of introduction of T. rotundifolia is unknown, but it was collected in the wild as early as 1885 in Puerto Rico, 1871 in the Dominican Republic, 1903 in Martinique, and 1904 in Cuba (US National Herbarium).

In Belgium, T. rotundifolia was first recorded in 2015 on the banks of the Schipdonk canal in Merendree. It was described as an exceptional and ephemeral escape. Plants probably germinated from soil contaminated with wild flower seed mixtures and birdseed. T. rotundifolia seems to be an exceptional alien in Europe (Verloove, 2018).

Soil drainage

• free

Soil reaction

• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile

T. rotundifolia spreads by seeds. Mature plants produce a large number of seeds that are dispersed by wind, water, animals, and in clothing. Seeds can also be dispersed in dumped garden waste and contaminated agricultural produce. Seeds can remain dormant in the soil for up to 4 months (Upfold and Staden, 1990; Patel and Manhad, 2014; BioNET-EAFRINET, 2018; ISSA, 2018).

Intentional introduction

T. rotundifolia has been intentionally moved over large distances by humans to be used as an ornamental (BioNET-EAFRINET, 2018; USDA-ARS, 2018).

T. rotundifolia has negative impact on agricultural production. It is a weed of crop fields, orchards and citrus plantations (Villaseñor and Espinosa, 1998; Vibrans, 2009).

T. rotundifolia is an aggressive pioneer species that quickly invades open grounds, abandoned fields, forest edges, disturbed sites, riverbanks, roadsides, and disturbed secondary forests. Once established, it grows forming dense stands with negative impact on native biodiversity as they outcompete and displace native vegetation, alter natural regeneration and obstruct access to riverbanks. This species is particularly problematic across Africa, principally in South Africa where it has been declared a Category 1 invasive weed (Henderson, 2007; Mawela, 2014; ISSA, 2018) and in Zimbabwe, Zambia, Kenya, Uganda, and Tanzania where it is regarded as a noxious weed and invasive plant (Muoghalu and Chuba, 2005; Muoghalu, 2008; BioNET-EAFRINET, 2018).

In South Africa, T. rotundifolia often forms dense stands along road verges that can obstruct motorists' vision (ISSA, 2018).

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• 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
• Gregarious

• Ecosystem change/ habitat alteration
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Reduced native biodiversity
• Threat to/ loss of native species
• Transportation disruption

• Allelopathic
• Competition - monopolizing resources
• Competition - smothering
• Hybridization
• Rapid growth

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field
• Difficult/costly to control

T. rotundifolia is widely cultivated as a garden ornamental and hedge plant ((ISSA, 2018; USDA-ARS, 2018). The flowers of this species are reported to yield a good grade of honey (Nash, 1976). In East Africa it is also grown for green manure (BioNET-EAFRINET, 2018).