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Arctotheca calendula

Annual creeping herb, with flowers similar to a daisy, yellow on the margins and black in the centre.

Scientific name: Arctotheca calendula (L.) Levyns

Common names: capeweed, South African capeweed

Family: Asteraceae (Compositae)

Status in Portugal: invasive species (listed in the Decreto-Lei nº 92/2019, 10 july)

Risk Assessment score: 28  | Value obtained according to a protocol adapted from the Australian Weed Risk Assessment (Pheloung et al. 1999), by Morais et al. (2017), according to which values above 13 mean that the species has risk of having invasive behavior in the Portuguese territory | Updated on 30/09/2017.

Synonymy: Arctotis calendula L., Cryptostemma calendulaceum (L.) R. Br.

Last update: 09/07/2021

Family: 
Asteraceae (Compositae)
Appearence: 
Grasses and herbs

How to recognise it

Annual creeping herb, rising up to 40 cm on the extremities.

Leaves: from 7-20 cm, pinnatisect, rough-puberulent on the upper surface and tomentose-white on the lower surface.

Flowers: arranged in capitula of 3-5 cm diameter; external involucral bracts with scarious margins, frequently with a terminal appendix with deep indentations; ligulate flowers on the margin of the capitulum of 15-20 cm, yellow on the upper surface, purple on the lower surface; flowers with a blackened-green centre.

Fruits: densely woody cypselas, making the capitulum (in frutification) appears very dense.

Flowering: June to August.

 

Similar species

There are many species of daisies that have some resemblance, but the colour (blackened-green) of the capitulum’s centre and the lower surface of the leaves (tomentose-white) are distinctive characteristics.

 

Characteristics that aid invasion

Species of rapid growth with creeping stems that may reach 2 m long.

It propagates vegetatively through stem fragments. These fragments, as long as they have a node, root easily originating a new plant.

It also propagates by seed; the seeds are dispersed by animals, wind and water, being able to originate dispersion foci in distant locations.

Native distribution area

South Africa.

 

Distribution in Portugal

Mainland Portugal (Minho, Trás-os-Montes, Douro Litoral, Beira Litoral, Estremadura, Ribatejo, Alto Alentejo, Baixo Alentejo, Algarve).

 

Geographic areas where there are records of Arctotheca calendula

Other places where the species is invasive

Europe (Spain, Italy), Australia, New Zealand, western USA (California), Asia (Japan), South America (Chile).

 

Introduction reasons

Probably accidental.

 

Preferential invasion environments

Arid, sandy locations, including disturbed, cultivation and gardened areas. It also invades natural and semi-natural areas, appearing frequently on coastal dunes.

Impacts on ecossystems

The rapid vegetative growth leads to the formation of impenetrable mats that may inhibit the development of native vegetation.

 

Other impacts

Allergies.

It is considered toxic to mammals, due to the accumulation of toxic levels of nitrates.

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.

The control methodologies used for Arctotheca calendula include:

 

Physical control

Hand pulling (preferencial methodology): applied to plants of all sizes. Because it is a frequent species on sandy substrates, hand pulling is usually easy; however, if in more compacted substrates, hand pulling should be made during the rainy as to facilitate the removal of the root system. It should be guaranteed that no larger roots/fragments are left in the soil.

Soil solarization. It’s an alternative to hand pulling, mainly in extensive areas that are invaded by the species native species are affected.

 

Chemical control

Foliar application of herbicide. PSpray with herbicide (active principle: glyphosate or triclopyr) limiting the exposure to the target species. The use of this method should be made with caution, once that in Australia, repeated applications of the herbicide, lead to the appearance of resistant biotopes.

 

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

Alvarez M (2000) Arctotheca calendula. In: Bossard CC, Randall JM, Hoshovsky MC invasive">Invasive Plants of California’s Wildlands. University of California Press, Berkeley, CA, pp. 182-187.

 

 

CABI (2012) Arctotheca calendula. In: invasive">Invasive species">Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 10/11/2012].

 

 

 

 

Dana ED, Sanz-Elorza M, Vivas S, Sobrino E (2005) Especies vegetales invasoras en Andalucía. Consejería de Medio Ambiente, Junta de Andalucía, Sevilla, 233pp.

 

 

 

 

Marchante E, Freitas H, Marchante H (2008) ) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.