Scientific name: Arctotheca calendula (L.) Levyns
Family: Asteraceae (Compositae)
Risk Assessment score: (in development)
Synonymy: Arctotis calendula L., Cryptostemma calendulaceum (L.) R. Br.
Last update: 09/07/2014
How to recognise it
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.
Flowering: June to August.
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
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
Europe (Spain, Italy), Australia, New Zealand, western USA (California), Asia (Japan), South America (Chile).
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.
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:
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.
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.
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.