Erect herb, up to 1 m, frail looking, with tiny white-greenish flowers.
Scientific name: Aster squamatus (Spreng.) Hieron.
Common name: annual saltmarsh aster
Family: Asteraceae (Compositae)
Risk Assessment score: (in development)
Synonymy: Symphyotrichum subulatum (Michx.) G. L. Nesom var. squamatum (Spreng.) S. D. Sundb.
Last update: 09/07/2014
Flowers: arranged in tiny capitula (7-9 x 2-3 mm), distributed along the lateral branches resembling a not very dense panicle; involucral bracts in several series, green with a violet and scarious margin; ligulate marginal flowers, greenish-white; tubular centre flowers, greenish.
Flowering: May to November.
Characteristics that aid invasion
It propagates by seed, producing many seeds, of which are efficiently dispersed by wind.
It has a strong invasive behaviour, able to expand and colonize new habitats in a short period of time.
Native distribution area
Central and South America.
Distribution in Portugal
Mainland Portugal (all provinces), Azores archipelago (islands of São Miguel, Santa Maria, Terceira, Graciosa, São Jorge, Pico, Faial, Flores), Madeira archipelago (islands of Madeira and Porto Santo).
Geographic areas where there are records of Aster squamatus
Europe (Spain, Greece, Italy, France), Northern Africa (Algeria, Egypt, South Africa), Australia.
Preferential invasion environments
It presents great ecological resilience, adapting to different conditions as long as soil humidity is assured.
Environments that are subject to human intervention (wet crops, roadsides, abandoned gardens, ruins, harbours, rice fields, heaps, etc) and semi-natural (halophyte communities, marshlands, degraded streams, etc).
It prefers soft climates along the sea surface or over lowlands, or else in sheltered environments.
Impacts on ecossystems
It forms monospecific mats, preventing the development of native vegetation.
Potentially high costs in applying control methodologies in crop areas.
Due to the high production of pollen, it is considered an allergenic plant.
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 Aster squamatus include:
Physical control (preferencial methodology)
Hand pulling: to be applied to plants of every size. It is convenient to perform the action before fructification. On more compact substrates, hand pulling should be made during the rainy season as to facilitate the removal of the root system.
Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.
Carvalho JA, Silva L, Land EO (2008) Symphyotrichum subulatum (Michx.) G. L. Nesom var. squamatum (Spreng.) S. D. Sundb. In: Silva L, Land EO, Luengo JLR (eds) Flora e fauna terrestre invasora na Macaronésia. Top 100 nos Açores. Madeira e Canárias, Arena, Ponta Delgada, pp. 315-317.
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.