Herb up to 200cm, with flowers arranged in small off-white spherical flower heads.
Scientific name: Conyza sumatrensis (Retz.) E. Walker
Common names: tall fleabane, broad-leaved fleabane, fleabane
Family: Asteraceae (Compositae)
Risk Assessment score: (in development)
Synonymy: Conyza albida Sprengel, Conyza albida Willd. Ex. Spreng.
Last update: 09/07/2014
How to recognise it
Flowering: June to August.
The several Conyza species in Portugal are very similar and hard to distinguish. Additionally, the Conyza species hybridize very rapidly among themselves, originating hybrids with intermediate characteristics, causing further difficulty in the identification.
Conyza sumatrensis is distinguished from the Conyza bonariensis (hairy fleabane) by having a larger plant type (C. sumatrensis up to 200 cm; C. bonariensis up to 60 cm) and smaller open capitula (C. sumatrensis 4-8 mm; C. bonariensis 8-15 mm).
It may be distinguished from Conyza canadensis (Canadian fleabane) for having involucral bracts and densely hairy leaves (while C. canadensis has no hairs on the involucral bracts and the leaves have cilia only on the margin and on the midrib) and absence of well visible ligules.
Close-up of capitula: comparison of the three most common Conyza species in Portugal
Characteristics that aid invasion
It propagates by seed, producing a high amount of seeds that are efficiently dispersed by the wind, rapidly enhancing their distribution area.
Native distribution area
Distribution in Portugal
Mainland Portugal (all provinces), Madeira archipelago (Madeira island).
Geographic areas where there are records of Conyza sumatrensis
Europe (Spain, France, Romania, Yugoslavia, United Kingdom).
Probably accidental, very ancient.
Preferential invasion environments
A ruderal weed species, very frequent in disturbed areas: urban areas, roadsides and croplands or common lands. It also appears in natural and semi-natural areas (e.g., dunes) normally associated to disturbance events.
Impacts on ecossystems
It forms dense areas that prevent the growth of native vegetation.
High costs in applying control methodologies, mainly in crop areas.
It reduces productivity in crop fields.
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 Conyza sumatrensis include:
Physical control (preferencial methodology)
Hand pulling: it is applied to plants of all sizes. In more compacted substrates, hand pulling should be made during the rainy as to facilitate the removal of the root system.
Agricultural practices of soil mobilization (tilling, harrowing): it is applied to plants of all sizes when dense infestations occur. It should be done before flowering.
Foliar application of herbicide. Spray with herbicide (active substance: glyphosate) limiting as much as possible its application to the target species. The herbicide application should be done during the early stages of the plant’s development, before the primary axis is developed.
Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.
Alves P, Aguiar C (2012) Três neófitos novos para a Flora de Portugal. Silva Lusitana 20 (1-2): 136-138.
Carvalho JA (2008) Conyza sumatrensis (Retz.) E. Walker 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. 478-480.
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.