Small annual herb, up to 80 cm, with discrete yellow and white flowers, that looks like a marigold, but with less “petals”.
Scientific name: Galinsoga parviflora Cav.
Common name: gallant soldier
Family: Asteraceae (Compositae)
Status in Portugal: invasive species (listed in the annex I of Decreto-Lei n° 565/99, of 21 December)
Risk Assessment score: (in development)
Synonymy: Galinsoga parviflora Cav. var. semicalva Gray, Galinsoga semicalva (Gray) St. John & White, Galinsoga semicalva (Gray) St. John & White var. percalva Blake
Last update: 11/07/2014
How to recognise it
Annual herb up to 80 cm, ramified, with a fragile look.
Flowers: arranged in sub-globular capitula (4-7 mm in diameter); small tri-split bracts between the flowers; small ligulate flowers (± 1 mm), almost as long as wide, generally just 5 (rarely 6), white, tri-split, tubular yellow disk flowers.
Fruits: cypselas of 1-1,5 mm long, tetragonal, provided with short hairs whose disposition is similar to a star.
Flowering: March to July.
Galinsoga quadriradiata Ruiz & Pavon is relatively similar, but it has hairs in the lower part of the stems, peduncles with many glandular hairs longer than 0,5 mm and the bracts that are found between the flower are entire.
Characteristics that aid invasion
The scarious fruits are probably adapted to dispersion along riverine lands, facilitating their expansion.
It propagates by seed producing many seeds, which are dispersed by wind, germinating easily when they find some humidity.
Native distribution area
Distribution in Portugal
Mainland Portugal (all provinces).
Other places where the species is invasive
Australia, New Zealand, North America (USA).
Probably accidental, through the Figueira da Foz port or the Coimbra Botanical Garden.
Preferential invasion environments
Crop areas and ruderal places, being very frequent in areas with some humidity, like irrigated crops and ditches. It also appears in natural and semi-natural areas.
Potentially, it reduces productivity in crop fields.
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 Galinsoga parviflora include:
Hand pulling (preferencial methodology): applied to plants of all sizes. Because it is a frequent species on humid substrates, hand pulling is usually easy; however, over more compacted substrates, hand pulling should be made during the rainy to facilitate the removal of the root system.
Soil Solarisation. It’s an alternative to hand pulling, mainly in extensive areas that are invaded by the species. It should be guaranteed that no native species are affected.
Foliar application of herbicide. Spray with herbicide (active principle: glyphosate, dicamba, etc.) limiting the exposure to the target species. The used herbicide depends on the crop species that is affected.
Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.
CABI (2012) Galinsoga parviflora. In: Invasive Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 10/11/2012].
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.
USDA, NRCS. (2012) The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA. Available: http://plants.usda.gov [Retrieved 10/11/2012].
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