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Galinsoga parviflora

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 Decreto-Lei nº 92/2019, 10 july)

Risk Assessment score: 20 | 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: Galinsoga parviflora Cav. var. semicalva Gray, Galinsoga semicalva (Gray) St. John & White, Galinsoga semicalva (Gray) St. John & White var. percalva Blake

Last update: 11/07/2021

Family: 
Asteraceae (Compositae)
Appearence: 
Grasses and herbs

How to recognise it

Annual herb up to 80 cm, ramified, with a fragile look.

Leaves: up to 5 cm, ovate, acute to acuminate, serrate.

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.

 

Similar species

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

South America.

 

Distribution in Portugal

Mainland Portugal (all provinces).

 

Geographic areas where there are records of Galinsoga parviflora

Other places where the species is invasive

Australia, New Zealand, North America (USA).

 

Introduction reasons

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.

Economic impacts

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:

 

Physical control

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.

 

Chemical control

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">Invasive species">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].