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Baccharis spicata

A dioecious perennial shrub with narrow, opposite leaves and flowers arranged in a spike-like inflorescence.

Scientific name: Baccharis spicata (Lam.) Baill.

Common name: narrow-leaved broom.

Family: Asteraceae/ Compositae

Status in Portugal: Invasive species (listed in Decree-Law no. 92/2019, 10th July).

Risk Assessment Score: [in development]

Synonymy: Eupatorium spicatum Lam., Baccharis platensis Sprengl, Baccharis attenuata Don ex Hook. & Arn.

Last update: 06/22/2020

Avistamentos actuais da espécie: 
Family: 
Asteraceae (Compositae)
Appearence: 
Trees and shrubs

How to recognize it

Dioecious shrub (male and female flowers on separate plants) up to 2.5 m, grayish-green in color.

Leaves: lower leaves opposite, upper leaves opposite to alternate, without petiole, elliptic to linear, 40-80 × 2-13 mm, acute at the apex and margin with widely spaced teeth.

Flowers: gathered in inflorescences in the form of unisexual chapters, yellow flowers (in males) and yellowish-white (in females) gathered in racemose inflorescences that resemble spikes.

Fruits: 0.7-1 mm. cypresses with white papillus, produced in large numbers on female plants.

Flowering: August to November (in Portugal; in the native area flowering is from February to April).
 

Similar species

Baccharis spicata is easily distinguished from most other species in the same family by having lower leaves that are always opposite and racemiform spike-like inflorescences.

Characteristics that aid invasion

Production of a large number of seeds easily dispersed by wind. Vegetative propagation after cutting.

Native distribution area

South of Brazil, Paraguay, Uruguay and northeast and central Argentina.

Distribution in Portugal

Continental Portugal (Douro Litoral - populations detected in Matosinhos, Vila do Conde and Póvoa de Varzim).

For more detailed locations of this species, please check the online interactive map. This map is still incomplete - we need your help! Contribute by submitting location records of the species where you know it.

Geographical areas where there are records of Baccharis spicata 

Other places where the species is invasive
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Introduction reasons

Accidental introduction, probably through the Port of Leixões.

Preferential invasion environments

In the area of origin it typically grows in steppes and grasslands, but can occur in disturbed coastal areas, abandoned fields and riverine zones. Where it has been detected in Portugal, it grows in disturbed terrain, in the company of the marsh grass (Cortaderia selloana), a species that occupies similar environments, both in Portugal and in its area of origin (Chile and Argentina).

Impacts on ecosystems

It grows vigorously and forms dense clumps that dominate shrub vegetation, using the resources available to other species.

Economic impacts

High costs in the application of control measures.

Other impacts
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Natura 2000 Network habitats more subject to impacts

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 Baccharis spicata include:

Physical control

Hand pulling: whenever possible, including root removal. Start with isolated female plants (machinery may be required depending on the size of the individuals) to reduce the ability to re-invasion and dispersal. The risk of erosion should be assessed, which may limit the areas in which this method can be applied. In the first instance, it is best suited to adult individuals up to ca. 1.5 m (resulting from germination) and occurring in low density. Plants that have been uprooted should not be left in the ground to prevent them from re-rooting - they should be removed (e.g., to furnaces/incineration plants) or stacked in the area where they were cut, but ensuring that the roots do not come into contact with the ground.

They can be cut or uprooted before flowering to prevent seed formation and dispersal. Still, after removal of adult female (seed producing) plants it is expected that many seeds will germinate, so this should be taken into consideration and continuity controls should be ensured. Shade can decrease germination

In cases of established invasions (with seed formation), the operation should be repeated over several years to deplete the seed bank in the soil.

Chemical control

Cutting followed by application of herbicide on the clump: Must be applied within seconds. Active ingredient: glyphosate at ca. 50% of the commercial product; triclopyr can also be used. Up to ca. 25% of the clumps can be expected to burst, so several follow-up checks are necessary. This application is recommended in the fall. This method has relatively good effectiveness, especially on stressed specimens (e.g., if they occur in very dry areas, ...) but it must be ensured that the cut material is properly "routed", in particular to prevent existing fruit on the plants from dispersing.

Biological control
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Visit the How to Control page for additional and more detailed information on the correct application of these methodologies.

 

Verloove, F.; Dana, E.D.; Alves, P. (2017) Baccharis spicata (Asteraceae), a new potentially invasive species to Europe. Plant Biosystems, An International Journal Dealing with all Aspects of Plant Biology, DOI: 10.1080/11263504.2017.130300.