1. Baccharis halimifolia L. (U.S.A., Mexico, West Indies) – A rare but increasing, locally naturalised escape from cultivation. The invasion history of Baccharis halimifolia in Belgium is well-documented by Rappé & al. (2004). It was introduced on purpose in coastal dunes in the first half of the 20th century (for instance in Raversijde in 1924), probably as a windbreak. First recorded as an (ephemeral) escape in the port of Oostende in 1948 (Lambinon 1957). In the past decades much planted as an ornamental in public green in coastal areas and increasingly seen as an escape in numerous, widely scattered localities along the Belgian coast since 1997 (mostly centered between Adinkerke and Oostduinkerke, around Blankenberge and between Zeebrugge and Knokke). Exceptionally seen in inland localities and then mostly ephemeral or as a mere relic of cultivation. In 2012, however, about six old bushes were discovered near an abandoned sand pit in Mol, obviously well-established since quite a long time (see: http://waarnemingen.be/waarneming/view/72111211).
Baccharis halimifolia produces large amounts of viable seed that is easily wind-dispersed. It is now frequently seen selfsown in a wide range of habitats, artificial as well as natural: cracks in pavement, quays and walls, sea dunes, beaches, saltmarshes,… It is very salt tolerant and relatively frost resistant. Baccharis halimifolia has been able to naturalise in worthy, vulnerable native habitats, for instance in the nature reserve “Baai van Heist” since 1999. In view of its invasive behaviour in southwestern Europe it is now monitored and eradicated in such habitats. Additional information on its invasiveness in Belgium and elsewhere in western Europe is available at: http://ias.biodiversity.be/species/show/41 and http://www.q-bank.eu/Plants/Factsheets/Baccharis%20halimifolia%20NL.pdf. See also Fried & al. (2016).
 |
 |
 |
 |
Selected literature:
Bavoux C., Burneleau G., Corneille M. & Mimaud L. (2010) Statut du séneçon en arbre Baccharis halimifolia (L.) (Dicotyledones, Asteraceae) à l’île d’Oléron (Charente-Maritime). Ann. Soc. Sci. Nat. Charente-Maritime 10(1): 16-22.
Campos J.A., Caño L. & Herrera M. (2014) La invasión de Baccharis halimifolia en la costa cantábrica. Ambienta 109: 78-91. [available online at: https://www.researchgate.net/publication/270574240_La_invasin_de_Baccharis_halimifolia_en_la_costa_cantbrica]
Caño L., Campos J.A., García-Magro D. & Herrera M. (2013) Replacement of estuarine communities by an exotic shrub: distribution and invasion history of Baccharis halimifolia in Europe. Biol. Invasions 15: 1183-1188. [available online at: https://www.researchgate.net/publication/260203160_Invasiveness_and_impact_of_the_non-native_shrub_Baccharis_halimifolia_in_sea_rush_marshes_fine-scale_stress_heterogeneity_matters]
Fried G., Cañob L., Brunel S., Beteta E., Charpentier A., Herrera M., Starfinger U. & Dane Panetta F. (2016) Monographs on Invasive Plants in Europe: Baccharis halimifolia L. Botany Letters, DOI: 10.1080/23818107.2016.1168315. [available online at: http://www.tandfonline.com/doi/pdf/10.1080/23818107.2016.1168315]
Lambinon J. (1957) Contribution à l’étude de la flore adventice de Belgique. I. adventices rares ou nouvelles pour la Belgique. Bull. Soc. Roy. Bot. Belg. 89: 85-100.
Rappé G. (2006) Baccharis halimifolia. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 176.
Rappé G., Verloove F., Van Landuyt W. & Vercruysse W. (2004) Baccharis halimifolia (Asteraceae) aan de Belgische kust. Dumortiera 82: 18-26.
Van Valkenburg J., Duistermaat L. & Meerman H. (2014) Baccharis halimifolia L. in Nederland: waar blijft Struikaster? Gorteria 37: 25-30.
Van Valkenburg J.L.C.H., Meerman H., Bollen G. & Zwart A. (2017) Baccharis halimifolia L. in de herkansing. Gorteria 39: 1-4. [available online at: http://www.repository.naturalis.nl/document/646592]
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.