Bulletin OEPP/EPPO Bulletin (2014) 44 (1), 5–10 ISSN 0250-8052. DOI: 10.1111/epp.12089

European and Mediterranean Plant Protection Organization Organisation Europe´enne et Me´diterrane´enne pour la Protection des Plantes

EPPO Data sheets on invasive alien plants Fiches informatives sur les plantes exotiques envahissantes

Baccharis halimifolia L. Asteraceae – Groundsel Bush

Identity Asia: Georgia, in Abkhasia, on the eastern coast of the Black Sea (Westman et al., 1975; Kikodze et al., 2010). Scientific name: Baccharis halimifolia Linnaeus EPPO Region: Belgium (Verloove, 2008), France (Thel- Synonym: Baccharis cuneifolia Moench lung, 1916; Muller, 2004), Italy (Zanetti, 1997; Arrigoni & Taxonomic position: Dicotyledons, Asteraceae Viegi, 2011), Spain (Allorge, 1941), and the UK (Clements € Common names: Gewohnlicher kreuzstrauch [DE], eastern & Foster, 1994). baccharis, groundsel baccharis, groundsel bush, seepwillow Note: the species had been recorded in the Netherlands, but [EN], tres Marıas [ES], baccharide a feuilles d’halime, is not known to be present anymore in this country (van Valk- ß senecon en arbre [FR] enburg et al., 2013). The plant is also recorded as planted in EPPO code: BACHA the Ataturk arboretum in Istambul, but has so far not been Phytosanitary categorization: EPPO A2 List recorded in the wild (Ibreliler Website, www.ibreliler.com).

Geographical distribution History of introduction and spread In Australia, the plant was first introduced for ornamental pur- Native range poses around 1900 in Queensland. By 1930 it was considered North America: Canada (Nova Scotia), Mexico (Mexico, invasive, spreading to neighboring areas, and is now recorded Nuevo Leon, San Luis Potosi, Tamaulipas, Veracruz; Flora in New South Wales (Sims-Chilton & Panetta, 2011). of North America Website), the USA (Alabama, Arkansas, The first record of B. halimifolia in the EPPO region dates Connecticut, Delaware, Florida, Georgia, Louisiana, Mary- back to 1683 in France, where it was introduced for orna- land, Massachusetts, Mississippi, New Jersey, New York, mental reasons (Fournier, 1936). There are indications of its North Carolina, Oklahoma, Pennsylvania, Rhode Island, cultivation in several botanical gardens, for instance, in Paris South Carolina, Texas, Virginia, West Virginia; Flora of in 1796 (Jardin des Plantes) or in Montpellier in 1824 (AME North America Website). & CBNMP, 2003). During the 19th century, the cultivation of Carribean: Bahamas (Correll & Correll, 1982), Cuba B. halimifolia as an ornamental plant was recommended in (Weber, 2003; USDA-ARS Website). several horticultural books (Duhamel du Monceau, 1800; Du- Note: In Canada, B. halimifolia reaches its northern limit puis & Herincq, 1884). The plant was particularly used for range and it is considered as an extremely rare Atlantic its tolerance to salinity, both in soil and in wind spray. It is coastal plains species, occurring only in Tusket River estu- also widely used as an ornamental plant on roadsides and ary and its vicinity. Official conservation programmes are roundabouts in coastal areas, and is also used on canal shores being implemented in this area (Nova Scotia Website, Spe- for stabilization, and more rarely in areas where small game cies at Risk Conservation Fund 2009 Approved Projects). are raised. In Spain, B. halimifolia was reported for the first time by Allorge (1941) in the Basque Country (from Lekeitio to Introduced range Deba). The Gobierno Vasco (2011) noted that although the Oceania: Australia (Queensland, New South Wales; Virtual species did not seem to be available in nurseries in the Herbarium of Australia), New Zealand, 2014 Basque country, B. halimifolia was nevertheless found in Note: in New Zealand, according to Webb et al. (1988), gardens in Asturias (Gonzalez Costales, 2007). The species the species was recorded as locally established on Banks is suspected to have invaded some natural areas in the Peninsula (Canterbury) only: Evans Pass, Lyttelton, Victo- Spanish Basque country through natural spread by wind ria Park and Barrys Bay (Lynne Huggins, Department of from the French Basque Country (Estela Beteta, Gobierno Conservation, New Zealand, pers. comm., 2012). Vasco, pers. comm., 2012).

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In Belgium, the plant was mentioned for the first time as introduced in 1924. It is thought to have been introduced intentionally in coastal dunes as a windbreak (Verloove, 2011). This plant is now recorded to be used in soil bioen- gineering systems to stabilize tidal shorelines because of its ability to root from a dormant, unrooted cutting (Invasive Alien Species in Belgium Website). There are only two records of B. halimifolia in the UK, where the plant is known to have occurred since 1942 (Clements & Foster, 1994). The introduction of the species has been reported more recently in Italy in the Veneto region (Zanetti, 1997; Minelli, 2009; Pizzo & Buffa, 2009) and in the Tuscany region (Coaro, 1987; Arrigoni & Viegi, 2011), in both cases in coastal areas. Fig. 2 Female inflorescence of Baccharis halimifolia. © Guillaume Fried, Anses, FR. Morphology

Plant type Baccharis halimifolia is a branching shrub or small tree growing up to 4 m high.

Description Baccharis halimifolia’s trunk can reach 16 cm in diameter. Its leaves are alternate, pale green, thick (Fig. 1); those of the stem and lower branches are obovate to elliptic or oblanceolate, 2–7 cm long and 1–5 cm wide; those of the branchlets are smaller, cuneate at the base, several-toothed above the middle. B. halimifolia is dioecious. Flowers are small, female ones are whitish (Fig. 2), male ones are Fig. 3 Male flowers of Baccharis halimifolia. © Guillaume Fried, greenish (Fig. 3). Flower heads are situated in terminal or Anses, FR. axillary clusters of 1–5. Achenes are 1–2 mm long, pappus is bright-white, 6–8 mm long (Weber, 2003; Muller, 2004). Biology and ecology

General Baccharis halimifolia is generally an evergreen, but in the cooler parts of its native range, it is deciduous (Sims-Chilton & Panetta, 2011). B. halimifolia grows fast, up to 30 to 40 cm per year (Herrera & Campos, 2010). Shrubs are mature within 2 years and flower every year (Panetta, 1979b). The species reproduces mainly by seeds, but can also reproduce vegetatively by sprouting from the base, fol- lowing disturbance (Westman et al., 1975). B. halimifolia flowers at the end of the summer (August to October in France) and is wind-pollinated. Seeds are produced from October to November (in France). They are abundant, esti- mations range between 10 000 (Auld, 1970) to 1 500 000 per year for a healthy adult plant growing in full sunlight (Westman et al., 1975), and are dispersed by wind, poten- tially over long distances, as well as by water (Fig. 4). Seeds germinateeasily(usuallyin1–2 weeks) if sufficient soil moisture is available (Westman et al., 1975). The seed bank Fig. 1 Leaves of Baccharis halimifolia © Guillaume Fried, Anses. is expected to persist for at least 2 years (Panetta, 1979a).

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Fig. 4 Seeds of Baccharis halimifolia. © Guillaume Fried, Anses, FR. Fig. 5 Baccharis halimifolia fruiting along a river course in the Domaine de la Palissade in Camargue (FR). © Sarah Brunel, EPPO

Environmental requirements Habitats Baccharis halimifolia can be found on a wide range of soil In its native range, B. halimifolia occurs in open sandy types. It grows most typically in moist soils with high places, wet fields, marshes, beaches, disturbed sites, road- organic content (Sims-Chilton & Panetta, 2011). However, sides, old fields, from 0 to 100 metres above sea level in Spain, B. halimifolia was also associated with high (Sundberg & Bogler, 2006). It is considered as a common elevations and coarse sand (Onaindia et al., 2001; cited in species in upland fringes of coastal saline marshes and back Sims-Chilton & Panetta, 2011). The plant is observed on dune habitats (Cronquist, 1980). It is also capable of estab- soils with pH values ranging from 3.6 to 9 (Westman et al., lishing in disturbed habitats such as fallow fields and hedge- 1975). In both its native and exotic ranges, it is often found rows, as well as inland saline soils (Krischik & Denno, in soil covered by water with salinity ranging from 0 to 1990). 3.6% (Westman et al., 1975). In Australia, B. halimifolia established within a wide In its native area, B. halimifolia is found from Florida, variety of plant communities, from dry Eucalyptus forests which has a humid subtropical to tropical climate, to areas to native tea-tree (Melaleuca quinquenervia) swamps such as Massachusetts, which has snowfall in winter (Westman et al., 1975). It is particularly suited to moist (USDA-ARS Website). It covers four plant hardiness zones gullies, salt marsh areas and wetlands. It also grows on from 9 to 6 with mean annual minimum temperatures of high, cleared slopes (Anonymous, 2007a). As in its native À17.8°C/À23.3°C in the latter zone (Ervin, 2009). It is range, B. halimifolia is also found in disturbed habitats, frost tolerant, and can withstand temperatures as low as including cleared unused land, cleared slopes (Anonymous, À15°C (Huxley, 1992 in Muller, 2004). Westman et al. 2007a), tropical pastures, irrigation channels and coastal (1975) found that optimal germination occurs between 15 canals (Westman et al., 1975) or exotic pine plantations, and 20°C with cold pre-treatment at 5°C. This shows the e.g. Pinus elliottii (Panetta, 1979a,b). temperate to subtropical range of the species. On the Atlantic coast of Europe, B. halimifolia is known to escape from cultivation (private gardens, hedges and Uses and benefits roundabouts) and to establish first in artificial habitats: along roadsides, along canals, in agricultural, industrial or The species is reported to be used as a food supplement for on old saltworks wastelands (Le Moigne & Magnanon, its medicinal value and as a cleanser promoting weight loss 2009). From these habitats, it invades coastal wetlands such (Federation des Conservatoires Botaniques Nationaux, as saltmarshes, moist and wet dune slack, water-fringing undated). reedbeds, meadows and open woodlands (Muller, 2004) and humid prairies (Zendoia et al., 2006) (see Fig. 5). It is also Pathways for movement found in drier habitats such as heathlands with Ulex euro- paeus or in the upper beach area (Anonymous, 2007b). It Natural dispersal also invades cliffs (Campos et al., 2004). The main habitats in which B. halimifolia is known to Baccharis halimifolia seeds are very small, their mass is occur in the EPPO region according to the EUNIS habitat approximately 0.11 mg (Panetta, 1977) and they are classification are provided in the EPPO PRA Record for crowned by a pappus and are therefore readily dispersed by B. halimifolia. wind (Boldt, 1987) but also by water (Panetta, 1977).

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maritima (Campos et al., 2004), which is included within Movement in trade the category ‘danger of extinction’ in the ‘Basque Cata- The plant is used as an ornamental and amenity plant due logue of Threatened Species of the Wild and Marine Fauna to its tolerance to salinity. ‘Ornamental’ and ‘amenity’ are and Flora’. Other estuarine species present in invaded rush defined according to Lambdon et al. (2008): marshes such as Cochlearia aestuaria, Frankenia laevis, (1) Ornamental species are cultivated on a small scale Limonium humile, Salicornia spp. or Sarcocornia perennis (especially in private gardens). are already endangered at the regional level in the Basque (2) Amenity species are cultivated on a large to moderate country (Uribe-Echebarrıa & Campos, 2006). Galarza & scale in public places for landscaping purposes (e.g., Hidalgo (2005–2006) also report that the stands of for soil stabilization or aesthetic enhancement). B. halimifolia have an impact on bird populations associ- Trade for ornamental purposes can occur both via the in- ated with invaded habitats. The plant is considered to ternet and by direct retail at the nursery. The plant is reduce the attractiveness and use of the habitats for nesting, widely available in garden centres and nurseries in Europe. roosting and feeding. B. halimifolia is then suspected to threaten Acrocephalus arundinaceus (Acrocephalideae, reg- istered on the Annexe 2 of the Bonn and the Bern Conven- Impacts tions) and Emberiza schoeniclus (Emberizideae, registered on the Annex 2 of the Bern Convention). Effects on plants Concerning social and human health impacts, the estab- In its native range, B. halimifolia is considered a weed as it lishment of B. halimifolia occurs in areas where mosquitoes invades overgrazed rangeland in the Southern United States are present. Dense thickets of B. halimifolia protect mos- (Nesom, 2006). In Australia, B. halimifolia is a pest of pas- quito larvae from insecticide treatments and impede access tures, where thick stands can inhibit the movement of stock for mosquito control (Bouterin & Canonge, 1999 in Muller, and reduce the productivity of grazed areas (Ensbey, 2001). 2004). B. halimifolia is also reported to cause hay fever- Nevertheless, there are currently no records of impacts on type allergies (Moss, 1967; cited in Panetta, 1979b; pastures in the EPPO region. DeLoach et al., 1986) caused by airborne pollen and seed ‘fluff’ (Anonymous, 2007a). Moreover, as B. halimifolia is highly flammable its establishment in fallow lands may Environmental and social impact increase the fire hazard and threaten security (on industrial Baccharis halimifolia can outcompete other plants. It forms sites for instance) (Muller, 2004; Invasive Alien Species in dense monospecific stands that are persistent as each shrub Belgium Website). When established near salt marshes, can live up to 25 years, and can have detrimental impacts on B. halimifolia is detrimental to salt production as it forms a native populations and communities. Once established, the wind break and contaminates salt with seeds (David, 1999). shrub blocks the light to other species, modifying micro-cli- As the species is difficult to control, management costs matic conditions, leading to a regression of herbaceous spe- are quite expensive. To give an indication, the manual pull- cies (Muller, 2004). Studies conducted at the habitat scale ing out of plants coupled with the use of herbicide over demonstrate that B. halimifolia significantly reduces the spe- 298 ha cost 630 000 EUR in 2011 in the framework of the cies richness (Pierre, 2012; Fried et al., in press). Invasion Basque country Life + project (LIFE project 08NAT/E/ by B. halimifolia also leads to a marked change in the struc- 000055 Website). ture and physiognomy of the invaded community (Campos et al., 2004). B. halimifolia can also cause physical modifi- Control cations of habitats. As leaves and wood of B. halimifolia secrete an inflammable resin (Bean, 1981), dense thickets of The first step in controlling B. halimifolia is the reduction B. halimifolia could increase fire frequency in invaded habi- of its use as an ornamental plant, in particular along roads. tats (Muller, 2004). Lozano Valencia & Alagon Cardoso Flooding with marine water could limit the spread of the (1995) report modifications in productivity and in nutrient species. Nevertheless, such a technique can only be consid- cycling, including changes in the rates of erosion and sedi- ered in salt marshes (Muller, 2004). mentation of the affected estuaries. Such impacts are Cutting and uprooting can locally control the plant, but recorded to occur in threatened habitats listed in the Annex I these expensive measures have to be repeated several times of the EC Habitats Directive (Directive 92/43), in particular because of the resprouting ability of the species, and its in France and in Spain (e.g. Atlantic salt meadows, Mediter- large seed bank. If plants are removed manually, the roots ranean salt meadows, Mediterranean and thermo-Atlantic should be cut well below the soil surface to prevent respro- halophilous scrubs, Embryonic shifting dunes, see the EPPO uting. When uprooting is not possible, regularly cutting the PRA record for B. halimifolia for further details). shrubs before they set seeds can stop the spread of the In addition, B. halimifolia may threaten rare or vulnera- plant. Sheep grazing can reduce the spread of B. halimifolia ble species. In the Spanish Basque country, B. halimifolia locally, when there is a heavy pasture load (the species has is thought to have reduced the populations of Matricaria a low palatability) (Muller, 2004; Charpentier et al., 2006).

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Chemical control is providing satisfactory results with Coaro E (1987) Flora e vegetazione del Bosco dell’Ulivo (Parco di 2,4-D, dicamba plus MCPA, glyphosate, picloram plus Migliarino, S. Rossore e Massaciuccoli). Quaderni del Museo di – 2,4-D, and tryclopyr (Weber, 2003). Storia Naturale di Livorno, 8(Suppl. 1), 1 45 (in Italian). Correll DS & Correll HB (1982) Flora of the Bahama Archipelago. Control through fire has proven to be inefficient (Muller, Cramer J, FL-9490 Vaduz, Germany (DE). 1692 pp. 2004). Several biological control agents have been tested, Charpentier A, Riou K & Thibault M (2006) Bilan de la campagne de but are not regarded as highly efficient. controle^ de l’expansion du Baccharis halimifolia menee dans le parc naturel regional de Camargue (PNRC) en automne 2004 et 2005 (in French). Regulatory status Cronquist A (1980) Vascular flora of the Southeastern United States. University of North Carolina Press, Chapel Hill, North Carolina In Spain, B. halimifolia is registered on the Catalogue of (US). Invasive Alien Species for which introduction, possession, David C (1999) Etude du Baccharis halimifolia dans les marais salants trade and transport of the species listed is prohibited de Guerande et du Mes. Note de synthese du rapport de stage pour le (Ministerio de agricultura, alimentacion y medio ambiente, Syndicat Intercommunal de la Cote^ d’Armor et de la presqu’^ıle Boletın Official de Estado, 2011). Guerandaise, Guerande (FR), 41 pp (in French). Baccharis halimifolia has been declared an unwanted DeLoach CJ, Boldt PE, Cordo HA, Johnson HB & Cuda JP (1986) Weeds common to Mexican and U.S. rangelands: Proposals for organism under the New Zealand Biosecurity Act 1993, biological control and ecological studies. In: Proceedings of the which makes it illegal to knowingly release, spread, display Symposium on Management and Utilization of Arid Land Plants, or sell, breed, propagate or otherwise distribute plants or Saltillo, Mexico, 18–22 February 1985 (Ed. Patton DR), pp. 49À67. part thereof. Rocky Mountain Forest and Range Experiment Station, Fort Collins In Australia, the species is considered noxious and is reg- (US).  ulated in Queensland and New South Wales (as well as in Duhamel du Monceau HL (1800) Traite des arbres et arbustes que l’on cultive en France. Seconde edition, considerablement augmentee; Northern Territory where it is not recorded as present) [Tome premier]. 2 Edition. Didot aine, Paris (FR) (in French). (Weeds Australia Database). Dupuis A & Herincq F (1884) Horticulture. Veg etaux d’ornements. Abel Pilon et Cie Editeurs, Paris, France (FR). Ensbey R (2001) Groundsel Bush. NSW Agriculture, Grafton (US) References (in French). Ervin GN (2009) Distribution, habitat characteristics, and new county- Allorge P (1941) Essai de synthese phytogeographique du Pays Basque. level tecords of Baccharis halimifolia L. on a portion of its present Bulletin de la Societ e Botanique de France 88, 66 (in French). US range boundary. Southeastern Naturalist 8, 293–304. AME & CBNMP (2003) Plantes envahissantes de la region Federation des Conservatoires Botaniques Nationaux (undated) Mediterraneenne. AME, ARPE, 42 p. Baccharis halimifolia. 6 pp. http://invmed.fr/sites/invmed.fr/files/ Anonymous (2007a) Fact sheet. Groundsel bush (Baccharis pictures/Fiche%20-%20Baccharis-halimifolia_sr.pdf halimifolia). Biosecurity Queensland, Department of Primary Flora of North America, Vol. 20, Baccharis halimifolia. http://www. 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