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Taxonomic name: Centaurea melitensis Synonyms: Common names: coix de Malte (French), Maltese star thistle (English), Malteser Flockenblume (German), napa thistle (English), tocalote (English) Organism type: herb Centaurea melitensis is a herb of the family Asteraceae. C. melitensis is native to Africa and Europe and was introduced to the United States. It is a highly competitive species that forms dense, impenetrable stands that displaces native and desirable vegetation. C. melitensis usually invades open, disturbed sites and is often spread by humans and livestock via transportation of contaminated crop seed or hay. Description DiTomaso (2001) states that C. melitensis is an erect winter annual with a spiny, yellow-flowered head that typically reaches 1m tall. The stems are stiff and openly branched from near or above the base or sometimes not branched in very small plants. Stem leaves are alternate, and mostly linear or narrowly oblong to oblanceolate. Margins are smooth, toothed, or wavy, and leaf bases extend down the stems (decurrent) and give stems a winged appearance. Rosette leaves typically are withered by flowering time. Similar Species Centaurea solstitialis, Centaurea sulphurea More Occurs in: agricultural areas, natural forests, range/grasslands, ruderal/disturbed Habitat description DiTomaso (2001) states that C. melitensis occurs in open, disturbed sites, grasslands, rangeland, open woodlands, fields, pastures, roadsides, and waste places. C. melitensis also occurs in cultivated fields. Seedlings are more likely to establish in soils with deep silt loam and loam with few coarse fragments (Larson and Sheley 1994, in DiTomaso, 2001). General impacts When star thistle infestations are high, native species can experience drought conditions even in years with normal rainfall (Gerlach et al., 1998, in DiTomaso, 2001). It has also been observed to significantly reduce the seed production of the endangered plant species Acanthomintha ilicifolia (E. Bauder, unpublished data, in DiTomaso, 2001). Uses DiTomaso (2001) states that C. melitensis is used for medicinal purposes in Spain. Notes DiTomaso (2001) notes that C. melitensis was introduced during the 1700's from southern Europe. Wild oat (Avena spp.) litter appears to have allelopathic properties that reduce C. melitensis seed germination. Geographical range Centaurea melitensis is native to Africa and Europe (USDA-ARS 2003). Known introduced range: It is found to be invasive along the western coast and elsewhere in the United States (USDA-NRCS 2003). Introduction pathways to new locations Agriculture: Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Road vehicles (long distance): Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Translocation of machinery/equipment: Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Transportation of domesticated animals: Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Transportation of habitat material: Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Local dispersal methods Agriculture (local): Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Consumption/excretion: Birds such as pheasants, quail, house finches, and goldfinches feed heavily on yellow starthistle seeds and are capable of long distance dispersal (Roché, 1992, in DiTomaso, 2001). Hikers' clothes/boots: The short, stiff, pappus bristles are covered with microscopic, stiff, appressed, hair-like barbs that readily adhere to clothing, hair and fur (DiTomaso, 2001). On animals: Birds such as pheasants, quail, house finches, and goldfinches feed heavily on yellow starthistle seeds and are capable of long distance dispersal (Roché, 1992, in DiTomaso, 2001). On animals (local): Seeds fall near the parent plant or are dispersed to short distances with wind and to greater distances with human activities, animals, water, and soil movement (DiTomaso, 2001). Road vehicles: Human influences, including vehicles, contaminated crop seed or hay, road maintenance, fill dirt or gravel materials, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Translocation of machinery/equipment (local): Human influences, including vehicles, contaminated crop seed or hay, road maintenance, and moving livestock, can also contribute to rapid and long distance spread of the seeds (DiTomaso, 2001). Transportation of habitat material (local): Seeds fall near the parent plant or are dispersed to short distances with wind and to greater distances with human activities, animals, water, and soil movement (DiTomaso, 2001). Water currents: Seeds fall near the parent plant or are dispersed to short distances with wind and to greater distances with human activities, animals, water, and soil movement (DiTomaso, 2001). Management information DiTomaso (2001) states that management strategies are undocumented for Centaurea melitensis but that methods used to control yellow star thistle (Centaurea solstitialis) can be applied. Biological: DiTomaso (2001) states that high-intensity, short-duration grazing can be implemented. Physical: Also, mowing can be very effective, but the timing is extremely important. Mowing too early can result in high seed production. Prescribed burns can provide control, but timing is again important. Much like mowing, a burn at the wrong time may enhance star thistle survival. Monitoring and spot eradication of plants when they are discovered can also prevent the spread of star thistles. Hand pulling or grubbing, removing as much root as possible, may be useful in eradicating small infestations. Reproduction DiTomaso (2001) reports that C. melitensis is insect-pollinated and reproduces by seed. Seed production is highly variable. Plants can produce 1-60 or more seeds per head and 1-100 heads or more per plant. Lifecycle stages DiTomaso (2001) states that most C. melitensis seeds germinate after the first fall rains. Plants exist as basal rosettes through winter and early spring until flowering stems develop in late spring or early summer. Young seedlings are especially resistant to the effects of fall drought. Reviewed by: Susan Donaldson, Ph. D. Water Quality Education Specialist University of Nevada Cooperative Extension. USA Principal sources: Yellow Starthistle Information (DiTomaso, 2001) Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) To contribute information, please contact Shyama Pagad. Last Modified: Friday, 24 June 2005