Yellow starthistle [Centaurea solstitialis L][CENSO][CalEPPC: A1][CDFA list: C] Photographs Biocontrol

Malta starthistle or Tocalote [Centaurea melitensis L.][CENME][CalEPPC: B] Photographs

Sicilian starthistle [Centaurea sulphurea Willd.][CDFA list: B] Photographs Map of Distribution

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GENERAL DESCRIPTION: Noxious erect winter annuals (sometimes biennials) with spiny yellow-flowered heads, mostly to 1 m tall. Refer to the table Comparison of yellow-flowered starthistles for a quick review of important differences.

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SEEDLINGS: Cotyledons oblong to spatulate, base wedge-shaped, tip +/- squared. First few leaves typically oblanceolate. Subsequent rosette leaves oblanceolate, entire to pinnate-lobed. Terminal lobes largest. Later rosette leaves to 15 cm long. Hair characteristics are visible with 10-14x magnification.

MATURE PLANT: Stems stiff, openly branched from near or above the base or sometimes not branched in very small plants. Stem leaves alternate, mostly linear or +/- narrowly oblong to oblanceolate. Margins smooth, toothed, or wavy. Leaf bases extend down the stems (decurrent) and give stems a winged appearance. Rosette leaves typically withered by flowering time.


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FLOWERS: Heads ovoid, spiny, solitary on stem tips, consist of numerous yellow disk flowers. Heads sometimes closely 2-3-clustered in Malta starthistle. Vigorous individuals of Malta and yellow starthistle may develop flower heads in branch axils. Phyllaries palmately spined, with one long central spine and 2 or more pairs of short lateral spines. Insect-pollinated.

FRUITS and SEEDS: Achenes (seeds) +/- barrel-shaped, +/- compressed, laterally notched at the base. Pappus bristles slender, stiff, unequal.

POSTSENESCENCE CHARACTERISTICS: Stems with old flower heads turn gray-brown and can remain intact for over a year.

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HABITAT: Open, disturbed sites, grasslands, rangeland, open woodlands, fields, pastures, roadsides, waste places. Yellow and Malta starthistle also occur in cultivated fields.


PROPAGATION/PHENOLOGY: Reproduce by seed. 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. Most 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.

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MANAGEMENT FAVORING/DISCOURAGING SURVIVAL: Monitoring and spot eradication of plants when they are discovered can prevent the spread of starthistles.

SIMILAR SPECIES: Unlike yellow, Malta, and Sicilian starthistle, purple starthistle [Centaurea calcitrapa L.] and Iberian starthistle [Centaurea iberica Spreng.] have purple flowers, upper stem leaves mostly pinnate-divided, and straw-colored spines in the center of the rosettes.

CONTROL METHODS: A very large compendium of biology, ecology and control information has been compiled by Dr. Joseph DiTomaso at the University of California Davis. The information can be accessed via the world wide web at the following address:


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