Centaurea melitensis L.
Centaurea refers to the medicine man, Chiron, because of the medicinal properties of some of the plants in this genus.
Other Names:Cockspur Thistle
Napa Star Thistle
Yellow Burr Cockspur
Summary:An erect, yellow flowered, lobed leaf, annual to biennial thistle with striped, rough stems up to 1 m tall that have spineless wings near the top. The bracts below the flower head each have short often reddish spine. It flowers from spring to early autumn.
Two. Oval to club shaped with prominent network veins. Short stalk. Tip indented. Base tapered. Hairless.
First leaves:Oval to club shaped, Tip round pointed. Edges toothed. Base tapered. Long hairs on the upper and lower surface.
Leaves:Forms a basal rosette.
Stipules - none.
Petiole - Wing of petiole carries on down the stem but disappears before the next node.
Blade - Dull green to dark green, club shaped. Crisp short fine hairs. 150 mm long, lobed about halfway to the midrib with the terminal lobe the largest and side lobes becoming smaller toward the stem, having deep wave like indentations in the leaf edge. Prominent veins. Edges are rough to touch. Tip of terminal lobe is obtuse.
Stem leaves - Lower leaves similar to rosette leaves. Upper leaves, parallel sided to oblong, 3-10 mm wide by 20-66 mm long, extends down the stem as wings, smooth edges or a few teeth, stiff bristly hairs on top and bottom, glandular.
Stems:Dull to dark green. Striped, stiff rough hairs or woolly. Erect, branched, wiry, 200-1000 mm tall. Winged near top. Wings are not continuous from one node to the next.
Flower head:On the ends of short branches from the upper axils. Heads on branches tend to be single and the terminal ones in a cluster of 2-3. Stalkless, egg shaped 7-10 mm long x 8-10 mm diameter (involucre). with small leaves underneath. Edge (ray) flowers sterile, central (disc) flowers bisexual. Receptacle with dense stiff hairs.
Bracts - Yellowish. Sparse fine short hairs or hairless. Outer bracts have a main spreading spine to 5-10 mm long that is often reddish brown or straw coloured and at right angles to the bract. Lower half of bract has spiny edges that are also often reddish. Inner bracts have papery edges with lance shaped appendages rather than spines.
Ovary - inferior.
Florets - Tubular, yellow, glandular.
'Petals' - Yellow.
Fruit:Achene. Flattened. Egg shaped. Brown with pale stripes, sparsely hairy. Persistent pappus with bristles of uneven length. Pappus may be absent from outer achenes. Longest bristle is about the same length as the fruit or seed.
Seeds:Brown to white-grey. Slightly ribbed. bristly pappus. Seed 3-5 mm long x 1-2 mm wide, pappus 2-3 mm long
Roots:Stout, single, tapering taproot up to 10 mm diameter and occasionally branched.
Key Characters:Yellow florets. Pappus present on at least the central achenes. Leaves that have wings that extend down the stem.
Rough striped stem.
Annual or biennial. Germination starts in autumn and continues through winter. The plant forms a rosette in winter and sends up a flowering head in spring. It flowers from September to January.
Flowering times:September to March in SA.
Spring to summer in NSW.
September to January in Perth area.
September to March in WA.
Seed Biology and Germination:Vegetative Propagules:
Population Dynamics and Dispersal:
Origin and History:
Southern Europe, Mediterranean, Africa and Asia. Cosmopolitan.
Distribution:ACT, NSW, QLD, SA, TAS, VIC, WA.
Courtesy Australia's Virtual Herbarium.
Habitats:Disturbed and over grazed areas.
Soil:Sands to loams.
Calcareous red earths.
Solonized brown soils.
Fodder of moderate palatability during the rosette stage and until flowering commences.
Detrimental:Weed of roadsides, pastures, cultivated and disturbed areas and stock routes.
Toxicity:Suspected of poisoning sheep. May contain an alkaloid.
Treatment:Remove stock from infestation.
Management and Control:Thresholds:
It is usually easily controlled by timely cultivation or grazing management.
Herbicide resistance:Biological Control:
Black Knapweed (Centaurea nigra)
Cornflower (Centaurea cyanus)
Dusty Miller (Centaurea cineraria)
Panicled Knapweed (Centaurea paniculata)
St Barnaby's Thistle (Centaurea solstitialis) has more deeply lobed leaves and the spines around the flower are different lengths and usually yellowish.
Star Thistle (Centaurea calcitrapa)
Creeping Knapweed (Acroptilon repens)
Plants of similar appearance:St Barnaby's Thistle is more vigorous and has a yellow, 30 mm spine on the flower head bracts, rather than a red brown, 10 mm spine. The spines on Maltese Cockspur are arranged like the backbone of a fish whereas those of St Barnaby's Thistles are like the fingers on a hand.
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P91. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P936. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P394. Diagram.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P720. Photo.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P165.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #278.4.
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P666.
McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P30. Diagram.
Moerkerk, M.R. and Barnett A.G. (1998) More Crop Weeds. (R.G and F.J. Richardson, Melbourne). P55. Photos. Diagrams.
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