Carduus pycnocephalus L., Asteraceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  yes

Common name(s): [more details]

English: compact-headed thistle, Italian plumeless thistle, Italian thistle, shore thistle, slender thistle, slender winged thistle

Habit:  herb

Description:  "Annual herbs 5-10 dm tall; stems arachnoid pubescent, spiny-winged throughout.  Leaves oblanceolate to oblong-lanceolate, upper surface sparsely pubescent, lower surface arachnoid-woolly, 8-25 cm long, 2.5-6 cm wide, pinnatifid, with 2-5 pairs of lobes, margins spiny, the spines up to 12 mm long, base decumbent for entire internode.  Heads 1-3 in clusters; involucre cylindrical, 1.5-2 cm long, 0.7-1.3 cm in diameter, arachnoid pubescent, the outer bracts spine-tipped, the inner ones up to 1.3 times as long as the middle ones, faintly 3-nerved, attenuate; corollas purple, 10-14 mm long; pappus 10-14 mm long.  Achenes 4-5 mm long, compressed, smooth"  (Wagner et al., 1999; p. 284).

Habitat/ecology:  "Grassland, scrub, woodland, disturbed places.  In the native range, this highly variable species grows on stony hillslopes, in coastal scrub and disturbed places.  Once established where introduced, it can become dominant and exclude native species.  In savannas, it can carry grass fires to tree canopies and thus increases fire hazards"  (Weber, 2003; p. 85).

In Hawai‘i, "naturalized in dry sites, 1,340-2,130"  (Wagner et al., 1999; p. 284).

Propagation:  Seed.  Fruit production is prolific and the long-lived seeds may remain viable up to 10 years  (Weber, 2003; p. 85).

Native range:  Europe (Wagner et al., 1999; p. 284).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 284) Voucher cited: Wagner 5657 (BISH)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Chile (continental) Chile	Chile (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 66)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 300) "Waste land, pasture, riverbeds, roadsides, railway yards, tussock grassland".

Control: 

Physical:  "Hand pulling is possible, but the root must be cut at least 10 cm below ground level to prevent regrowth.  Mowed plants can regrow fast and still produce seeds.  Grazing by sheep or goats has been proved to be effective".

Chemical:  "Chemical control is done by herbicides containing glyphosate, picloram, or 2,4-D"  (Weber, 2003; p. 85).

Additional information:  Environmental Stewardship Abstract from The Nature Conservancy

Additional online information about Carduus pycnocephalus is available from the Hawaiian Ecosystems at Risk project (HEAR).

Taxonomic information about Carduus pycnocephalus may be available from the Germplasm Resources Information Network (GRIN).

References:

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

U. S. Government. 2006. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2007. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.