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Berkheya rigida

Description
 

African Thistle (Berkheya rigida) is a rigid, spiny perennial (long lived) herb or subshrub growing to 60 cm or sometimes to 80 cm high. Its upright or spreading stems are spineless, rather woody and often whitish and hairy (becoming less hairy with age). It possesses rhizomes (creeping underground stems) and often forms colonies by rooting at the nodes (stem joints) when stems come in contact with the soil. The stiff leaves are 3-10 cm long (the rosette leaves are up to 10 cm long while the stem leaves, alternately arranged on the stem, are shorter) and 2-4 cm wide and are deeply dissected, forming lobes. The tips of the lobes have sharp spines and the leaves are blue-green or green and hairless with age above, and whitish and woolly/hairy below. The flower-heads (5-10 mm across) are yellow (composed of numerous small tubular disc florets) and are surrounded by a series of stiff, pointed, leaf-like bracts (modified leaves), that are up to about 12 mm long. Usually there are several flower-heads clustered at the ends of branches. The smooth seeds are cone-shaped, 2.3-3mm long and blackish in colour. The larger end of these seeds is topped with a group of small scales called a pappus (Cooke 1986; Lander 1987; Lamp & Collet 1989; Hussey et al. 1997; Jeanes 1999; Parsons & Cuthbertson 2001; Richardson et al. 2006; Western Australian Department of Agriculture and Food undated).

For further information and assistance with identification of African Thistle, contact the herbarium in your state or territory.

Distribution:

Although African Thistle is not widespread, it can be locally abundant. It occurs in a few coastal areas in south-western Western Australia (including Perth, Bunbury, Hamelin Bay area, Cape Leeuwin and near Augusta), South Australia (Eyre Peninsula, including Ceduna and Port Lincoln) and Victoria (west of Melbourne, including Port Melbourne and Bacchus Marsh) (Cooke 1986; Lander 1987; Lamp & Collet 1989; Hussey et al. 1997; Jeanes 1999; Parsons & Cuthbertson 2001; Richardson et al. 2006; Western Australian Herbarium 2007).

The plant has occurred as an occasional weed of pastures, roadsides and neglected areas on King Island, Tasmania, but these populations are reported to have been eradicated and there is ongoing monitoring of the sites (Tasmanian Department of Primary Industries and Water 2008).

Habit:Herb
Key points:

  • African Thistle (Berkheya rigida) is a stiff, spiny, long-lived thistle growing up to 80 cm high with yellow thistle-like flower-heads.
  • Its leaves are divided into narrow lobes, with each lobe being spine-tipped.
  • It spreads by seed, rhizomes and rooting stems.
  • Introduced from South Africa, it now occurs in scattered populations in mainly coastal areas in southern Australia.
  • It invades agricultural and natural areas, impacting on pastures, habitats and biodiversity.

How it spreads:

African Thistle reproduces from, and is spread locally by, rhizomes and rooting stems. Colonies increase in size and density as a result of regrowth from rhizomes and layering of the long stems which take root when they bend downwards and come in contact with the soil. African Thistle is spread across greater distances by seed, which may remain dormant in the soil for years. The seeds are not adapted for wind dispersal as they remain in the head (which functions as a burr) that falls to the ground at maturity. Because of the spiny nature of the burr, it may be caught up in the coats of passing animals and transported in that way, as well as being kicked along by hooves or moved by vehicles. Seeds fall from the burr and are dispersed as it is carried or rolls along (Lamp & Collet 1989; Parsons & Cuthbertson 2001).

Where it grows:

The natural habitat of African Thistle includes the subhumid warm-temperate to subtropical scrublands of southern Africa (Parsons & Cuthbertson 2001). It occurs as a weed in Australia, preferring lighter, sandy soils (e.g. infertile coastal sands) but also found on fertile loams and volcanic clays, growing on roadsides, in pastures and disturbed areas. African Thistle invades natural areas of forest, woodland, dune shrubland, coastal scrub e.g. in rocky foreshore areas and grassland (Lamp & Collet 1989; Jeanes 1999; Parsons & Cuthbertson 2001; Thompson Berrill Landscape Design Pty Ltd 2006; Western Australian Herbarium 2007; Tasmanian Department of Primary Industries and Water 2008).

Flower colour:Yellow
Distribution map:

Parsons & Cuthbertson (2001). Australia's Virtual Herbarium (AVH) (2008). Council of Heads of Australian Herbaria (CHAH). Available at http://www.chah.gov.au/avh/index.jsp 

Impacts:

African Thistle has no feed value, as its spines make it unpalatable to stock. It can form large colonies, consisting of matted stems, which limit pasture growth and available grazing area, reducing the productivity and economic returns of pasture areas. Dense patches can also impact on recreational areas and activities by preventing access to beaches and facilities (Parsons & Cuthbertson 2001).

African Thistle can impact on biodiversity by competing with native species in natural areas, including coastal foreshores, dune areas, scrub and shrubland, tussock grassland and woodland (Carr et al. 1992; Keighery & Longman 2004; Thompson Berrill Landscape Design Pty Ltd 2006; Western Australian Herbarium 2007).

There is the potential for its wider distribution and impacts if African Thistle invades better soils away from the coast (Parsons & Cuthbertson 2001).

Origin:

African Thistle is native to South Africa (Parsons & Cuthbertson 2001).

History:

African Thistle was first noticed in Victoria at Geelong in 1906 and Port Phillip in 1909, and in Western Australia at Hamelin Bay some time before 1914 (Parsons & Cuthbertson 2001). It is thought to have been introduced to Australia (particularly the colony at Hamelin Bay) from South Africa as seed in ballast from ships involved in the early timber trade. Dumped ballast at ports probably resulted in the scattered small colonies of this species in coastal southern Australia (Lander 1987; Lamp & Collet 1989; Hussey et al. 1997; Parsons & Cuthbertson 2001). There is also the possibility that it was transported across the Transcontinental Railway to South Australia from Western Australia (Kloot 1987).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.