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Onopordum tauricum

Description
 

Taurian Thistle (Onopordum tauricum) is an erect biennial herb to 2 m tall with winged stems. The wings are up to 15 mm wide with 5 mm spines on the lobes. The stems are ribbed, yellow-brown, with sparse glandular and multicellular hairs. The leaves are sessile (without stalks), oblong-lanceolate in outline, to 25 cm long and 10 cm wide with the blade divided into 6-8 pairs of remote triangular lobes which are tipped with a yellow spine. The leaves are green, the upper surface sparsely glandular hairy and the lower surface more densely so. Flowerheads are on short stalks, solitary or several clustered at the end of the branches. They are more or less globose in outline, 5.5-7 cm diameter with each flowerhead surrounded by several rows of green or purplish floral bracts (modified leaves), the outer row tapering to a spiny tip. The flowerheads contain numerous slender purplish pink flowers. Individual flowers are longer than the floral bracts (ca 25-35 mm long) and each forms one seed (achene). Seeds are 5-6 mm long, 4-ribbed, wrinkled, shiny and brown, with a whitish pappus on top comprised of barbellate bristles 8-10 mm long (Jeanes 1999).

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

Distribution:

In 2001, infestations of Taurian Thistle were confirmed at Euroa and Natimuk in Victoria. These populations were quite restricted in area. The infestation at Goroke, believed to have been there since 1913, was not located and may have disappeared or been eradicated (Groves et al. 2002).

There is also a record of Taurian Thistle from Orroroo in South Australia. Unfortunately, it is apparently undated and no further information is currently available (Bean unpubl. manuscript).

Habit:Herb
Key points:
  • Taurian Thistle (Onopordum tauricum) is a sleeper weed, known from western Victoria for at least 90 years. It has not become a widespread weed, being only ever recorded for 3 localities, but has persisted locally in two of these for some time.
  • A record of the species from near Orroroo in South Australia requires urgent investigation.
  • The species is a biennial herb not producing seed until the second summer after germination. Precise details of the life history of the species are not well known and further study is required.
  • The potential of Onoporum tauricum to hybridize with other Onopordum species should be investigated, bearing in mind the weediness of mixed populations of Scotch Thistle, Illyrian thistles and hybrids between them in southern New South Wales.
How it spreads:

There is no information currently available on the dispersal of Taurian Thistle. It reproduces entirely by seed. It is a prolific seeder with each flowerhead producing up to several hundred seeds each .The species has seed with a terminal pappus and may be wind dispersed a short way. In other species of Onopordum the pappus is easily dislodged from the seed and many seed simply fall out of the head near the base of the parent plant. Wider dispersal is likely by contaminated fodder, livestock, machinery and vehicles similar to other thistle species (DPI 2007; Slee 2007, pers. comm.).

Where it grows:

Taurian Thistle is a weed of pasture and rangelands in south-eastern Australia (Cunningham & Brown 2006).

Flower colour:Purple, Pink
Distribution map:

http://www.chah.gov.au/avh/index.jsp 

Impacts:

Taurian Thistle is one of seventeen sleeper weeds identified by the Bureau of Rural Sciences (following consultation with the Australian Weeds Committee) which could have nationally significant impacts on agriculture if allowed to spread. Taurian Thistle has the potential to become a serious agricultural weed, occupying space in pasture, deterring grazing animals and humans, contaminating fodder, invading grain crops reducing growth and contaminating marketable grain.

Severe infestations can form tall, dense, impenetrable stands which restrict access of people to recreation areas, large mammals to foraging and watering areas and may harbour small pest species. The spiny leaves and stems deter most herbivores except maybe goats (which graze on related spiny thistles like Onopordum illyricum). It may have a major impact on the carrying capacity of infested pasture land by more than 5% (Healy, Enloe & DiTomaso 2005; RBWD 2005; DPI 2007).

In grassland and open scrub, where this plant invades the dried vegetation adds to the fuel load, most likely causing a moderate increase in the intensity of fires (Davis 1975; DPI 2007).

Taurian Thistle seedlings do not compete well with established perennial grasses. It requires open space to establish and establishes in highly disturbed ecosystems. It is therefore unlikely to have a major impact on intact ecosystems (Healy, Enloe & DiTomaso 2005; DPI 2007). In grasslands and open scrub it can strongly compete with native plants for resources and may have a minor impact on the forb and herb layers, but not on the shrub layer ecosystems (Healy, Enloe & DiTomaso 2005; DPI 2007).

This plant will reduce the amount of native vegetation growing and also its availability as a food source to native animals. Infestations may reduce the number of animals in a local area (DPI 2007)

It is possible that Taurian Thistle could contaminate wool, similarly to the related O. acanthium & O. illyricum) (DPI 2007)

Origin:

Taurian Thistle is native to western Asia, eastern and south-eastern Europe (GRIN 2007).

History:

The time of arrival of Taurian Thistle in Australia is unknown. To date it has been recorded from only 3 localities in Victoria: Goroke, Natimuk and near Euroa. The Goroke population was first recorded in 1913, the Natimuk infestation from 1964 while the Euroa infestation was recorded in 1984 (Groves et al. 2002).

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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.