Quick Facts

Quick facts

• Originally from Europe and western Asia, Taurian Thistle (Onopordum tauricum) is a large spiny thistle with large flower-heads and purple flowers.
• 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.
• Colonises bare and degraded areas, so heathy dense pastures prevent most establishment and survival of seedlings. 
• Controlled via physical methods and herbicides, and good cultural practices.

What Does It Look Like?

What is it?

Taurian Thistle (Onopordum tauricum) is a biennial herb, initially forming a basal rosette, before producing an erect spiny winged stem(s) to 2 metres tall. Basal (rosette) leaves are without a stalk up to 250 mm long and 100 mm wide. Stem leaves are sessile (without a leaf-stalk), and leaves decrease in size the further up the stem they produced. All leaves are oblong-lanceolate (oblong, length a few times greater than width, with sides almost parallel and ends rounded); (lanceolate, lance, shaped, about 4 times as long as broad, broadest in the lower half and tapering to the tip). Leaf blades are divided into 6-8 pairs of triangular lobes which are tipped with [many] a yellow spine. Leaves are green, the upper surface sparsely glandular hairy, lower surface more densely hairy to cobwebbed. The stems are ribbed and winged, with sparse glandular and multicellular hairs, with wings are up to 15 mm wide with 5 mm spines on the lobes.

The purplish-pink flower-heads are on short stalks, solitary or several clustered at the end of the branches, near or at the top of the plant. They are more or less globose in outline, 55 – 70 mm diameter with each flower-head surrounded by several rows of green or purplish floral bracts (modified leaves), lanceolate, 20–30 mm long , the outer row tapering to a stout spiny tip. The flowerheads contain numerous slender purplish-pink flowers. Individual flowers are longer than the floral bracts (about 25-35 mm long) and each forms one seed (cypselas) with several hundred seeds produced per flower-head .

The fruits or 'seeds' (cypselas) are 5-6 mm long, 4-ribbed, wrinkled, shiny and brown, with a whitish pappus on top comprised of barbellate soft bristles 8-10 mm long cream in colour (Jeanes 1999; Vic Flora 2016).

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

Flower colour

Purple, Pink

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

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

Are there similar species?

Scotch Thistle (Onopordum acanthium) and Illyrian Thistle (Onopordum illyricum) both have similar general growth habits to Taurian Thistle (O. tauricum) but differ in having stems and leaves that are whitish with woolly hairs, whilst Taurian Thistle has green leaves with sparse glandular hairs and green to brownish stems. The fourth species of Onopordum in Australia, Stemless Thistle (O. acaulon), produces a rosette of white woolly-hairy leaves and then flowers without ever elongating (Slee 2007, pers. comm.).

Taurian Thistle differs from Nodding Thistle (Carduus nutans) in having less deeply divided leaves with fewer spines (the leaves are deeply divided and extremely spiny in nodding thistle). Also inside the flower-heads the receptacle (on which the numerous individual flowers develop) is not pitted in any species of Carduus, and is deeply pitted in all species of Onopordum (easiest to see in heads from which all seed have fallen) (Slee 2007, pers. comm.).

Why Is It A Weed?

What are its impacts?

Taurian Thistle (Onopordum tauricum) 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. Could seriously impact agricultural and other disturbed areas including native vegetation and urban areas.

Agriculture: Taurian Thistle has the potential to become a serious agricultural weed, especially in marginal or overgrazed areas or and bare patches and disturbed sites /  It will occupy 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 large mammals to foraging and watering areas and may harbour 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). It is possible that Taurian Thistle could contaminate wool, similarly to the related (Onopordum acanthium & O. illyricum) (DPI 2007)

Native ecosystems: Although thought to be a serious weed of agriculture, Taurian Thistle could also invade open native vegetation and degraded and disturbed vegetation. 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). 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 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).

Urban areas: Could impact roadside and parks and gardens, and abandoned areas around habitations and towns. Large dense infestations can form impenetrable stands which restrict access of people to recreation areas.

How does it spread?

There is no information currently available on the dispersal of Taurian Thistle. It reproduces entirely by seed. It is a prolific seed producer  with each flower-head 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.).

What is its history in Australia?

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).

How To Manage It?

Best practice management

Hand-hoeing and herbicide application have been effective in reducing Taurian Thistle (Onopordum tauricum) infestation from an infestation of 15 ha over an area of 150 ha of pasture in 1984 to about 60 plants in 1999. By 2001 the numbers were even further reduced (Groves et al. 2002). The many control methods for other Onopordum species can be used for Taurian Thistle.

Chemical control: Herbicide control of these three Onopordum species can be very effective and is an essential part of the overall management of these thistles and are used on large or dense infestations applying . However, plants can be tricky  to kill  because of the difficulty in wetting the woolly-hairy leaves of the plants. To achieve an effective kill the following should be considered; Timing of application is also important. If a single application of herbicide is undertaken then a springtime application is best (Dellow 1996), as herbicides are most effective on seedlings and young rosettes, Once plants begins stem elongation, herbicides may be less effective; The hairy leaves of the thistles can reduce herbicide effectiveness through reduced absorption. Therefore it is important to follow the herbicide label and use the recommended rate, application volume and adjuvant; Control will be reduced if plants are stressed. When there is a low density of thistles spot spraying  is preferred (DPI NSW 2019). Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information available at http://www.apvma.gov.au 

Non-chemical control: Physical control:  Because Taurian Thistle requires open space to establish and generally establishes in highly disturbed ecosystems reducing stock levels and allowing perennial grasses to establish is likely to drastically reduce the establishment of weed seedlings (Healy, Enloe & DiTomaso, 2005).  When there is a low density of thistles hand chipping is effective. Remove as much of the taproot as possible so that regrowth does not occur. Cultivation is effective on seedlings or young rosettes if they are uprooted. Older rosettes are damaged by cultivation but are able to regrow, especially if the soil is moist. Slashing or mowing is not usually effective as plants develop new growth from the base. Immature seed heads that are cut and left lying on the ground can contain viable seed.

Mechanical control: Cultivation is effective on seedlings or young rosettes if they are uprooted. Older rosettes are damaged by cultivation but are able to regrow, especially if the soil is moist. Plants can be mown or slashed before flowering to prevent seed set but this is temporary as plants will regrow and develop new growth from the base. Immature seed heads that are cut and left lying on the ground can contain viable seed and spread seed.

Competition and management: Pasture management is the most important part of any thistle control program is maintaining a dense, vigorous and competitive pasture. A vigorous perennial grass pasture provides competition for germinating thistles, reducing seedling establishment. Gaps in the pasture result in an increase in thistle germination and seedling survival so maintaining excellent ground cover at all times is desirable (DPI NSW 2019).

While thistles respond to increases in soil fertility (and in particular nitrogen), management of all pasture types should aim to maintain pastures that have a good balance of perennial grass to legume content. Fertiliser application (as determined by a soil test) will improve the vigour of annual and perennial introduced grasses, increasing ground cover and reducing future thistle establishment.

Thistles are generally avoided by stock. However goats eat thistles at both the rosette and flowering stage as well as post-flowering and are known to be effective. This can be a vital step as it reduces seed production and thus limits recruitment of new thistle plants and also reduces the build up of seed in the soil. The soil seedbank is relatively long-lived.

Biological control: Taurian Thistle has also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. Weevils were introduced to Australia to control this genus in 1992, but it was found that less than 20% of O. tauricum capitula were attacked (Briese, 2000). Taurian thistles are still capable of seed production under most herbivory pressure (Agriculture Victoria 2021).

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

There is very little information currently available on the life cycle of Taurian Thistle. It is a biennial herb, producing a rosette after germination (probably in autumn-winter-spring). This rosette enlarges in the first summer but does not elongate, flower and set seed until the second spring-summer. After seeding the plant dies (Groves et al. 2002; Healy, Enloe & DiTomaso 2005; Slee 2007, pers. comm.). Further study and observation is required to understand the life cycle of this species.

Where Is It Found?

Which states and territories is it found?

SA, VIC

What areas within states and territories is it found?

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 (AVH 2021; Groves et al. 2002).

There is also a record of Taurian Thistle from Orroroo (mid-north) in South Australia, about 270 km north of Adelaide, that was collected in 1978, from the northern side of road to Pekina. Unfortunately, it is apparently undated and no further information is currently available, and it it unknown if the plant still persists  Further investigation is required in and around the Orroroo area in South Australia (eFlora 2021).

In New South Wales an unconfirmed record exists, reported via Atlas of Living Australia (ALA 2021) with no herbarium collection, locality or other information. 

Where does it originate?

Taurian Thistle is native to western Asia, eastern and south-eastern Europe (GRIN 2007; POWO 2019).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, TAS, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

YES

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Onopordum tauricum

Other scientific names (synonyms)?

Does it have other known common name(s)?

Scotch Thistle