Quick Facts

Quick facts

• Originally from Europe, western Asia and northern Africa, Spear Thistle (Cirsium vulgare) is an erect spiny plant to 1.5 metres tall with spiny leaves, spiny winged stem, and purple flowers surrounded by bell-shaped spiny bracts.
• Reproduces by seed, spread by water and in soil attached to machinery and vehicles, and in soil and agricultural produce. 
• Seed production is very high. Seeds germinate in two main periods, autumn and late winter/spring and plants remain at the rosette stage until a chilling period has been experienced.
• A highly competitive agricultural weed on fertile soils in temperate Australia.
• Can cause serious loss of production on normally productive farmland.
• The most effective form of control is prevention of establishment by the maintenance of a healthy perennial pasture at all seasons, but particularly in summer going into autumn when the weed mostly germinates.
• Can be effectively controlled by use of herbicides.

What Does It Look Like?

What is it?

Spear Thistle (Cirsium vulgare) is an erect annual or biennial spiny rough herb, 600 mm to 1.5 m tall with a branching taproot to 700 mm deep. The plant initially forms a basal rosette (radiating cluster) of short-lived spiny leaves, 350 mm long  and and 100 mm wide, with a short leaf stalk (obscurely petiolate), obovate (egg-shaped attached to the stem at the thinner end) to lanceolate (lance shaped, about 4 times as long as broad, broadest in the lower half and tapering to the tip). Rosette leaves are toothed to pinnately lobed, margins spiny, upper leaf-surface dark green and rough to touch covered with small prickles warts and some hairs, lower surface white-tomentose (a dense covering of short, woolly hairs) or cobwebbed. The stem elongates, sometimes remaining un-branched, otherwise branching in the upper part, with stem leaves. The stem leaves are similar to rosette leaves just smaller to to 250 mm long, stem leaves decurrent (leaf base extends down the stem) as a deeply lobed and very spiny wing.

The flower heads are bell-shaped with flower flowers emerging at the top, borne at the ends of the stem and branches on stalks either solitary or in clusters of 2–3 together (a well branched plant may have over 100 flower heads). Flower heads are 30-50 mm long and consist of several rows of spiny green floral bracts (modified leaves) arranged more or less flask-shaped, involucre (overlapping leaf-like structures surrounding the dense clusters of flowers) are about 25 mm long; intermediate bracts linear-lanceolate, erect to recurved, with a straight terminal spine 2–5 mm long with the inner bracts longer and narrower, acute (sharply pointed; converging edges making an angle of less than 90°). A single flower head may contain up to 280  slender tubular purple to pink (rarely white) flowers 25–35 mm long emerging at the top of bracts. Each flowers develops a single seed also known as a cypselas. Flowers mostly summer and autumn

The fruits or 'seeds' (cypselas) are about 3–6 mm long and 1.5 mm wide, smooth, grey to light brown or almost black, with faint longitudinal markings, and bear a pappus of soft feathery hairs 2–2.5 cm long at the top. This pappus is less easily dislodged from the seed when the seeds are ripe compared with some other species of thistle, but for many seeds the pappus is still lost before the seed is shed from the head (Parsons & Cuthbertson 1992; Klinkhamer & de Jong 1993; Bruzzese 1996).

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

Flower colour

Purple or Pink

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Spear Thistle is found in subhumid to cool temperate areas of temperate and subtropical Australia from the coast to subalpine regions but only ever sporadically in drier, more inland areas. In tropical north-eastern Australia it is limited to upland areas (altitudes over 800 m). In southern Australia it is abundant being favoured by the Mediterranean climate with rainfall 500–900 mm per year, fertile soils and open sunny sites. It is found in pastures (including irrigated pastures), cropland (including irrigated crops), on roadsides and neglected areas, but is also known to occur on less fertile coastal dunes and in heathlands. In areas of natural vegetation it is invasive, but usually where there has been some disturbance (Parsons & Cutherbertson 1992; Slee 2007, pers. comm.).

Are there similar species?

Spear Thistle (Cirsium vulgare) can be distinguished from its sister species Perennial Thistle (Cirsium arvense) by its annual or biennial growth habit and its lack of rhizomatous roots. In addition Perennial Thistle also has much smaller flower heads with male flowers and female flowers occurring on separate plants, compared with Spear Thistle's larger bisexual flowerheads. Perennial Thistle does not have 'wings' along the stems and has short, purple tipped spines on the floral bracts (Navie 2004; Slee 2007, pers. comm.).

Spear Thistle can easily be told from Nodding Thistle (Carduus nutans) by its erect flower head (drooping heads in Carduus nutans) and the greenish coloured, spine-tipped bracts. Nodding Thistle has dropping flowerheads and purplish coloured bracts (Navie 2004).

Spear Thistle may also be confused with the Slender Thistles (Carduus pycnocephalus and C. tenuiflorus). However, these have smaller, slender stalkless (sessile) flowerheads compared with the large, broad, stalked (petiolate) flower heads of Spear Thistle (Navie 2004).

Why Is It A Weed?

What are its impacts?

Spear Thistle (Cirsium vulgare) is mainly a weed of agricultural areas, wasteland, roadsides, open native vegetation and disturbed areas. It competes with sown and desirable species. 

Agriculture: Spear Thistle has a high impact in pastures because of the size, spininess and the competitive ability of the plants for moisture and nutrients. The plants physically deter stock from grazing, out compete valuable pasture plants, reduce carrying capacity, may provide harbour for vermin such as rabbits and can contaminate hay (Parsons & Cuthbertson 1992; DPIW 2002). In addition the spines contaminate wool making shearing difficult and degrading the value of the clip (Parsons & Cuthbertson 1992; DPIW 2002). Spear Thistle spines may transmit virus diseases between animals.

It is valuable to the honey industry as it produces a good supply of nectar and pollen (Parsons & Cuthbertson 1992).

Native ecosystems: In areas of natural vegetation it is invasive, but usually where there has been some disturbance (Parsons & Cutherbertson 1992; Slee 2007, pers. comm.). It invades disturbed native grasslands, open woodlands and conservation areas.

Urban areas: A weed of gardens and urban parks, roadsides and neglected sites.

How does it spread?

Spear Thistle seeds are spread short distances by the wind. The feathery pappus attached to the seed does aid in this, but for many seed produced the pappus detaches from the seed before leaving the flower head. Seed with pappus intact have been measured as being dispersed more than 30 m from the parent but the majority end up within 2 m (Parsons & Cuthbertson 1992; Klinkhamer & de Jong 1993).

Most seed is dispersed by machinery, vehicles, flowing water, livestock, contaminated seed and fodder (Parsons & Cuthbertson 1992; Klinkhamer & de Jong 1993).

What is its history in Australia?

Spear Thistle is known to have occurred in Tasmania as early as the 1830s and was introduced from there to South Australia by 1841. It was one of the weeds included in the Victorian noxious weeds legislation in 1856. It was one of the first weeds to establish after bushland clearing and was likely spread through using contaminated pasture seed (Parsons & Cuthbertson 1992).

The first known herbarium records from Australia are from; Tasmania in 1878; Victoria in 1884; New South Wales in 1887; South Australia in 1903; Queensland in 1910; Western Australia in 1922; ACT in 1922.

How To Manage It?

Best practice management

Spear Thistle (Cirsium vulgare) is mainly controlled by herbicide application and can be managed by cultivation. Not eaten by cattle or sheep, but eaten by goats. In pastures, the most effective form of control is maintenance of a healthy perennial pasture at all seasons, but particularly in summer going into autumn when the weed mostly germinates.

Chemical control: Spear Thistles at the seedling stage are susceptible to growth regulator type herbicides. When practicable, spraying should be completed before the centre flowering stem develops. Although Spear Thistle remains reasonably susceptible even up to flowering, treatment at this late stage involves the use of more active forms of the herbicides and of higher application rates, with a consequent risk of greater pasture legume damage (DPIW 2002).

In years when there is an early autumn break and large numbers of thistles germinate before the temperature falls, autumn spraying can be very effective. Spraying at this time also requires lower herbicide rates, is less damaging to clover and allows the desirable pasture species to grow with reduced competition from the thistles (DPIW 2002).

In most winters when the temperature falls to near freezing, Spear Thistles become dormant and very much less susceptible to herbicides. Susceptibility increases again with the onset of spring growth and spraying can usually be resumed effectively in September or October (DPIW 2002).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au.

Non-chemical control: Physical control: Single or small population can be chipped out by hand, removing most of the roots.

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

Spear Thistle behaves as an annual or biennial. Seeds may germinate at any time of the year but do so predominantly in autumn after rain with a second germination peak in late winter/early spring. After germination and establishment the plant forms a rosette and then, after experiencing a cold lengthy period, will elongate to form an erect flowering stem which sets seed and dies. Because of its ability to germinate whenever moisture is available and warmth is adequate infestations of Spear Thistle will usually have plants showing a range of growth stages (Bruzzese 1996).

Seed production is very high but a high proportion of that seed germinates in the year following production (Bruzzese 1996).

Plants germinating in autumn will elongate in spring, flower in summer then set seed and die. They are winter annuals with a 6–9 month life cycle (Bruzzese 1996).

Plants that germinate in late winter/early spring will form a rosette that grows over summer, autumn and winter, then flower the next summer, set seed and die. These are biennials with a 12–15 month life cycle (Bruzzese 1996).

Rarely plants germinating in summer and forming a rosette may flower in the autumn presumably after experiencing a cold snap. These are summer annuals (Bruzzese 1996).

Where Is It Found?

Which states and territories is it found?

ACT, NSW, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Spear Thistle has been recorded in all states and territories of Australia, however, occurrence in the Northern Territory seems to be limited to the urban area of Alice Springs, and no naturalised populations have as yet been recorded (AVH 2021; Parsons & Cuthbertson 2001; DPI 2007; Hussey et al. 1997).  It can be very common and widespread in areas where it has naturalised. 

In New South Wales Spear Thistle is widespread on the coast, tablelands and western slopes, and also in the Riverina, but sporadic and opportunistic in drier more inland areas.

In Queensland it occurs commonly in the warm temperate south-east but only sporadically north of there (e.g. on the Atherton Tableland).

In South Australia it is found in the wetter, more productive south-east of the state especially the Southern Flinders Ranges, Lofty Ranges, Murray region, Fleurieu Peninsula, South-east, Yorke Peninsula and Eyre Peninsula, but occurs only sporadically in the more arid northern Flinders Ranges and is absent from other arid areas.

In Tasmania it occurs throughout the state but most abundantly in the Midlands.

In Victoria Spear Thistle is very widespread from the coast to the sub-alpine being absent only from the driest areas of the north-west of the state.

In Western Australia it is widespread in predominantly arable agricultural areas from Geraldton south to Esperance.

Where does it originate?

Spear Thistle is native to Europe, western Asia (i.e. Eurasia) and northern Africa (Navie 2004; POWO 2019).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

VIC

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?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Cirsium vulgare

Other scientific names (synonyms)?

• Carduus lanceolatus L.
• Carduus vulgaris Savi
• Cirsium lanceolatum (L.) Scop.
• Cirsium vulgare (Savi) Airy Shaw
• Cnicus lanceolatus (L.) Willd.
• Cirsium lanceolatum Hill (misapplied by Domin, K. 1930, Beitrage zur Flora und Pflanzengeographie Australiens. Bibliotheca Botanica. 22(89): 1241.)
• Carduus pratensis auct. non Huds.: Rodway, L. (1903), The Tasmanian Flora: 96

Does it have other known common name(s)?

Black Thistle, Scotch Thistle