spear thistle

Cirsium vulgare
Herb
Basal
Simple
Purple
Green

A short-lived herbaceous plant usually growing 60 to 120 cm tall, but sometimes reaching up to 2 m in height. Its forms a basal rosette of leaves at first, followed by upright and much-branched stems. Its stems are spiny, winged, and usually have a covering of woolly white hairs. Its leaves (up to 45 cm long and 10 cm wide) are usually deeply lobed, with their margins armed with spines. Its purpish flower-heads (3-5 cm across) are enclosed in numerous spiny bracts. Its greyish or light brown 'seeds' (2.5-4 mm long) are initially topped with a ring of whitish feathery bristles (8-25 mm long).

Common names 
Also known as: bank thistle, bird thistle, black thistle, blue thistle, boar thistle, bull thistle, bur thistle, button thistle, common bull thistle, Fuller's thistle, green thistle, plume thistle, roadside thistle, scotch thistle, spear thistle,
Family 
Asteraceae
Deciduous 
No
Flowering time 
Year round
Native/Exotic 
Exotic
Origin 
Native to Europe, northern Africa (i.e. Algeria, Morocco and Tunisia), western Asia , Pakistan and China.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

A very widely distributed species that is naturalised throughout the southern and eastern parts of Australia. It is very common in south-eastern Queensland, the southern and eastern parts of New South Wales, the ACT, Victoria and Tasmania.

Habitat 

A weed of crops, orchards, vineyards, fallows, pastures, forestry plantations, parks, gardens, roadsides, waste areas, disturbed sites, riparian vegetation, open woodlands and grasslands.

Habit 

A short-lived (i.e. annual or biennial) herbaceous plant usually growing 60 to 120 cm tall, but sometimes reaching up to 2 m in height. This species produces a basal rosette of leaves at first, followed by upright (i.e. erect) and much-branched stems.

Impact and control methods 

"Though this species is primarily a weed of pastures, crops, waste areas and roadsides, it sometimes spreads from these areas into disturbed native grasslands, open woodlands and conservation areas. However, it is not a serious environmental weed in south-eastern Queensland.

Spear thistle (Cirsium vulgare) is regarded as an environmental weed in parts of south-eastern Australia (i.e. Tasmania, Victoria and New South Wales)."

Stem and leaves 

"The stems are ridged lengthwise (i.e. longitudinally) with spiny 'wings' originating where the edges of the leaves continue down the stem. Some plants have hairless (i.e. glabrous) stems while others have a dense covering of woolly white hairs.

Young plants have leaves arranged in a basal rosette. When in the seedling stage of growth, these leaves may have an almost entire margin. However, in older plants these leaves can be up to 45 cm long and 10 cm wide and have a highly divided (i.e. pinnatifid) margin with spines at the tips of the lobes. Stem leaves are alternately arranged and stalkless (i.e. sessile). They are smaller (about 15 cm long and 4 cm wide), also having divided margins, but with the spiny lobes projecting upwards and downwards. These is a particularly large spine (about 15 mm long) at the end of each lobe. Leaf blades have a white woolly under-surface and an upper surface with short, stiff, close-lying hairs giving them a rough (i.e. scabrous) texture."

Flowers and fruits 

"The flower-heads (i.e. capitula) are borne singly or in groups of two or three at the ends of the leafy branches. They are large and showy (3-5 cm across and 3-6 cm long), thistle-like, and without obvious 'petals' (i.e. ray florets). These flower-heads consist of many small, purple or reddish-purple coloured, tubular florets extending outwards from a spiny, broadly egg-shaped (i.e. ovoid) base (i.e. involucre). Flowering occurs throughout most of the year, but is most common from spring through to autumn.

The flattened seeds (2.5-4 mm long and about 1.5 mm wide) are grey or light brown in colour, with darker brown, black or ochre streaks and a deeply sunken apex. They are topped with a ring (i.e. pappus) of whitish feathery bristles (8-25 mm long) that almost surround the seed when it is mature."

Reproduction and dispersal 

"This species reproduces almost entirely by seeds that are equipped with a large 'parachute' of bristles that enhances dispersal by wind.

Seeds are also spread as a contaminant of agricultural produce (e.g. fodder and grain) and to a lesser extent by water, animals, vehicles, machinery and in mud."

Similar species 

"Spear thistle (Cirsium vulgare) is similar to the slender thistles (Carduus pycnocephalus and Carduus tenuiflorus), nodding thistle (Carduus thoemeri). It may also be confused with variegated thistle (Silybum marianum ). These species can be distinguished by the following differences:

■spear thistle (Cirsium vulgare) has green leaves and winged stems. Its broad flower-heads (3-5 cm across) are usually borne singly and have bracts with relatively long greenish-coloured spines.

■slender thistle (Carduus pycnocephalus) has green leaves and winged stems. Its small, slender, flower-heads (about 2 cm long) are stalkless (i.e. sessile) and borne in small clusters (3-4 in number). The uppermost bracts surrounding the flower-heads are shorter than the adjacent florets.

■slender thistle (Carduus tenuiflorus) has green leaves and prominently winged stems. Its small, slender, flower-heads (up to 2 cm long) are stalkless (i.e. sessile) and borne in small clusters (3-8 in number). The uppermost bracts surrounding the flower-heads are longer than the adjacent florets.

■nodding thistle (Carduus thoemeri) has green leaves and wingless stems. Its broad flower-heads (4-8 cm across) are usually borne singly and have purplish coloured bracts. These flower-heads are borne singly and 'nod' or droop distinctively as they mature."