cobbler's pegs

Bidens pilosa
habit (Photo: Sheldon Navie)
infestation of young plants (Photo: Sheldon Navie)
older stems (Photo: Sheldon Navie)
oppositely arranged lower leaves (Photo: Sheldon Navie)
close-up of leaf with sharply-toothed margins (Photo: Sheldon Navie)
leaf undersides (Photo: Sheldon Navie)
close-up of immature fruit (Photo: Sheldon Navie)
mature fruit (Photo: Sheldon Navie)
Herb
Opposite
Simple
Yellow
Green

"A short-lived herbaceous plant with upright stems growing up to 1.8 m tall. Its stems are square in cross section and green to purplish in colour. Its paired leaves (2.5-13.5 cm long) have toothed margins and vary in nature depending on their position on the plant. They may be either oval in shape, deeply-lobed or once-compound with 3-7 leaflets. Its small flower-heads (5-15 mm across) have numerous tiny yellow tubular flowers in the centre and sometimes also have some white ‘petals’ 2-8 mm long. Its dark brown or black 'seeds' (4-16 mm long) are elongated in shape and topped with two or three barbed awns (1-4 mm long).

Common names 
Also known as: cobbler's pegs, farmer's friend, beggar's tick, bur marigold, common beggar-ticks,
Family 
Asteraceae
Deciduous 
No
Flowering time 
Year round
Native/Exotic 
Exotic
Origin 
This species is now very widespread throughout the warmer regions of the world, but is thought to have originated in tropical America .
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

A widely naturalised species that is particularly common in the eastern and northern parts of Australia.

Habitat 

This species is a common weed of crops, fallows, orchards, vineyards, waste areas, disturbed sites and populated areas (e.g. gardens, footpaths, parks, etc.). It is also found in re-vegetation areas, forest gaps and margins, open woodlands, urban bushland, riparian vegetation and coastal enviorns.

Habit 

A short-lived (i.e. annual) herbaceous plant with upright (i.e. erect) stems usually growing 0.3-1 m tall, but occasionally reaching up to 1.8 m in height.

Impact and control methods 

"This very common weed grows in a wide variety of habitats. Cobbler's pegs (Bidens pilosa) is well known as a weed of gardens, parks, crops, pastures, roadsides, disturbed sites and waste areas, but it also invades waterways, rainforest margins, open woodlands and coastal sites. For this reason it is also regarded as an environmental weed in New South Wales and Queensland.

Cobbler's pegs (Bidens pilosa) is considered to be among the 200 most invasive plant species in south-eastern Queensland. Dense populations can out-compete native species, and are particularly troublesome in revegetation sites and on the exposed margins of bushland."

Stem and leaves 

"The stems are square in cross section (i.e. quadrangular), mostly hairless (i.e. glabrous) or hairy (i.e. pubescent), and green to purplish in colour.

The paired leaves (2.5-13.5 cm long and 2-11 cm wide) are borne on slightly winged stalks (i.e. petioles) 1-7 cm long, and vary in nature depending on their position on the plant. At the base of the plant the leaves tend to be simple and more or less oval (i.e. elliptic) in shape. Along the stems they are either deeply lobed (i.e. pinnatisect), with three to seven lobes, or once-compound (i.e. pinnate) with 3-7 leaflets that are egg-shaped in outline (i.e. ovate). The uppermost leaves are either simple or have three leaflets, and are usually smaller and narrower (i.e. lanceolate). The leaves, or leaflets, have sharply-toothed (i.e. serrate) margins and pointed tips (i.e. acute apices). Leaves or leaflets also vary somewhat in size depending on their location on the plant (i.e. they are from 1.5-12 cm long and from 0.5-8 cm wide). They are either hairless (i.e. glabrous) or sparsely hairy (i.e. puberulent)."

Flowers and fruits 

"The small flower-heads (i.e. capitula) are borne singly, but are often arranged in loosely branched clusters at the tips of the stems. These flower-heads (5-15 mm across) are borne on stalks (i.e. peduncles) 1-9 cm long have numerous small yellow tubular flowers (i.e. tubular or disc florets) 3-5 mm long in the centre. They sometimes also have one to several white ‘petals’ (i.e. ray florets) 2-8 mm long and are enclosed in two rows of bracts (i.e. involucral bracts). The outer row of bracts (2.7-5 mm long and 0.5-1.2 mm wide) are green with finely hairy (i.e. ciliate) margins, while the inner row of bracts (3-5 mm long and 1-1.8 mm wide) are brownish in colour with pale margins. Flowering occurs throughout most of the year.

The 'seeds' (i.e. achenes or cypselae) are dark brown or black in colour, flattened, and elongated (i.e. linear) in shape. These 'seeds' (4-16 mm long) have a few ridges with tiny hairs (i.e. they are antrorsely hispidulous) and are topped with two or three barbed awns (1-4 mm long)."

Reproduction and dispersal 

This species reproduces only by seed, which readily become attached clothing and animals. The seeds may also be dispersed by vehicles, by water, and in contaminated agricultural produce.

Similar species 

"Cobbler's pegs (Bidens pilosa) is very similar to beggar's-ticks (Bidens alba var. radiata) and greater beggar's-ticks (Bidens subalternans) and bipinnate beggar's-ticks (Bidens bipinnata). These species can be distinguished by the following differences:

■cobbler's pegs (Bidens pilosa) has flower-heads without any 'petals' (i.e. ray florets) or has several small white 'petals' 2-8 mm long. Its leaflets are toothed, but are not usually further divided, and its 'seeds' (i.e. achenes) are topped with two or three upright or spreading (i.e. erect or divergent) awns.

■beggar's-ticks (Bidens alba var. radiata) has flower-heads several relatively large white 'petals' (i.e. ray florets) 10-16 mm long. Its leaflets are toothed, but are not usually further divided, and its 'seeds' (i.e. achenes) are topped with two upright or spreading (i.e. erect or divergent) awns.

■greater beggar's-ticks (Bidens subalternans) has flower-heads with several small yellow 'petals' (i.e. ray florets) or has several small yellow 'petals' 5-6 mm long. Its leaflets are usually further divided (i.e. pinnatifid) and its 'seeds' (i.e. achenes) are topped with two or three upright (i.e. erect) awns.

■bipinnate beggar's-ticks (Bidens bipinnata) has flower-heads without any 'petals' (i.e. ray florets) or has several small yellow 'petals' 1-4.5 mm long. Its leaflets are usually greatly divided (i.e. pinnatifid) and its 'seeds' (i.e. achenes) are topped with two or three spreading (i.e. divergent) awns.
Cobbler's pegs (Bidens pilosa) is also relatively similar to native cobbler's pegs (Glossogyne tenuifolia), which has leaves with several very narrow (i.e. linear) segments and flower-heads with small yellow 'petals' (i.e ray florets) 2-4 mm long."