Cobblers Pegs is 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).