The leaves are alternate, 4–15 cm long, and pinnate or nearly so, with 7–21 leaflets. The flowers are produced in a tight globose [inflorescence] 1–2 cm in diameter, with no petals. The fruit is also a dense ball of many seeds; in many (but not all) species the seeds bear a barbed arrowhead point, the seedhead forming a burr which attaches itself to animal fur or feathers for dispersal.
Several Acaena species in New Zealand are known by the common name bidibid. The plant is also called the New Zealand burr.