Acaena novae-zelandiae, commonly known as red bidibid,^[1] bidgee widgee,^[2] buzzy^[3] and piri-piri bur,^[4] is a small herbaceous, prostrate perennial, native to New Zealand, Australia and New Guinea,^[5] of the family Rosaceae.^[1]

Quick Facts Red bidibid, Scientific classification ...

Red bidibid
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Rosales
Family:	Rosaceae
Genus:	Acaena
Species:	A. novae-zelandiae
Binomial name
Acaena novae-zelandiae Kirk

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Acaena novae-zelandiae is a small herbaceous perennial. It is stoloniferous with prostrate stems of 1.5 – 2 mm diameter.^[5] Damage to stolons encourages new shoots to be produced.^[6]

It has imparipinnate leaves, with 9–15 toothed, oblong leaflets, which are approximately 2 –11 cm long.^[5] The adaxial surface of the leaves is dark green and shiny, and the abaxial surface is hairy and glaucous green in colouration.^[2][5][7] The rachis of the leaves is often red.^[5]

The scape is 10 – 15 cm long^[5] and bears a globular, terminal inflorescence, of 20 – 25 mm diameter,^[2] with 70 – 100 flowers.^[5][7] The flowers lack petals and can range in colour from green to white or purple.^[8] The flowers are wind pollinated.^[6]

Each flower produces one achene, bearing four approximately 10 mm long spines,^[2] tipped with barbs,^[2][5][7] which aid dispersal by attaching to wool, feathers and various clothing materials.^[9] When the fruit are ripe, these spines are red in colouration, later becoming brown.

Acaena novae-zelandiae was first formally described in 1871 by Thomas Kirk who published the description in Transactions and Proceedings of the New Zealand Institute.^[10][11] The genus name (Acaena) is derived from the Ancient Greek word akaina meaning "thorn" or "spine",^[12] referring to the spiny calyx of many species of Acaena. The specific epithet (novae-zelandiae) refers to New Zealand.^[1]

Red bidibid is native to New Zealand, Australia and New Guinea. It has also become naturalised in California, Great Britain and Ireland.^[5] It is regarded as invasive in Great Britain where it has established itself in places such as dune habitats on Lindisfarne.^[13][14]

It occurs within a wide range of habitats, including woodlands, shrublands and grasslands, from coastal areas to alpine areas.^[2][7] It grows in freely draining soils such as silty and sandy loams, typically on sites which receive a high amount of sunlight.^[7]

It also establishes readily on disturbed sites such as roadsides.^[9]

Acaena novae-zelandiae may be used for ground cover in gardens or as a lawn substitute. This plant can be prevented from spreading by limiting disturbance to stolons, thus reducing vegetative propagation,^[6] and by mowing flowers before the burrs form.^[15]

It has also been suggested that dried "tiny tips"^[16] of young succulent leaves may be brewed as tea.^{[15][16][17][18]}