CDFA Plant Health

Noxious Weed Photographic Gallery

Biddy-biddy [Acaena novae-zelandiae Kirk][CDFA List: A] Photographs Map of Distribution

Pale biddy-biddy [Acaena pallida (Kirk) J.W. Dawson][CDFA list:A] (see Similar Species)

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SYNONYMS: Bidibid; bidgee-widgee; piripiri

GENERAL DESCRIPTION: Noxious herbaceous perennial, with woody stolons that root at the nodes and bur-like seed heads. Stems are prostrate to erect depending on environmental conditions. Typically, plants grow clustered together forming large mats where individual plants are indistinguishable. Introduced from New Zealand. Numerous species and varieties or hybrid populations of Acaena are described in New Zealand, and opinions differ as to their distinction. In California, Acaena anserinifolia (Forster & Forster f.) Druce (common name also biddy-biddy) and pale biddy-biddy [A. pallida (Kirk) Allan] are cultivated as ornamentals. Pale biddy-biddy may be naturalized as a weed to an uncertain extent, but A. anserinifolia has not escaped cultivation. Populations of biddy-biddy were previously misidentified as A. anserinifolia.

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SEEDLINGS: Cotyledons spatulate, stalked. First 1-several leaves to 2 cm long, including the petiole, with 3 coarse-toothed, ovate leaflets. Subsequent leaves with a gradual increase in leaflet number, from 5 to 11. Seedlings are killed by anaerobic conditions in water saturated soils.

MATURE PLANT: Stipules leaf-like, 1-1.5 cm long, fused to the petioles, and sometimes lobed at the tip. Leaves alternate, once pinnately compound, typically 2-6 cm long. Leaflets 7-11, elliptic to oblanceolate, 5-15 mm long. Leaflet margins curl downwards and are evenly toothed to less than ¼ the distance to the midvein. Upper surfaces of leaflets shiny, glabrous or sparsely hairy. Lower surfaces paler, sparsely to densely hairy on the veins and margins. Stems 1-2 mm diameter.

ROOTS and UNDERGROUND STRUCTURES: Rhizomes and stolons woody, to 1.5 m long. Adventitious roots form at lower nodes and penetrate the soil to 3-5 cm.

FLOWERS: Spring (May-July). Flowering heads terminal on 10-20 cm long stems produced from 2-year-old branches. Heads spheric, about 1 cm diameter (3-3.5 cm in fruit), and composed of 80-100 (120) flowers. Protruding white stamens and stigmas are the most observable feature of the flower heads. Flowers have a hypanthium (flower tube) 2-5 mm long and lack petals. Sepals 4, elliptic-ovate, about 1.5 mm long. Stamens 2, white. Style 1 with a plumose white or purple-tinged stigma. Barbed spines on the hypanthium elongate after fertilization. Ovary superior, matures before stamens. Flowers in a head mature sequentially from the base to the apex. Wind-pollinated.

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FRUITS and SEEDS: Consists of 1 (rarely 2) elliptic achene surrounded by a dry, hardened, unangled hypanthium. Hypanthium body obconical, 2.5-4 mm long, covered with hairs, and with 4 spines 10-15 mm long extending from the slightly contracted top. Spines are red when fruits are immature and have short, backwards pointing barbs at their tips. At maturity fruiting heads form round burs, 3-3.5 cm diameter, that disperse as units. Most fruits are not dispersed beyond the vicinity of the parent plant, and a mat of lodged fruits can develop in the existing vegetation. Clinging burrs have the potential to be transported great distances.

POSTSENESCENCE CHARACTERISTICS:Overwintering leaves die shortly after new shoots begin to develop. Petiole bases of dead leaves persist for at least 3 years.

HABITAT: Open, disturbed, well-drained sites, including stable dunes, open scrub, grassy areas, and trampled sites in coastal habitats where some summer moisture is available and frosts are infrequent. Plants thrive on poor soils and compete poorly with established vegetation.

DISTRIBUTION: Uncommon. North Coast (Humboldt, Sonoma Cos.), Central Coast (Marin, Contra Costa, Alameda, Santa Cruz, Monterey Cos.), and northern South Coast (Santa Barbara Co.). To 200 m (650 ft).

PROPAGATION/PHENOLOGY: Reproduces by seed and vegetatively from stolons. Most seed heads fall near the parent plant, but some may disperse to greater distances with human activities and by clinging to shoes, clothing, and the feet, fur, or feathers of animals. Plants produce large numbers of seed. One large plant can produce hundreds of seed heads with ~70-100 seeds per head. Seed heads can be highly viable (>90%). Under experimental conditions mosts seeds germinate between 5-20º C (41-68º F), optimal ~15 ºC (59º F), and light appears to be required. Seed harvested from immature green burrs does not germinate or mature. Mature shoots can produce 20-30 nodes per season, with each node (including buried nodes) producing a new shoot the following season.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL: Mechanical damage of mature plants encourages stolons to produce new shoots. Flower heads cut before fruits mature do not produce viable seed.

SIMILAR SPECIES: Unlike biddy-biddy, A. anserinifolia has leaflet upper surfaces that are dull and sparsely to densely covered with silky hairs, about 50-60 flowers per head, fruiting heads 1-2 cm diameter, and fruit spines 4-9 mm long that are rose or yellow-green on immature fruits. Stems are 1-1.5 mm diameter. Pale biddy-biddy is very similar to biddy-biddy, but has leaflets 1-3 cm long with a shiny, slightly wrinkled appearance, fruit spines 10-20 mm long, and hypanthium bodies in fruit 4-6 mm long, often with stunted prickles on the sides. Typically stems are 2-3 mm diameter.

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Biddy biddy is an herbaceous perennial Native to New Zealand. It is believed that A.Novae-zelandiae spread from New Zealand to other countries in imported shipments of wool. Seed dispersal by burrs clinging to wool or fur is the primary mechanism of spread. In studies from Venezuela on a similar burr forming species, (Acaena elongata L.), high correlations between cattle movements and plant densities were observed. Grazing animals such as cattle and sheep should be restricted from patches after seed set. In its native habitat, this plant is a poor competitor and is generally only a problem in nutrient poor pastures where overgrazing has occurred. Fertilizer applications at recommended rates for pastures and improved grazing management should prevent its spread. Mechanical control by tillage may result in increased vegetative reproduction and is not recommended. There has been very little information published on the use of herbicides for controlling this plant, likely due to a lack of economic importance.

There are no currently registered biocontrols for A. Novae-zelandiae. A biocontrol program was established in the late 1920's in New Zealand. A sawfly, Antholcus varinervis (Spin.), now Ucona acaenae, which attacks the foliage and developing flowers of A. anserinifolia was identified and established at a few locations in New Zealand in 1936. No updates have been published on the success of this program.

In California, A. anserinifolia and A. pallida are sold as ornamentals. Native ornamental replacements for these species would be Potentilla spp., Heuchera spp., and Achillea millefolium L. Contact your local plant nursery for the availability of these natives.

Gynn, E.G. and A.J. Richards. 1985. Biological Flora of the British Isles: Acaena novae-zelandiae T. Kirk. Journal of Ecology. 73:1055-1063.
Laing, R.M. and E.W. Blackwell. 1964. Plants of New Zealand. Seventh ed. Whitcombe and Tombs Ltd., Christchurch, London, Sydney. 210-212.
Martin, W. 1961. The Flora of New Zealand. Fourth ed. Whitcombe and Tombs Ltd., Christchurch, London, Sydney. 290-292.
Salmon, J.T. 1968. Field Guide to the Alpine Plants of New Zealand. A.H. & A.W. Reed, Wellington, Auckland, Sydney. 84, 315.
Webb, Colin, Peter Johnson, and Bill Sykes. 1990. Flowering Plants of New Zealand. D.S.I.R. Botany, Christchurch, New Zealand. 92.
Webb, C.J., W.R. Sykes, and P.J. Garnock-Jones. 1988. Flora of New Zealand: Volume IV: Naturalised Pteridophytes, Gymnosperms,
Dicotyledons. Botany Division, D.S.I.R., Christchurch, New Zealand. 1053-1063.

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