Bidibidi
Acaena anserinifolia
Acaena anserinifolia , commonly known as bidibid or piripiri, is a distinctive native ground cover renowned for its attractive bronze-tinted foliage and characteristic spiny seed heads. This hardy member of the rose family (Rosaceae) is endemic to New Zealand, found throughout both main islands from coastal to subalpine zones. The species has evolved an ingenious dispersal strategy - its barbed seeds attach to passing animals (and hikers' socks), earning it the Māori name 'piripiri' meaning 'to stick' or 'cling'. Unlike many of its alpine relatives, this adaptable species thrives across a remarkable range of habitats from sea level to 1500 meters elevation. The bronze to purplish-red coloration of its leaves, particularly pronounced in exposed situations, makes it a valuable ornamental for native ground cover plantings where both beauty and durability are required.
Plant Description
Acaena anserinifolia forms dense, spreading mats through a network of creeping stems that root at the nodes. The compound leaves are pinnately divided with 7-13 leaflets, each leaflet 5-15 mm long, oblong to elliptical with serrated margins. The foliage colour varies seasonally and with exposure, ranging from bright green in shaded, moist conditions to deep bronze or purplish-red in full sun and during winter months. This colour change is an adaptive response to UV radiation and cold stress.
The stems are initially prostrate and rooting, then ascending at the tips to 10 cm high when flowering. They are covered in fine, silky hairs, particularly when young. The root system combines fibrous feeding roots near the surface with occasional deeper anchoring roots, allowing the plant to rapidly colonize disturbed ground while maintaining stability on slopes.
Flowering occurs from November to February, though the flowers themselves are inconspicuous. The flower heads are spherical, about 5-8 mm diameter excluding spines, borne on slender stalks 5-15 cm tall. Individual flowers lack petals but have coloured sepals ranging from green to reddish. Following flowering, the distinctive burrs develop - spherical heads 10-15 mm diameter including the barbed spines. Each burr contains numerous achenes, with 4 sharp, barbed calyx spines per achene that efficiently attach to passing animals, facilitating dispersal.
Quick Facts
| Scientific Name | Acaena anserinifolia |
|---|---|
| Height | 5-15 cm |
| Family | Rosaceae (Acaena) |
| Form | Low, creeping groundcover with barbed burrs |
| Light | Full sun to light shade |
| Soil | Freely draining; tolerates poor, sandy or gravelly soils |
| Tolerance | Wind, coastal exposure; occasional light foot traffic |
| Water Needs | Low to moderate |
| Spread | 30-60 cm |
| Frost Tolerance | High - tolerant of severe freezes |
| Salt Tolerance | Moderate to high (coastal species) |
| Growth Rate | Fast |
| Lifespan | Long-lived perennial |
Climate Best Suited to
Widespread in lowland to montane districts. Performs in coastal to inland climates if drainage is good.
Regional Suitability
| City | Climate Suitability |
|---|---|
| Auckland | Ideal |
| Wellington | Ideal |
| Christchurch | Ideal |
| Dunedin | Ideal |
| Queenstown | Ideal |
| Hamilton | Good |
| Tauranga | Good |
| Napier | Good |
| Palmerston North | Good |
| Nelson | Good |
| Invercargill | Good |
| New Plymouth | Good |
| Rotorua | Good |
| Whangarei | Good |
| Whangārei | Suitable |
| Gisborne | Suitable |
| Whanganui | Suitable |
Plant Habitat
Acaena anserinifolia demonstrates remarkable ecological amplitude, thriving from coastal cliffs to subalpine grasslands. It shows particular affinity for open, disturbed, or semi-disturbed habitats including river terraces, track edges, slips, and modified grasslands. The species acts as an early colonizer of bare ground, often among the first plants to establish after disturbance.
In coastal environments, it grows on clifftops and stable dunes, tolerating salt spray and strong winds. These populations often display the most intense bronze coloration, an adaptation to high UV exposure. In montane zones, it occupies forest margins, clearings, and recently disturbed sites along tracks and roads. The species reaches its upper altitudinal limit around 1500 meters, where it grows in subalpine scrub and tussock grassland margins.
Soil preferences are broad, tolerating everything from free-draining gravels to heavy clays, though it performs best in moderately fertile, well-drained soils with pH 5.5-7.5. It shows surprising drought tolerance once established but also withstands periodic waterlogging, explaining its presence in such varied habitats. The species often forms extensive colonies through vegetative spread, particularly on river terraces and coastal slopes where it may dominate the ground layer.
Common associates vary with habitat but frequently include other disturbance-adapted natives like Muehlenbeckia complexa , Raoulia species, Geranium species, and various grasses. In modified environments, it often grows alongside introduced herbs and grasses, competing successfully due to its mat-forming habit and allelopathic properties that may inhibit some competitors.
Plant Conservation
As a widespread and adaptable species, Acaena anserinifolia is not threatened and remains common throughout its range. Indeed, it has proven so successful that it has become naturalized in parts of Australia, California, and Europe, where it is sometimes considered a minor weed. This dispersal success highlights both the effectiveness of its barbed seed dispersal mechanism and its broad ecological tolerance.
Within New Zealand, the species may actually benefit from certain human activities. It readily colonizes disturbed sites along tracks and roads, and its presence in modified grasslands suggests tolerance to moderate grazing pressure. However, in heavily modified agricultural landscapes, it is often replaced by more aggressive exotic ground covers.
The primary conservation value of this species lies in its role in erosion control and as a pioneer plant in restoration projects. Its ability to rapidly cover bare ground while allowing establishment of other natives makes it valuable for stabilizing slopes and revegetating disturbed sites. Additionally, its seeds provide food for native birds, and the dense mats offer habitat for invertebrates and small skinks.
Growing Requirements
Soil
Free-draining soils; tolerates sand, gravel and light clays; avoid waterlogging.
Light
Full sun for dense mats; accepts light shade.
Water
Water to establish; drought-tolerant once rooted.
Planting Guide
Best Planting Practices
Space 30-50 cm apart for coverage. Mulch with gravel to suppress weeds and keep crowns dry. Successful establishment requires careful attention to site preparation, timing, and ongoing care. Consider local climate conditions and soil characteristics when selecting planting locations. Regular monitoring during establishment ensures the best outcomes for long-term plant health and development.
Ecological Role
Environmental Benefits
Acaena anserinifolia functions as both a pioneer species and persistent ground cover in many ecosystems. Its rapid colonization of disturbed ground initiates succession processes, stabilizing soil and facilitating establishment of later successional species. The dense mats effectively suppress exotic weeds while allowing native seedlings to establish through gaps, making it valuable in restoration contexts.
The species supports diverse invertebrate communities. The complex structure of its mats provides habitat for ground-dwelling beetles, spiders, and other arthropods. Several native moth species feed on the foliage, including the endemic Acaena micro-moth ( Coleophora acaenae ). The seeds, despite their defensive spines, are eaten by some birds, particularly finches, which have learned to extract the nutritious achenes.
The barbed burrs play a crucial ecological role beyond simple dispersal. By attaching to animal fur, they not only transport seeds but also create small disturbances where animals scratch or groom, providing ideal establishment sites for the seeds. This co-evolved dispersal mechanism has proven so effective that the plant spreads rapidly along animal trails and through pastoral landscapes.
Research suggests the species may exhibit allelopathic effects, producing chemical compounds that inhibit germination or growth of some competitors. This characteristic, combined with its dense growth habit, allows it to maintain dominance once established and may explain its success in competing with exotic species in modified habitats.
Uses & Management
Garden Uses
Useful as a tough, textural groundcover in dry, sunny spots and coastal gardens.
- Dry borders and banks
- Coastal gardens
- Wildlife and restoration plantings
Management Note
Barbed burrs cling to clothing and pets; avoid near paths if this is a concern.
Landscaping Uses
Garden Design Applications
Excellent for rock gardens, alpine collections, and naturalistic plantings. Best used in open, well-drained positions where its distinctive form can be appreciated. Combines well with other native alpine plants and provides year-round structure. Consider placement carefully due to sharp foliage - avoid high-traffic areas. Creates dramatic focal points in contemporary and native-themed garden designs.
Seasonal Care
Year-Round Maintenance
Spring management focuses on removing winter-damaged foliage and assessing drainage. Summer care emphasizes maintaining adequate moisture without waterlogging. Autumn preparation includes reducing irrigation and ensuring good air circulation. Winter protection may require covering in areas subject to excessive moisture. Year-round monitoring ensures early detection of problems and maintenance of optimal growing conditions.
When to Prune and How Much
Bidibidi ( Acaena anserinifolia ) ( Acaena anserinifolia ) requires minimal pruning to maintain its natural form and health. Focus on removing dead or damaged material and light shaping as needed.
- Remove dead, damaged, or diseased growth at any time of year
- Light pruning after flowering to maintain shape if needed
- Avoid heavy pruning as this may stress the plant
- Use clean, sharp tools to prevent disease transmission
Always prune conservatively, as native plants often have slower recovery rates than exotic species.
How to Grow Bidibidi
From Seed
Growing Acaena anserinifolia from seed is straightforward but requires handling the spiny burrs carefully. Collect entire seed heads when spines are brown and dry (February-April). Wear gloves to avoid the irritating spines. Seeds can be stored dry for up to two years without significant loss of viability.
Remove seeds from burrs by rubbing through a coarse sieve. Sow in spring on standard seed-raising mix, covering lightly with 2-3mm of mix. No pre-treatment is necessary, though soaking for 24 hours may speed germination. Germination occurs within 2-4 weeks at 15-20°C, with rates typically 60-80%. Seedlings develop quickly, ready for pricking out when second true leaves appear.
Pot into individual containers when 2-3cm tall. Growth is rapid - plants may be garden-ready within 3-4 months of sowing. This quick establishment makes seed propagation ideal for large-scale plantings or restoration projects.
From Division
Division is the quickest method for obtaining new plants. Divide established clumps any time from autumn to early spring, though autumn is ideal as it allows establishment before summer dry periods. Lift entire clumps or remove rooted sections from colony edges. Each division needs only a few rooted nodes to establish successfully.
Plant divisions immediately at the same depth as previously grown, spacing 30-50cm apart for ground cover. Water well initially then sparingly until new growth appears. Success rates approach 100% with minimal care.
From Cuttings
Stem cuttings root readily throughout the growing season. Take 5-10cm sections of stem with at least two nodes. Remove lower leaves and insert into free-draining propagation mix. Maintain humidity with mist or cover. Rooting occurs within 2-3 weeks at 15-20°C. This method is particularly useful for propagating selected colour forms or when seed is unavailable.
Advanced Techniques
Advanced propagation techniques include tissue culture for conservation purposes and specialized mycorrhizal inoculation to improve establishment success. Research into optimal hormone treatments and environmental triggers continues to improve propagation rates. Commercial nurseries are developing improved protocols for mass production while maintaining genetic diversity. Understanding these methods helps both commercial growers and dedicated enthusiasts achieve better results with challenging species.
Troubleshooting Common Issues
Poor germination often results from old seed or inadequate stratification. Seedling losses typically indicate overwatering or insufficient drainage. Slow establishment may suggest inappropriate soil conditions or excessive heat stress. Yellowing foliage usually indicates nutrient deficiency or waterlogged conditions. Regular monitoring and prompt intervention prevent minor issues from becoming major problems affecting long-term plant health and garden performance.
Pests & Diseases
Generally pest and disease-free in garden settings, Acaena anserinifolia is remarkably resilient. Its hairy leaves and potentially allelopathic properties may deter many herbivores and pathogens. However, several issues occasionally arise in cultivation.
Powdery mildew can affect plants in humid conditions with poor air circulation, appearing as white powdery coating on leaves. Improve airflow and avoid overhead watering. Severe infections may require removal of affected portions.
Root rot develops in poorly drained soils, particularly in winter. Symptoms include yellowing foliage and stem blackening at soil level. Prevention through proper drainage is essential as affected plants rarely recover. In containers, ensure adequate drainage holes and avoid overwatering.
Spider mites occasionally infest plants during hot, dry periods, causing stippling and bronzing of foliage (beyond the natural coloration). Regular water sprays dislodge mites and maintain humidity levels that discourage infestation.
Slugs and snails may damage new growth, particularly in spring. The mature foliage seems relatively unpalatable, but young shoots are vulnerable. Physical barriers or iron phosphate-based baits provide control where necessary.
Perhaps the main 'problem' in gardens is the plant's vigorous spreading nature and prolific self-seeding. The barbed seeds attach to clothing and pets, spreading the plant to unintended areas. Regular deadheading prevents unwanted spread while maintaining neat appearance.
Cultural Significance
Traditional Uses and Values
Bidibidi (bidibid) holds cultural significance for Māori, who traditionally used various Acaena species for medicinal purposes and as indicators of seasonal changes. The distinctive hooked seeds that attach to clothing and animal fur were observed by early Māori as part of plant dispersal cycles. Today, bidibids represent the interconnectedness of New Zealand's ecosystems and are valued for their role in traditional ecological knowledge. Conservation of these species supports both biodiversity and cultural heritage, particularly in areas where traditional gathering and land management practices continue.
Bonus Tip
Hitchhikers
The "bidibid" is infamous for its seed heads (burrs) which have barbed spines. These hook onto fur, feathers, and hiking socks, which is the plant's clever way of dispersing its seeds over long distances. Keep away from woolly pets!
