Bidibidi (Acaena inermis)

Acaena inermis

Not Threatened

Acaena inermis, commonly known as Bidibidi or Purple Bidibidi, is an attractive low-growing native ground cover of New Zealand. With its distinctive purple-bronze foliage and dense mat-forming habit, this versatile plant adds both color and texture to gardens and natural landscapes. Its ecological significance is evident in its role as a native ground cover, helping to prevent soil erosion and providing habitat for small invertebrates. Unlike some other Acaena species, it lacks the barbed burrs that give the genus its common name "bidibid," making it more garden-friendly while still offering important ecological benefits.

Bidibidi (Acaena inermis) showing its distinctive purple-bronze foliage

Image credit: Wikipedia

Quick Facts

Height	5-10 cm
Spread	0.5-1 meter
Water Needs	Low to moderate
Light	Full sun to partial shade
Frost Tolerance	High
Growth Rate	Moderate
Lifespan	Perennial

Climate Best Suited To

Bidibidi is native to New Zealand, where it naturally occurs in open, rocky areas, particularly in montane and subalpine regions. It thrives in cooler climates with moderate rainfall but has proven adaptable to a range of conditions in cultivation. Its natural habitat suggests a preference for good drainage and moderate moisture.

Regional Suitability

City	Climate Suitability
Whangārei	Moderate
Auckland	Moderate
Hamilton	Ideal
Tauranga	Moderate
Rotorua	Ideal
Gisborne	Moderate
New Plymouth	Ideal
Napier	Ideal
Whanganui	Ideal
Palmerston North	Ideal
Wellington	Ideal
Nelson	Ideal
Christchurch	Ideal
Dunedin	Ideal
Invercargill	Ideal

Growing Requirements

Soil Requirements

Bidibidi adapts to various soil conditions but performs best in:

Well-draining soil
Sandy or loamy textures
pH range from slightly acidic to neutral (5.5-7.0)
Low to moderate fertility
Can tolerate poor soils if drainage is good
Soil type affects its ecological significance in different habitats

Light Requirements

This ground cover is versatile regarding light conditions:

Full sun to partial shade
Best foliage color in full sun
More open growth in shadier positions
Tolerates dappled light under trees
May need afternoon shade in hotter regions
Ideal position varies by regional climate

Water Requirements

Bidibidi has low to moderate water needs:

Water regularly until established
Once established, moderate drought tolerance
Prefers consistent moisture but not wet soil
Water deeply but infrequently
Reduce watering in winter
Mulch to retain soil moisture

Uses & Significance

Garden Uses

Coastal gardens
Ground covers
Rock gardens
Between pavers
Container plantings

Ecological Value

Dune stabilization
Bird food source
Coastal habitat
Soil erosion prevention
Habitat for small invertebrates
Natural ground cover in native ecosystems
Part of New Zealand's biodiversity

Seasonal Care Calendar

Spring

Remove any winter-damaged foliage
Apply a light application of slow-release fertilizer if needed
Divide overgrown clumps if necessary
Plant new specimens as soil warms
Monitor for early-season pests
Trim back any unwanted spread

Summer

Water during extended dry periods
Monitor spread and trim if needed
Remove weeds that may compete
Watch for signs of heat stress

Autumn

Ideal time for planting or dividing
Reduce watering as temperatures cool
Clean up any dead foliage
Apply mulch for winter protection

Winter

Minimal care needed
Check for frost damage
Avoid walking on plants when frozen
Plan for spring division if needed

When to Prune and How Much

Bidibidi generally requires minimal pruning:

Trim back overgrown areas in spring or autumn
Remove dead or damaged foliage as needed
Control spread by cutting back edges of the mat
Light pruning encourages denser growth
No hard pruning required

Planting Guide

When to Plant

Best planted in autumn or spring when temperatures are mild and rainfall is more reliable. This gives plants time to establish before extreme weather conditions.

Site Preparation

Choose a site with good drainage and appropriate light conditions. Clear the area of weeds and loosen the soil to a depth of 15-20 cm. If soil is heavy, incorporate sand or fine gravel to improve drainage.

Spacing

Space plants 30-40 cm apart for ground cover use. They will spread to form a continuous mat over time. For faster coverage, plant more densely at 20-25 cm spacing.

Planting Depth

Plant at the same depth as the nursery container. Create a small basin around each plant to collect water during establishment.

Initial Care

Water thoroughly after planting. Apply a thin layer of fine mulch around but not touching the crown of the plants. Keep soil consistently moist until plants show signs of new growth.

Propagation

Division

Difficulty: Easy

The most reliable method:

Best done in autumn or early spring
Dig up established clumps
Gently separate into smaller sections
Ensure each division has roots and several growing points
Replant immediately at the same depth as before
Water thoroughly after planting
Keep soil consistently moist until new growth appears

Cuttings

Difficulty: Moderate

For creating multiple plants:

Take 5-10 cm stem cuttings in spring or autumn
Remove lower leaves
Dip cut end in rooting hormone (optional but helpful)
Insert into a mix of sand and peat or quality potting mix
Keep consistently moist but not wet
Place in bright, indirect light
Roots should develop within 4-6 weeks
Transplant when well-rooted

Seeds

Difficulty: Moderate to Difficult

For larger quantities:

Collect seeds when ripe
Clean seeds by removing any pulp or debris
Sow fresh seeds in autumn or stratify for spring sowing
Use a well-draining seed-raising mix
Cover seeds lightly with fine grit or sand
Keep consistently moist but not wet
Germination can be slow and irregular
Transplant seedlings when they have several true leaves

Cultural History

Bidibidi has a place in New Zealand's natural and cultural heritage:

Traditional Māori Uses

Various Acaena species were known collectively as "piripiri" or "hutiwai" in te reo Māori
Unlike some other Acaena species with barbed burrs used for medicinal purposes, A. inermis lacks these burrs
Limited documented traditional uses compared to other Acaena species
Recognized as part of the natural landscape

Ecological Significance

Natural component of open, rocky habitats
Provides ground cover that prevents soil erosion
Creates habitat for small invertebrates
Contributes to biodiversity in montane ecosystems
Adapted to survive in challenging environments

European Settlement Impact

Documented by early European botanists
Habitat reduced through land development
Recognized for its ornamental potential
Cultivated varieties developed for garden use

Contemporary Significance

Today, Bidibidi is valued both for its ecological role in native ecosystems and as an ornamental plant in gardens. Its attractive purple foliage and low-maintenance nature make it popular for rock gardens, borders, and as a lawn alternative. Several cultivars have been developed, including 'Purpurea' with enhanced purple coloration. Conservation efforts include preserving its natural habitat and using it in restoration projects.

Pests & Diseases

Common Pests

Slugs and Snails: May damage new growth. Control with organic baits or barriers.
Aphids: Occasionally infest new growth. Wash off with water spray or treat with insecticidal soap.
Scale Insects: May appear on stems. Control with horticultural oil or insecticidal soap.

Common Diseases

Root Rot: Caused by overwatering or poor drainage. Ensure well-draining soil and avoid waterlogged conditions.
Powdery Mildew: May appear in humid conditions with poor air circulation. Improve spacing and air flow.
Leaf Spot: Various fungi can cause spotting on leaves. Remove affected foliage and improve air circulation.

Environmental Issues

Heat Stress: In very hot conditions, foliage may brown at edges. Provide afternoon shade in hot regions.
Waterlogging: Cannot withstand constantly wet soil. Ensure good drainage.
Competition: May be outcompeted by more aggressive plants. Control surrounding vegetation until established.

Bidibidi is generally resilient to pests and diseases when grown in appropriate conditions. Its natural adaptations to challenging environments make it relatively trouble-free. Most issues can be prevented by providing good drainage and appropriate light levels.

Bonus Tip

Create a stunning color contrast by pairing Purple Bidibidi with silver-foliaged native plants like Silver Sheep's Mat or Leptinella squalida 'Platt's Black' (Black Brass Buttons). The combination of purple and silver creates a sophisticated, contemporary look that's particularly effective in modern garden designs. This pairing works beautifully in rock gardens, along pathways, or in container plantings. Both plants share similar growing requirements, making them compatible companions that will thrive together while creating year-round visual interest even when not in flower.