Casuarina glauca 'Cousin It'

Cousin It / Prostrate She-oak

Botanical Name: Casuarina glauca ‘Cousin It’
Family: Casuarinaceae
Origin: Eastern Australia (NSW/QLD coast; horticultural selection)
Plant Type: Evergreen prostrate groundcover (spreading, cascading)

Overview

A distinctive, hair-like weeping groundcover with ultra-fine, bright to mid-green branchlets that flow over edges and down banks. Grown for texture rather than flowers, it’s superb in Adelaide/SA for retaining walls, slopes, rockeries and spill-over edges where it suppresses weeds, shrugs off heat and wind, and handles coastal conditions. Minimal maintenance; just guide or trim where needed.

Key Features

• Mature Size: 0.1–0.25 m H × 1.5–2.5 m W (spread)
• Growth Rate: 30-60 (spread) cm per year under good conditions
• Foliage: Very fine, trailing “needles” (branchlets) forming dense, flowing mats; fresh to mid-green (may bronze slightly in cold/dry spells)
• Flowers: Inconspicuous; grown for foliage (male catkins/female cones rarely noticed)
  
• Seasonal Interest: Evergreen, flowing texture year-round; dramatic cascading effect over edges
• Wildlife Value: Shelter and cover for small lizards/invertebrates; habitat in coastal/native plantings
• Tolerance: Drought-tolerant once established, high heat and wind tolerance; front-line coastal tolerant (salt/spray); light–moderate frost (protect from hard frosts in Hills pockets)
• Planting Density: 2–3 plants per m² (closer for faster cover)
• Pet Friendly: Non-toxic to cats & dogs (ingesting any plant matter may upset tummies)

Where It Works Best

• Sunlight: Full sun to light part shade (densest growth in sun)
• Soil: Free-draining sands to loams and well-drained clay loams; copes with poorer soils; avoid chronic waterlogging (mound/raise on heavy sites)
• Water Needs: Establishment: 2 deep soaks/week for 8–12 weeks. Established: Deep soak every 2–4 weeks in summer (weekly in heatwaves on very sandy/coastal sites); minimal in winter
• Maintenance: Very low. Lightly trim wayward strands after they root into paths/beds; tidy debris from the mat; avoid heavy fertiliser (a light organic feed in spring is ample)
• Lifespan: 10–20+ years in suitable conditions
• Climate Zones: Temperate & Mediterranean SA, including Adelaide Plains, foothills and coastal areas
• Soil pH: Neutral (tolerates slightly acidic–slightly alkaline)

Landscape & Design Ideas

• Coastal banks & retaining walls—cascades beautifully and binds soil
• Rockeries & spill-over edges for striking, low-maintenance texture
• Mass groundcover for hot, exposed Adelaide sites to suppress weeds
• Containers/pedestals where its “green waterfall” effect shines

Why You Will Love It

The ultimate no-fuss, architectural groundcover for Adelaide—handles heat, wind and coastal conditions while delivering that unmistakable, flowing “Cousin It” look with almost zero upkeep.