Casuarina glauca 'Cousin It'
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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)
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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.