Dianella Caerulea 'Cassa Blue'

Cassa Blue Flax Lily /  Cassa Blue

Botanical Name: Dianella caerulea ‘Cassa Blue’
Family: Asphodelaceae
Origin: Australia
Plant Type: Strappy grass-like perennial

Overview

Dianella ‘Cassa Blue’ is a compact, ultra-tidy flax lily for South Australian gardens. It forms dense clumps of powdery blue foliage year-round, then sends up purple-blue starry flowers in spring–summer, followed by decorative deep-blue berries. Ideal for low-maintenance borders, path edges and mass plantings in coastal and Mediterranean climates.

Key Features

• Mature Size: 0.3-0.6 m H x 0.4-0.6 m W
• Growth Rate: 20-30 cm per year under good conditions
• Foliage: Blue-green strappy leaves in very tidy clumps
• Flowers: Purple-blue starry flowers with decorative berries
• Seasonal Interest: Reliable year-round structure; spring–summer flowers and long-lasting berries
• Wildlife Value: Flowers for pollinators; berries for birds; clumps provide habitat
• Tolerance: Drought-tolerant (once established), heat-tolerant, wind-tolerant; coastal-tolerant; clay-tolerant (with improved drainage); light frost (protect from hard frost)
• Planting Density: Mass planting: 2–3 plants per m²; Edges/drifts: 1–2 plants per linear metre
• Pet Friendly: Yes — generally non-toxic to pets (ingesting any plant may cause mild tummy upset)

Where It Works Best

• Sunlight: Full sun to part shade
• Soil: Well-drained loam, sandy loam or improved clay loam (avoid waterlogging)
• Water Needs: Establishment: 2 deep soaks/week for 8–12 weeks. Established: deep soak every 10–14 days in summer; monthly in winter if dry
• Maintenance: Mulch in spring; comb or cut back tired leaves late winter; remove spent flower stems; light feed in early spring
• Lifespan: 15-25 years
• Climate Zones: Suited to temperate and Mediterranean SA gardens, including coastal areas
• Soil pH: Acid, Neutral, Alkaline

Landscape & Design Ideas

• Mass plant for cohesive, low-maintenance ground-level structure
• Edge paths and driveways; great in drifts through gravel gardens
• Feature near entries and outdoor living spaces; suitable for large pots

Why You Will Love It

Fast, reliable and beautifully low-maintenance. ‘Cassa Blue’ delivers crisp blue foliage, seasonal flowers and berries, and excellent drought/heat/coastal resilience — a high-value choice for tidy borders and mass plantings in SA.