Westringia hybrid 'Blue Gem'
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Blue Gem Westringia / Coastal Rosemary 'Blue Gem'
Botanical Name: Westringia hybrid 'Blue Gem'
Family: Lamiaceae
Origin: Australia
Plant Type: Evergreen shrub
Overview
A standout coastal shrub for Adelaide and SA, ‘Blue Gem’ brings masses of vivid violet-blue flowers on a dense, naturally rounded plant that laughs off salt, wind and heat. Fine, rosemary-like leaves hold their colour year-round while the bloom peaks in spring and again in autumn, with spot flowers most months.
Key Features
- Mature Size: 1–1.5 m H × 1–1.3 m W (can be kept tighter with light clipping)
- Growth Rate: 30-50 cm per year under good conditions
- Foliage: Narrow, grey-green leaves in whorls; compact, tidy habit
- Flowers: Vivid blue to blue-violet blooms for much of the year (heaviest spring & autumn)
- Seasonal Interest: Evergreen backbone with repeated, high-impact blue flowering
- Wildlife Value: Good for pollinators (native bees & beneficials); dense branching offers shelter for small birds
- Tolerance: Drought & heat tolerant once established; excellent salt & wind tolerance; light frost hardy; suits sandy or limestone soils if well-drained
- Planting Density: Hedge: 1 plant per metre (0.7 m for very tight screens); Specimen/mass: 1.2–1.5 m apart
- Pet Friendly: Generally non-toxic; discourage chewing of any ornamental plant
Where It Works Best
- Sunlight: Full sun to part shade (more sun = tighter form & heavier bloom)
- Soil: Well-drained loam, sandy loam or improved clay; avoid chronic waterlogging
- Water Needs: Establishment: 2 deep soaks/week for 8–12 weeks. Established: deep soak every 10–14 days in summer (more in heatwaves); monthly in winter if dry
- Maintenance: Tip-prune after flowering or light clip 2–4×/yr to keep a crisp outline and encourage new flower spikes; mulch in spring; feed lightly in early spring (native-safe, low-P fertiliser if mixing with natives)
- Lifespan: 15-25+ years
- Climate Zones: Suited to temperate and Mediterranean SA gardens, including coastal areas
- Soil pH: Slightly acidic to alkaline; happy on Adelaide limestone
Landscape & Design Ideas
- Colour-rich hedges and borders that hold a neat line with minimal trimming, delivering true blue flowers that pop against stone, render and timber
- Coastal and poolside planting: thrives in salt spray and wind; pair with lomandra, dianella and olives for a modern Mediterranean palette
- Containers & courtyards: compact habit suits large pots and troughs; place near entries for reliable colour nearly all year
Why You Will Love It
‘Blue Gem’ delivers real blue flowers on a shrub that’s as tough as they come—perfect for Adelaide’s heat, wind and coastal conditions. It stays tidy with a couple of light clips a year, attracts pollinators, and brings months of saturated colour that lifts hedges, borders and pots with virtually no fuss.