Melastoma malabathricum
shrub

Blue Tongue

Melastoma malabathricum

The Story

Plant Bio

Melastoma malabathricum, commonly known as blue tongue, is an upright evergreen shrub native to the wet sclerophyll forests and swamp margins of tropical and eastern Australia. The species is distinguished by its opposite, ovate leaves featuring three prominent longitudinal veins and a rough texture of stiff, short hairs.

During spring and summer, the branchlets produce terminal clusters of purple to mauve flowers with distinctive curved, unequal stamens. These blooms are followed by soft, pulpy blue-black berries that stain the mouth blue and attract fruit-eating native birds.

Uses & Benefits:

Ornamental UsesProvides purple-to-mauve floral displays over spring and summer, complemented by attractive, deeply veined evergreen foliage.
Practical UsesExcellent for stabilizing wet soils, rain gardens, and swamp margins where other shrubs might fail due to periodic waterlogging.
Ecological BenefitsAttracts native bees and generalist insect pollinators, while the sweet blue-black berries provide food for native fruit-eating birds.

Essentials

At a Glance

Plant Type

Shrub

Height

79 inches

Width

59 inches

Light

Full Sun, Partial Sun

Zones

9, 10

Water

High

Humidity

High

Lifespan

Moderate

Native To

Tropical and eastern Australia

Toxicity

Non-toxic

Bloom period

Spring – Summer

J
F
M
A
M
J
J
A
S
O
N
D

In flower about 4 months of the year

Planting

How to Grow

  1. Select a planting site in full sun to partial shade with acidic, moist soil.
  2. Dig a hole twice the width of the root ball and incorporate organic matter to help retain moisture.
  3. Plant at the same depth as the nursery pot, backfill, and water thoroughly to settle the soil.
  4. Apply a thick layer of organic mulch around the base, keeping it clear of the main stem.
  5. Water regularly to ensure the soil remains consistently moist, especially during dry spells.

Pro Tip

Never prune hard into old, leafless wood as this species lacks the regenerative capacity of exotic Tibouchina; instead, perform light tip-pruning immediately after flowering to maintain a dense, bushy habit.

Keep It Thriving

Care Guide

Do

  • Keep the soil consistently moist.
  • Apply organic mulch to retain root moisture.
  • Tip-prune after flowering to maintain a bushy shape.
  • Protect young plants from heavy frost.

Don't

  • Do not prune hard into old, bare wood.
  • Do not allow the soil to dry out completely.
  • Do not apply high-phosphorus fertilisers.
  • Do not plant in highly alkaline soils.

Seasonal Care Calendar

TaskJanFebMarAprMayJunJulAugSepOctNovDec
Fertilize
Mulch
Pest Check
Prune
Winter Prep

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Wet-zone plantingsSwamp marginsRain gardensUnderstory screeningCoastal heath gardens

Companion Plants

Gahnia sieberiana Leptospermum juniperinumBlechnum nudumBanksia robur

Multiply

Propagation Methods

Good to Know

Common Questions

Blue Tongue questions

What zones can Blue Tongue grow in?

Blue Tongue is hardy in USDA Zones 9–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

When does Blue Tongue bloom?

Blue Tongue typically blooms in spring through summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Blue Tongue need full sun?

Blue Tongue does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.

Keep exploring

Explore the genus

Hardy in your zone?

Grow Blue Tongue with confidence

See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.

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