Brisbane tree guide

Swamp mahogany

Eucalyptus robusta · also called Swamp messmate

Swamp mahogany is a local gum that grows naturally in swampy coastal ground from southern New South Wales to near Bundaberg. It has thick, spongy red-brown bark, broad glossy leaves and white blossom through the cooler months, and it is a listed koala food tree in South East Queensland. It suits wet, low-lying parts of large properties, but it grows to around 25 metres.

Native to South East Queensland
18 to 25 m tall
Flowers May to October

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Swamp mahogany, from Wikimedia Commons — Photo: Casliber, CC BY-SA 3.0, via Wikimedia Commons

Swamp mahogany at a glance

Height: 18 to 25 m (up to 30 m in the wild)
Leaves: Evergreen
Flowers: White, May to October
Roots: Aggressive
Origin: Coastal NSW from Moruya north to near Bundaberg, including Moreton, Stradbroke and Fraser islands
Family: Myrtaceae

How to identify a swamp mahogany

The bark is the giveaway: thick, soft, spongy and fibrous, reddish-brown to grey-brown, and it covers the trunk and branches. Adult leaves are broad, glossy and dark green, 8 to 17 cm long and paler underneath, with fine side veins at a wide angle to the midrib. Buds sit in groups of about 9 to 15 on a broad, flattened stalk, opening to white flowers. The gumnuts are cylindrical, 1 to 1.6 cm long, with the valves usually joined across the top, a feature EUCLID notes is unique among eastern Australian eucalypts.

Growing a swamp mahogany in Brisbane

Swamp mahogany is a true local, growing wild along the coast from Moruya in New South Wales to near Bundaberg, including Moreton and North Stradbroke islands. In nature it grows in low, swampy sites on sandy soils, which makes it a useful tree for wet or poorly drained parts of larger Brisbane blocks and acreage. Land for Wildlife Queensland lists it as a koala food tree in South East Queensland. It needs plenty of room and is not a tree for a small yard.

What to watch out for

Swamp mahogany becomes a big tree, to about 25 metres and occasionally 30, so plant it well away from the house and boundaries. Unitywater lists large gum trees among the trees not to plant near water and sewer pipes, so keep it clear of pipe runs.

Size. It grows to about 25 metres, and up to 30 metres, so it needs a large block well clear of buildings.

Pruning and care

Once established, swamp mahogany needs little care. Mulch and water young trees through dry spells until they settle in. Formative pruning while the tree is young, keeping one strong leader and removing competing or crossing stems, sets up a sound structure. On older trees, limit pruning to dead, damaged or poorly attached branches. Pruning or removing a tall mature gum near buildings is a job for a professional with the right gear.

Swamp mahogany: your questions

Short answers, from the sources below.

Back to the tree guide

Is swamp mahogany a koala food tree?

Yes. Land for Wildlife Queensland lists swamp mahogany among the koala food trees of South East Queensland, so it is a good choice for koala habitat on larger blocks.

How tall does swamp mahogany grow?

It is usually a medium-sized tree growing to about 25 metres, and EUCLID records trees up to 30 metres tall.

Does swamp mahogany grow in wet soil?

Yes. In the wild it grows in low, swampy sites on sandy coastal soils, so it is one of the gums suited to wet, poorly drained ground.

When does swamp mahogany flower?

Its white blossom appears from late autumn through winter into spring, with flowering recorded from May to October. The species is also used for honey production.

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Sources and credits

Photo: Casliber, CC BY-SA 3.0, via Wikimedia Commons.

This profile updates sheet 46 of the plant profile booklet made for Colourful Tree Lopping in 2013. We checked every fact against current sources and rewrote it for the guide.

Checked October 2026. Weed listings and council rules change: check the council's and the Queensland Government's pages before you act.