Eucalyptus robusta

Swamp Mahogany, Swamp Messmate

Family: Myrtaceae

A tree to 30 m tall with a broad canopy. 

It is found close to swamps and alongside estuaries in a narrow coastal strip, usually within a few kilometres of the ocean. It grows as far north as Rockhampton, Queensland, south to around Moruya in New South Wales.

It is usually found on sandy and loam soils. It forms a co-dominant part of Swamp Sclerophyll Forests in NSW. 

Bark covers the trunk and branches and is stringy to tessellated, thick red-brown in colour and has a spongy feel. The long branches spread laterally and form a dense canopy.

Eucalyptus spp. have simple and usually alternate adult leaves with juvenile leaves starting off opposite to alternate (disjunct). In this species, juvenile leaves are large, to about 20 cm long and 8 cm wide, ovate to broadly lanceolate, with early leaves in opposite pairs.
Adult leaves are to 16 centimetres long and to 4.5 cm wide, broadly lanceolate to ovate, green and glossy, and with closely spaced “feather-like” side veins running at greater than 45° angle to the main midrib.

The primary inflorescence of “eucalypts” (Angophora / Corymbia / Eucalyptus) is an umbellaster (an umbel-like cluster of flowers). In the flowers of Corymbia and Eucalyptus, the petals and sepals are fused into the distinctive calyptra / operculum (bud cap) which is shed when the flower opens (in some species, 2 bud caps (opercula) are shed). The flowers are conspicuously staminate – where many stamens are basically taking over the role of the petals, all surrounding one central carpel. In this species, flowers are white or cream-coloured and clustered in umbellasters of 7 to 13 flowers. The flowers appear anywhere from March to September, and peak over May and June. The buds measure 2 by 0.8 cm wide and are distinctive in that the operculum / calyptra has a prominent long beak (rostrate), making them spindle-shaped (a useful feature in identification).

The fruit of eucalypts are a woody capsule (commonly called ‘gum nuts’) which come in a wide variety of shapes with the top part having a sunken, flat or raised disc and with the valves inserted, disc-level, exserted to strongly exserted. In this species, the capsules are cylindrical-shaped and very different to any other eucalypt it grows with, to 1.6 cm long to about 1 cm wide (a useful feature in identification). Seeds are light-brown to yellow to 1.8 mm long, pyramidal or obliquely pyramidal in shape.

In the garden

E. robusta adapts well to cultivation, though it often grows too large for home gardens. It can grow very quickly in cultivation and flower profusely.

It will tolerate wet and swampy conditions. It prefers a sandy soil. Will do well in an open area for a shade tree or specimen planting.
A row of E. robusta was planted at the Royal Botanic Gardens, Sydney in 1813, and the trees are still healthy today.

A koala food tree. This species is one of 27 more common eucalypt and corymbia plants eaten by them.

Eucalypts can suffer problems from, caterpillars, leaf eating beetles, psyllids and borers to name a few. In undisturbed conditions, the numbers of eucalypt-feeding insects and their predators and parasites are in balance, so that they rarely cause tree death and most trees quickly recover from attack. In a home situation nature can get out of balance.


Eucalypts can be propagated by seeds which is most common method or grafting.

Cuttings are difficult to start, but can be used in some species. For further information refer to: http://anpsa.org.au/APOL2007/sep07-s1.html

Other information

This species regenerates after fire through the lignotuber as well as epicormic shoots. It can also regenarte via the seed bank. 

Eucalyptus is one of three similar genera that are commonly referred to as “eucalypts”, the others being Corymbia and Angophora.

It is well-known that Eucalyptus is a large and diverse genus. Between 700 and 950 known species are reported, occurring as far north as The Philippines, as well as Indonesia, New Guinea, Timor and Australia. Only 16 species reportedly occur outside Australia. They occur in all Australian states. NSW currently has about 250 species. (See this website for some detailed information: https://apps.lucidcentral.org/euclid/text/intro/learn.htm).

Eucalyptus – from Greek, eu, “well” or “true” and calyptus, referring to the calyptra (καλύπτρo) or operculum, which is a bud cap or covering which covers the developing flowers. The calyptra is a fusion of petals and/or sepals and is shed when the flower opens, leaving a flower with many stamens (staminate) surrounding one female part (carpel).

robusta – Latin – robustus meaning “robust / strong / firm”, referring to the appearance of the trees generally and canopy.

This species is not considered to be at risk of extinction in the wild. 

Field Guide to EucalyptsVol 1 South Eastern Australia M.I.H.Brooker and D.A.Kleining. Blooming Books.

NSW Flora Online (PlantNET) – Eucalyptus robusta profile page

EUCLID – Eucalypts of Australia – Centre for Australian National Biodiversity Research – Eucalyptus robusta profile page                                                                                     https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Eucalyptus~robusta

By Jeff Howes. Editing and additional text by Dan Clarke.