Eucalyptus sideroxylon

Red Ironbark, Mugga Ironbark

Family: Myrtaceae

An ironbark eucalypt, potentially reaching 35 m high in the wild.

Eucalyptus sideroxylon is found in Victoria, NSW and Queensland. In NSW, it grows mainly on the tablelands, western slopes and plains, although it also occurs on the fringes of the Sydney basin; as far west as around Cobar and Griffith. It extends into Queensland, through Warwick and Towoomba and up to Gympie. There is a disjunct patch to the south-west of Rolleston which seems to be its northern limit. In Victoria, it occurs mainly in the central areas, in a zone between Albury and Bendigo and a bit further southwards. 

It grows mainly in dry sclerophyll forest and woodland.

The bark is that of an ironbark and very dark in colour.

Eucalyptus spp. have simple and usually alternate adult leaves with juvenile leaves starting off opposite to alternate (disjunct). In this species, juvenile leaves are dull grey-green or glaucous, to 11 cm long and 4 cm wide. Adult leaves are lanceolate, to about 15 cm long, and about 2 cm wide, green to grey-green / blue-green in colour.

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, the umbellasters are 7-flowered, produced in the leaf axils. The buds are diamond-shaped to 1.5 cm long. Flowers can be white, to creamy yellow, to a rich pink or even red, which makes it a very appealing tree.

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 cup-shaped, to about 1 cm wide by long, with a long pedicel usually over 1 cm long (which allows for easy identification within the ironbark group).

In the garden

This species is very hardy, needing less than 400 mm of rain per year to survive, yet can grow in climates with more than 1000 mm of rain per year. It is tolerant of frosts, droughts and poor soil. In cultivation, it will not grow into an overly large tree in most circumstances. 

It is an attractive tree for parks or large gardens, with dark bark, grey leaves and attractive flowers, especially if red. It is reasonably slow growing.

Flowering occurs from April to December and the flowers are white, red, pink or creamy yellow and are attractive to nectar eating birds.

The author has observed that this tree is suited to growing on heavy clay soils and performs well in Sydney’s north.

Street trees can be found through Sydney. It needs some room to spread out but is not an overly large tree.

Anecdotal evidence suggests ironbark-eucalypts drop limbs much less frequently compared to other eucalypts. Can be used to create contrast in a landscaped garden. 


Propagation is from seed which germinates readily. Because of the genetic variation that occurs with seedlings, the red and pink flowered forms cannot be guaranteed to come true to type but usually do.

Other information

The wood is relatively hard and dense, and is often used for firewood. It has very high resistance to rotting and can be used for fence posts, piers, sleepers.

It can regenerate from seed, lignotuber and epicormic buds after fire.

Eucalyptus sideroxylon is one of the best known of the Ironbarks. 

It has become an invasive weed in southern Africa.

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.

sideroxylon – from the Greek sidero (σίδερο) – iron; and xylon (ξύλο) – wood, referring to the very strong wood.

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

NSW Flora Online (PlantNET) – Eucalyptus sideroxylon profile page

Atlas of Living Australia – Eucalyptus sideroxylon profile page

EUCLID – Eucalypts of Australia – Centre for Australian National Biodiversity Research https://apps.lucidcentral.org/euclid/text/entities/eucalyptus_sideroxylon.htm

Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.


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