Swamp Mahogany

Eucalyptus robusta grows commonly as a straight, upright tree to around 20–30 metres (70–100 ft) tall, with a trunk up to 1 metre (3.3 feet) in diameter at breast height (dbh). The trunk and branches are covered with thick red-brown bark, which has a spongy feel and is stringy—peeling in longitudinal strips. The long irregular branches spread laterally, and form a dense canopy with the broad green leaves. Arranged alternately along the stems, these measure 10–16 centimetres (3.9–6.3 inches) long by 2.7 to 4.5 cm (1.1 to 1.8 in) wide. Adult leaves are 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 white or cream flowers are clustered in inflorescences of from 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 (0.79 by 0.31 in) wide and are distinctive in that the operculum has a prominent long beak, making them fusiform (spindle-shaped). The woody fruits are cylindrical-shaped, 1 to 1.6 cm long by 0.7 to 1.1 cm wide, pedicellate with descending disc and 3 to 4 valves at rim level or slightly exserted. Seeds are light-brown to yellow to 1.8mm long, pyramidal or obliquely pyramidal in shape. The bangalay (E. …

This species occurs in swamps and alongside estuaries in a narrow coastal strip, usually within a few kilometres of the ocean, from Rockhampton, Queensland, south to Jervis Bay, New South Wales. It is also found offshore on Great Keppel, Moreton, Fraser and North and South Stradbroke Islands. It is widely planted as a timber tree, and is considered to be invasive in Hawaiʻi and Réunion, and has become naturalised in Florida. It generally grows on heavy clay soils, but is also found on sandy clay and alluvial sand soils. It grows on sand on offshore islands. Found from sea level to altitudes of 50 m (160 ft) above sea level, it grows in swamps or areas where the water table is high, generally fresh or brackish in nature. Older plants are able to tolerate salt but seedlings cannot. Eucalyptus robusta can also grow in highly acidic sulphate estuarine soils with a pH as low as 2.5. It is a dominant tree in swamp forests, often growing in pure stands or with other trees such as red mahogany (E. resinifera), red bloodwood (Corymbia gummifera), pink bloodwood (Corymbia intermedia), swamp sheoak (Casuarina glauca), snow-in-summer (Melaleuca linariifolia), swamp paperbark (M. ericifolia) and, less commonly, forest red gum (E. tereticornis).

Conservation. …

A long-lived tree, Eucalyptus robusta can live for at least two hundred years. Trees regenerate by regrowing from epicormic buds on the trunk after bushfire. The grey-headed flying fox (Pteropus poliocephalus) eats the flowers, and the koala (Phascalarctos cinereus) eats the leaves. Eucalyptus robusta appears to be one of several key species of eucalypt for the koala in the Shire of Noosa in Queensland. The musk lorikeet feeds on the nectar of the blossoms. It is a favoured tree species of the critically endangered swift parrot on the mainland. It is a keystone species on the New South Wales Central Coast and Illawarra regions, where it is one of few reliable winter-flowering plants. Stands of E. robusta have been drastically reduced by land clearance. Some remnant trees in Robson Park in the Sydney suburb of Haberfield are the last vestiges of the Sydney Coastal Estuary Swamp Forest Complex community in Sydney's inner western suburbs. Insects, such as psyllids and Christmas beetles from the genus Anoplognathus and the eucalyptus chafer (Xylonichus eucalypti) commonly eat the leaves. The rectangular-lerp forming psyllid Glycaspis siliciflava eats only this species. The scale insects Brachyscelis munita and Opisthoscelis pisiformis form galls. …

Eucalyptus robusta adapts well to cultivation, though it often grows too large for home gardens. It has been used as a street tree, and is useful in public areas with wet soils. It can grow very quickly in cultivation and flower profusely. It can flower in its third year of growth in cultivation in optimal conditions, and its timing makes it an important source of food during autumn and winter. Birds are attracted to its flower heads. However, in some years its leaves are infested with lerps and detract from its appearance. A row of E. robusta was planted at the Royal Botanic Gardens, Sydney in 1813, and the trees are still healthy. A cultivar with variegated leaves, E. robusta "Green and Gold" was commercially available in 2005 in Australia. It is smaller than the wild form, reaching 5–8 metres (16–26 ft) in height. Eucalyptus robusta is widely grown from equatorial to temperate regions, tolerating a wide range of climates and conditions. Its fast early growth and tolerance for waterlogging have rendered it a useful tree to grow. …