River Red Gum
River Red Gum

The River Red Gum (Eucalyptus camaldulensis) is a tree of the genus Eucalyptus. It is one of around 800 in the genus. It is a plantation species in many parts of the world, but is native to Australia, where it is widespread, especially beside inland water courses. Oddly, it is named for a private estate garden near the Camaldoli monastery near Naples (L'Hortus Camaldulensis di Napoli), from where the first specimen came to be described. Material from this tree was used by Frederick Dehnhardt, Chief Gardener at the Botanic Gardens in Naples, to describe this species in 1832.

It is a familiar and iconic tree seen along many watercourses right across inland Australia. The tree produces welcome shade in the extreme temperatures of central Australia, and plays an important role in stabilising river banks.

The tree can grow to 45 metres (148 ft) tall; it has smooth bark, ranging in colour from white and grey to red-brown, which is shed in long ribbons. The tree has a large, dense crown of leaves. The base of the bole can be covered with rough, reddish-brown bark. The juvenile and adult leaves are stalked, with the adult leaves broad at the base, tapering to the tip. The adult leaf colour is a dull blue-green. The leaf also contains several to many oil-producing glands in the un-veined areas of the leaf. It is fast growing, and usually grows to 40 to 45 metres (130 to 148 ft) in height, depending on its location. The tree grows straight under favourable conditions, but can develop twisted branches in drier conditions.

River Reds and many other eucalypts have an ominous nickname, "Widow Maker", as they have a habit of dropping large boughs (often half the diameter of the trunk) without warning. This form of self-pruning may be a means of saving water or simply a result of their brittle wood. This is also an efficient way of attracting wildlife that live in the holes formed.

The species can be found along the banks of watercourses, as well as the floodplains of those watercourses. Due to the proximity to these watercourses, River Red Gum is subject to regular flooding in its natural habitat. River Red Gum prefers soils with clay content. The trees not only rely on rainfall but also on regular flooding, since flooding recharges the sub-soil with water.

The association of the River Red Gum with water makes the tree a natural habitat choice, indeed sometimes the only choice in drier areas, for other species. The trees provide a breeding habitat for fish during the flooding season, which also benefits aquatic bird life that depend on fish as a food source during their own breeding season. The "snags" formed when River Red Gums fall into rivers such as the Glenelg, are an important part of river ecosystems, and vital habitat and breeding sites for native fish like River Blackfish. Unfortunately most snags have been removed from these rivers, beginning in the 1850s, due to river-improvement strategies designed to prevent hazards to navigation, reduce damage to in-stream structures, rejuvenate or scour channels, and increase hydraulic capacity to reduce flooding. However, the Murray–Darling Basin Commission has recognised the importance of snags as aquatic habitat, and a moratorium on their removal from the Murray River has been recommended.

Hollows start to form at around 120–180 years of age, creating habitat for many wildlife species, including a range of breeding and roosting animals such as bats, carpet pythons, and birds. The dense foliage of the tree also provides shade and shelter from the sun in drier areas. The Superb Parrot, a threatened species, is amongst the bird species that nest in the River Red Gum.

River Red Gums contribute to the provision of nutrients and energy for other species through leaf and insect fall. This is especially important to the ecology in areas of low nutrients. The tree's preferred habitat of floodplains and watercourses also gives it the role of flood mitigator, which slows silt runoff.