Weird and wonderful members of the plant kingdom - the dangerous, but useful, Eucalyptus

Eucalypts are a species of tree indigenous to Australia. They draw a tremendous amount of water from the soil through the process of transpiration and so one of their uses is as plantation trees where they are planted to lower the water table and reduce soil salination. Eucalypts have also been used as a way of reducing malaria by draining the soil in Algeria, Europe and California. Conversely, on the margins of the Sahara, their incredible height (up to three hundred feet) and fast growth mean that they serve as a wind break and stop the encroachment of sand dunes. This has saved up to 900 miles of agricultural land from being swamped by wind-blown sand

The tree also has medicinal properties - eucalyptus oil is distilled from the leaves and can be used for cleaning, deodorising, and in very small quantities in food supplements; especially sweets, cough drops and decongestants as well as having insect repellent properties. One species of Eucalypt, the ghost gum, has leaves used by Aborigines to catch fish. Soaking the leaves in water releases a mild tranquilliser which stuns fish temporarily, and it also provides the wood for the digeridoo.

However, it's not all good news. Some species of Eucalyptus have a habit of dropping entire branches as they grow and the ground in Eucalyptus forests is covered with dead branches. The Australian Ghost Gum is also known as the widow maker, due to the high number of tree-fellers and lumberjacks who were killed by falling branches and many more people have been killed as they camped underneath the trees. It is thought they shed these large branches to conserve water during periods of drought.

On warm days eucalyptus oil becomes a vapour which rises to give the characteristic blue haze of the Australian landscape. Eucalyptus oil is highly flammable: trees have been known to explode - and bush fires can travel easily through the oil-rich air of the tree crowns. The dead bark and fallen branches are also flammable. Eucalypts are well adapted for periodic fires, in fact most species are dependent on them for spread and regeneration. They do this via lignotubers, reserve buds under the bark and from fire-germinated seeds sprouting in the ashes. It's not such good news for anything in the fire's path though.

Eucalyptus photograph by dan taylor, used under a creative commons attribution licence