Eucalyptus Citriodora (Corymbia Citriodora)
Corymbia citriodora is a tall tree, growing to 35 metres in height (but sometimes taller), from temperate and tropical north eastern Australia. It is also known as lemon-scented gum, blue spotted gum, lemon eucalyptus and eucalyptus citriodora.
Corymbia citriodora has smooth, pale, uniform or slightly mottled bark, white to coppery in summer, and a conspicuously narrow-leaved crown which smells strongly of lemons. Pear-shaped buds are borne in clusters of three, formed in the corner of leaf and stem junctions, whilst fruit (capsules) are urn-shaped. The bark is smooth for the entire height of the tree, often powdery, shedding in thin curling flakes.
It prefers lighter, slightly acidic loamy soils and occurs in dry sclerophyll forest and woodlands in hilly country. Corymbia citriodora has a lignotuber. Flowering has been recorded in January, April, May, June, July, August, October and December.
Plants of C. citriodora are naturalised in the Darling Range near Mundaring, Western Australia and by planting to suburban New South Wales and Victoria.
Kings Park in Perth has a famous, beautiful avenue of this species planted many years ago, but it has spread to become a serious weed there also.
Corymbia citriodora is an important forest tree, in demand for structural timber and for honey production. It also is popular in horticulture both within Australia and overseas. The name Corymbia citriodora comes from the Latin citriodorus, which means lemon-scented.
The essential oil of the lemon-scented gum mainly consists of citronellal (80%), produced largely in Brazil and China. While unrefined oil from the lemon eucalyptus tree is used in perfumery, a refined form of this oil is used in insect repellents. The refined oil's citronellal content is turned into cis- and trans- isomers of p-menthane-3,8-diol (PMD), a process which occurs naturally as the eucalyptus leaves age. This refined oil, which includes related compounds from the essential corymbia citriodora, is known widely by its registered tradename, "Citriodiol", but also by generic names which vary by country or continent: "oil of lemon eucalyptus" or "OLE"(USA); "PMD rich botanic oil" or "PMDRBO"(Europe); "PMD and related oil of lemon eucalyptus compounds" (Canada); Extract of Lemon Eucalyptus (Australia). Pure PMD is synthesized for commercial production from synthetic citronellal.