Botany

Trees of Australia the Sandalwood Tree



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Sandalwood is an aromatic tree with the scientific name of Santalum spicatum. It is one of a small number of species which occur in Australia but the family Santalaceae extends beyond that continent. Another quite well-known member of the family is Santalum acuminatum or quandong (also known as native peach).

There are around 15 different species of sandalwood growing throughout the world but only two main varieties. The Australian sandalwood (Santalum spicatum) and Indian sandalwood (Santalum album) are, or were, traded internationally. India now supplies only enough for its domestic needs. Western Australia now supplies about 60% of the world’s sandalwood.

The sandalwood is endemic to semi-arid regions on the edges of southern Western Australia. It is a shrubby to small tree with grey-green foliage. It is tolerant of drought and salt and may grow to six metres. Sandalwood trees flower from January to April. The flowers are very small but the nectar attracts flies, bees, ants and wasps. Single fruits mature from the flowers from August to December. A smooth, spherical orange fruit develops into a hard nut of 15 to25mm diameter. The white kernel is edible.

The heartwood of the sandalwood produces an essential oil which is used in cosmetics, soaps, and medicines. The oils have unique ‘fixing’ qualities which are utilised in shampoos, lotions, bath oils and other preparations. Fixatives, either natural or synthetic, are used to reduce evaporation and to improve stability. This results in a product which lasts longer whilst retaining its original fragrance. Its subtle fragrance of the sandalwood imbues perfumes such as ‘Obsession’ by Calvin Klein and ‘Opium’ by Yves St. Laurent.

The particular trait of this genus is that its members are all root hemi-parasites. These plants attach their roots to the roots of other plants. They then use the connection (or haustoria) to gain some of their nutrient and water requirements from the host species. This symbiotic relationship lasts throughout the life of the sandalwood tree.

At one time, trade in sandalwood was the primary export earner for Western Australia, provided over half of its revenue. It has been exported from WA since the 1840s. Over 300,000 tons of sandalwood were exported by 1920. Much of this export was for the production of joss sticks. The pungent sandalwood has an important religious significance in the Hindu and Buddhist religions.

Although once widespread throughout the southern part of the state, natural stands of sandalwood are now rare. Indiscriminate harvesting of the trees, and clearing of vast areas for agriculture finally resulted in controls being introduced to prevent the total extinction of the tree.

Plantations of Australian sandalwood are now quite common through the wheatbelt area of Western Australia with Indian sandalwood being grown in the Ord River irrigation area in the far north of the state. The plantations are a viable way for farmers to diversify, and has particular benefit in areas where soil salinity is an ever-increasing problem.

The best host trees appear to be nitrogen-fixing plants such as the acacias (wattles) which are native to Australia. Acacia acuminata or jam-tree is often used as a host tree. The jam tree grows on a variety of soil types and can sustain its symbiotic relationship with the sandalwood for 15 to 30 years. The jam tree itself is variable and it is important to choose a variety suited to the area in which it is to be planted. Other species sometimes used with the jam are the rock she-oak (Allocasuarina huegeliana), mulga (Acacia aneura) and wodjil (Acacia resinimarginea).

At around five years of age, the heartwood will start to form. Oil is extracted from the heartwood. The older the tree, the more heartwood and hence more oil. Generally, Australian sandalwood plantations are harvested when the trees are between 12 and 20 years old. The nut or seed contains very high levels of protein and are sold as a food product.

Sandalwood oil also has many medicinal qualities which are exploited to treat herpes, thrush, acne, tinea, psoriasis, joint pain and sunburn as well as other conditions. Its anti-inflammatory and antibacterial properties are being increasingly recognised. The Institute of Pharmaceutical Chemistry in Vienna has produced findings stating that massage oil manufactured from sandalwood is useful in the treatment of hypertension and blood pressure problems.

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