Sandalwood is a precious tree with a highly aromatic wood. Because of its economical and cultural uses it is very important to many countries around the Pacific and Eastern Indian Ocean regions where it grows or is traded. The wood is prized for making furniture, ornaments, sacred objects, carvings and joss sticks (incense). The essential oil is used in medicine, perfume and aromatherapy.

Botany/Origins

There are 16 species of sandalwood (Santalum) that grow naturally throughout the Pacific and Eastern Indian Ocean regions. Sandalwoods are evergreens ranging in size from tall shrubs up to large trees. They grow in a variety of climates--from the Australian desert to subtropical New Caledonia--and at elevations from sea level to over 8000 feet. Sandalwood is a parasitic plant, equipped with special structures on its roots that penetrate the roots of host plants and obtain nutrients.

The most well-known and economically important species is Santalum album, or Indian sandalwood. Indian sandalwood has the highest oil content (6 to 7%) and a desirable aroma profile. New Caledonia's S. austrocaledonicum and Fiji's S. Yasi are also distilled to produce essential oil. S. spicatum from Australia has been valued for its wood for many years, and has recently also become a source for essential oil. Many of the other species are used for their wood, for building, firewood and for furniture making.

Trees harvested for oil are selected by age and size because of the higher proportion of heartwood (and thus essential oil) in larger trees. Dead-standing or fallen trees are also harvested because the wood holds onto the essential oil for many years. The whole tree is harvested and used--including the sawdust and the stump (which has the highest oil content) and the sapwood (which contains a small amount of oil). The lower grades of sandalwood, such as the sapwood, are used for incense and for chips and powder, while the better logs are used in carving (from small objects to furniture).

Types of Sandlewoods

Santalum album, Indian 

The fragrance of sandalwood is interwoven with Indian history and culture. The first mention of it in Indian literature is found around 2000 B.C. in the Ramayana. It was included with spices and silk among the first trade items with Middle Eastern and other countries. In 1792 sandalwood was declared a "royal tree" by the Sultan of Mysore--a status that continues today with the Indian government "owning" all the sandalwood trees. (Individuals can get up to 75% of the value of trees growing on their land in payment for growing and protecting the trees--but their harvest must be approved by the government.)

Indian sandalwood's many uses include medicine, incense, burning of chips for ritual use, perfumes and beauty care products, and for carving religious and other artifacts.

Most Indian sandalwood grows on the Deccan Plateau in southern India, with the majority of the trees in the states of Karnataka and Tamil Nadu. Santalum albumis found in dry, deciduous forests. It is considered a slow-growing tree and is easily damaged by fire, various pests, grazing pressures and disease.

The amount of heartwood in a tree varies considerably depending on age, soil and climate conditions--and other factors not entirely understood. The essential oil found in the heartwood of the trees does not even start to form until the trees are at least 10 years old, and trees are not usually harvested until they are at least 30 years old. The heart is yellowish to dark brown, with the lighter-colored wood containing higher levels and a better quality of essential oil than the darker wood. Oil content is also highest in the root and decreases as one moves up the tree. The highest concentrations of essential oil are found at the core of the heartwood, with decreasing amounts as one moves out from the center.

Sandalwood essential oil is mostly obtained by steam distillation (the practice of water distillation is considered outdated). It is colorless to pale yellow and somewhat viscous. The top note (the first aroma you smell) is very soft with a sweet-woody, balsamic body note and a long-lasting bottom note (which is why sandalwood is such a good fixative).

Santalum spicatum, Australian Sandalwood

While Australia has five native species of sandalwood, only two are considered commercially important, S. spicatum and S. lanceolatum. The wood of both species was exported starting in the early 1800s, much of it to China. As demand grew and supplies of other sandalwoods dwindled, more and more trees were cut for export. The government in Australia first attempted to control the harvest of trees with the Western Australian Sandalwood Control Act of 1929. Also around this time, essential oil production from S. spicatum was systemized enough to control the quality so that it was considered therapeutically equivalent to East Indian oil. In 1932 S. spicatum was added to the British Pharmacopoeia.

S. spicatum or Western Australian sandalwood was originally found across a large area of Western Australia from the arid interior to the woodlands. It is a small tree that grows to 20 feet tall. Australian sandalwood begins to bear fruit at 5 to 10 years of age, with flowering beginning in March or April. Trees mature much faster where there are higher levels of moisture (30 years to maturity) than in the dry regions (where trees may take 50 or more years to mature). Early over-harvesting and the conversion of forest to farmland in the regions with higher rainfall has eliminated most of the sandalwood trees in the area. Much of the replanting being done is in this region (the wheat belt) where the higher rainfall provides a better chance of success. Control of the sandalwood harvest and encouragement of plantation planting by the Western Australia government are being used to ensure a sustainable supply of Australian sandalwood.

The steam-distilled Australian sandalwood essential oil has chemical components similar to Indian sandalwood, but there are differences in levels of those constituents and in their respective aroma profiles. The most significant difference in make-up is that Indian sandalwood has much higher levels of santalol (25 to 30% versus 60 to 70%). The difference in the aroma of the two oils is most pronounced in the top note. Australian sandalwood has a more resinous, drier and less sweet top note than Indian sandalwood. The aroma of the two oils becomes more alike in the middle notes--and the all-important base notes are almost identical. In aromatherapy, Australian steam distilled sandalwood essential oil can be used the same as Indian sandalwood.

There are two types of Australian sandalwood oil being sold, one a true steam distilled essential oil and another that is solvent extracted or co-distilled oil. The co-distilled oil is produced by extracting ground sandalwood with hexane to create an oleoresin. The separation of the oil from the oleoresin ocurs during co-distilling under vacuum with a co-distilling agent and finally it is rectified. Steam distilled oil is produced using only heat and produces a oil that is more complex and characteristic of sandalwood. Aura Cacia sells only true steam distilled sandalwood essential oil.