Your web browser is out of date

For the best experience, please upgrade. Learn more

Aroma Science

Harvesting and Processing Sandalwood

Although sandalwood trees are typically ready to harvest for their essential oil when they are between 10-15 years old, many experts believe that waiting even longer is key to achieving the most desirable oil. A recent study states that it’s better to wait for harvest until the trees are 25 years old.  According to a recent  study in the Australian Sandalwood Network publication, “Trees aged 8-11 years contained only low-grade wood, those aged 14 years contained only 12 % high-grade wood (butt wood only), while those aged 26 years contained 67 % high-grade wood in the butt, root,s and large stems.” However, even the best quality wood from the 26-year-old trees was still of a lower quality and produced less oil than the wood harvested from the wild sandalwoods, often thought to be over 100 years old.

(source, 2012).

Among many sandalwood cultivation companies, trees are harvested based on size, rather than exact age. In Queensland, for example, trees of S. lanceolatum are considered ready for harvest if they meet a set of precise measurements: the tree’s diameter must be greater than 12 cm, and the sapwood must be less than 1/6 the diameter of the tree at 1.3 m above the ground. Sandalwood harvesters take these measurements by chopping into the tree’s trunk rather than cutting down the entire tree, a procedure which protects the sandalwood trees that are not ready from being unnecessarily chopped down.

In both India and Western Australia, dead-standing or fallen trees of any size can be harvested, as the wood retains oil for many years after the tree itself dies. In some parts of India and Western Australia, dead trees form much of the overall harvest. (USDA, source, 1990).

In the species S. album, S. spicatum, and S. austrocaledonicum, the stump and larger roots are also harvested, as they contain the best quality wood and highest oil content.Older and larger sandalwood trees contain a higher proportion of heartwood.  The heartwood is the rich, oil-producing wood located beneath the tree’s outer layer of sapwood, and a higher proportion of heartwood in a sandalwood tree means a higher proportion of sandalwood oil. The heartwood can be found in the tree’s trunk and branches, as well as its stump and roots, which have the highest oil content. The ratio of heartwood to sapwood varies between species and even within species, especially in the Hawaiian sandalwoods.

(USDA, source, 1990).

Because most of the sandalwood oil is in the tree’s heartwood, this part of the tree is essential to the harvest and distillation process. One of the traditional ancient methods of sandalwood oil production was to bury the harvested timber in the ground so that ants would eat the outside sapwood, leaving the central heartwood uneaten as its sandalwood oil and the resulting fragrance repelled them. Today, the sandalwood’s sapwood is sawed and ground away to reach the oil-rich heartwood.

(Base Notes, source, 2013).

Although the heartwood is the most valuable, the whole tree is used in the production process, including its sawdust. Markets do exist for the sapwood of S. album, S. spicatum, and S. austrocaledonicum because the sapwood does contain a small amount of sandalwood oil.

(USDA, source, 1990).

After harvest, the timber is graded using a system that designates lower grades of sandalwood, such as chipped branches and even sawdust, to be used for incense; higher-grade logs are typically used in carving (from small objects to furniture). In preparation for oil distillation, the timber is chopped into woodchips approximately a centimeter long and then reduced to a powder. Most sandalwood oil is now produced by steam distillation of this powder. The steam distillation process can take up to a week, as the sandalwood oil is held very tightly within the grain of the wood.

(Base Notes, source, 2013).