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Santalum - A Fascinating Genus
Santalum belongs to the family Santalaceae, which has over 30 genera and 400 species in tropical and temperate parts of the world. In Australia there are 10 genera, 4 of which are endemic. All Australian genera, except one, Dendromyza, are root parasites, ie their roots attach themselves to the roots of other plants and obtain nutrients from them. Dendromyza is a stem parasite, similar to mistletoes, although mistletoes belong to a different family.
Of the Australian genera, the most common locally is Exocarpos. The cherry ballart or brush cherry (Exocarpos cupressiformis) is widespread in eucalypt forest from south-east Queensland to South Australia and Tasmania. Also seen are the native currant, Liptomeria acida, with white flowers and edible fruit and Choretrum
candollei, which makes an attractive shrub in full flower.
Santalum has about 25 species spread from India and Malaysia through Australia and to islands of the Pacific. In Australia, we have five endemic species and one that occurs almost throughout the range of the genus. The Australian species are known as sandalwoods or quandongs.
Santalum obtusifolium - A sandalwood
This species occurs from the Lamington Plateau in SE Queensland through eastern New South Wales to East Gippsland. It is found along creek banks in forests in sand or gravelly clay.
It is a medium sized shrub to 2.5 m and is the only Santalum species with prominently recurved leaf margins. It has small axillary whitish flowers and purple succulent fruits about 1 cm diameter.
Little information is available about the uses of its fruit or timber.
Santalum lanceolatum - Northern sandalwood
This is the most widespread species in the genus. It occurs over a wide area but is more common in northern regions. Found mainly on sandy soils on sandplains or shrublands often with spinifex (Triodia spp.) or occasionally on creak banks and gullies.
It forms a shrub to 7 m with fissured grey bark and pendulous branches with grey, lanceolate leaves to 9 cm. The tiny cream or pale green flowers are borne in terminal or axillary clusters and the fruit is about 1 cm diameter changing from red to purplish black when mature. It has a prominent circular scar at its apex.
The fruit is edible and the explorer, Leichhardt, remarked it had 'a very agreeable taste'. It was eaten by Aborigines, who also mashed the roots and soaked them in water to make a liniment. The seeds were also ground to a paste and used in
the same way.
The timber is aromatic and limited exports have been made to Asian counties for its value as an oil source and for its fragrant timber.
Santalum murrayanum - Bitter quandong
The bitter quandong is found on gravelly and sandy loam and sometimes on dunes, in open woodland and tall shrubland. It occurs in the south of Western Australia, South Australia and south-west Victoria.
It forms a shrub or small tree to 4 m high with smooth bark and a more or less rounded habit. The narrow lanceolate leaves have a hooked tip and are pale yellowish green to 3.5 cm long. The small yellow flowers are borne in large clusters and are followed by large globular fruit about 2 cm diameter. When ripe
they are brownish red.
The fruit has a very bitter taste but the aborigines are said to have eaten the seeds and bark of the roots after roasting. The large seed has the typical rough and pitted shall, which may have been used to make Chinese checkers.
Santalum spicatum - Sandalwood
This species grows on loam and among rocks in woodland and tall shrubland. It occurs mostly in the southern half of Western Australia and in South Australia.
It is a medium to large shrub to 4 m with a spreading habit and rough, grey bark. The grey green lanceolate leaves are flat with a blunt tip and up to 7 cm long. The small red-green four-petalled flowers are scented and borne in clusters. The globular fruit is green to brown and about 2 cm diameter.
The timber of this species yields the valuable sandalwood oil, which is used in religious rites by Hindus, Buddhists, Parsis and Moslems in South-east Asia. It is presently harvested in the Goldfields area of Western Australia and sells for about $10,000 per tonne.
It is interesting to look at some historical figures on exports of sandalwood. In 1849,1204 tons of sandalwood, valued at £ 10,711, were shipped from WA and by 1899,4,470 tons worth £ 33,525 were sent to Singapore and China. At this time it was stated that all sandalwood trees of any size were cut down within a radius of 150 miles from Perth. In 1890, the Sydney Morning Herald reported that a Distillery Company had been established near Albany and the first instalment of twenty cases of sandalwood oil was shipped to England. Exports of timber continued to grow until in 1920, more than 14,000 tons of wood left from WA.
Despite these huge export quantities, this species is said to produce an inferior oil to the Indian sandalwood (S.album) and has a rotation sequence of about 100 years compared to a rotation period of 20-30 years for S.album. Nevertheless plantations are being established in WA to capitalise on this market.
Santalum acuminatum - Native peach or Sweet Quandong
This species is widespread in drier areas of southern Australia and may be found on coastal dunes, gravelly plains, granitic outcrops and creek banks. It is not fussy about soil type or its host plant, which may be a perennial grass or a legume or herb.
The tree in its natural habitat (left)
The fruit (right)
Photos: Horst Weber
Click for larger image
It forms a shrub or small tree to about 6 m high and sometimes spreads by underground stolons. The yellowish green leaves are up to 9 cm long and tiny yellowish flowers are borne in large terminal clusters. The fruits are bright shiny red and vary in diameter from 15-50 mm diameter. The flesh is easily removed from the seed when ripe. The kernel is pitted similarly to S.murrayanum.
Much research has been carried out on the potential value of native peach as an edible crop for growing in semi-arid and arid areas. This began in 1973 when an experimental plantation was established near Quorn, SA by the CSIRO, Division of Horticultural Research.
Germination was difficult with fungal problems affecting the viability of old seed. Fresh fruit had to be collected and the flesh removed. The kernel was then placed in a vice and carefully cracked to remove the seed, which was placed in moist sterilised vermiculite and held at temperatures between 15-20o. Germination may take from one to 12 months and a 70% germination rate could be expected. Later work indicated that by planting whole kernels directly into well-drained Dotting mix and keeping the pots at about 20oC, similar germination percentage was achieved although the germination time may be longer.
When the seedlings were about 5-10 cm high, a host plant was introduced into the pot. Lucerne was considered to be a suitable host species. As the tap root of S.acuminatum grows much quicker than the shoot, it is important to place the plant in the ground as early as possible with spring considered the optimum time.
Jam and chutney made from sweet quandong
As seedling plants exhibit genetic variation the next move was to attempt to graft good fruiting clones. This is now being done commercially in the Mildura area and successful plantations have been established.
The fruit may be eaten raw, but the main commercial use is for jams, jellies, chutneys and in pies. It is available in specialty shops.
An Australian Quandong Industry Association Inc. has been formed and a host of useful information is available from them.
Santalum album - Indian sandalwood
Despite the common name S.album is an Australian native plant occurring along the coast and adjacent islands between Melville and Elcho Islands (north coast of the Northern Territory). It grows in sand in shrubland behind mangroves and by billabongs.
This species looks rather different to the other native Santalum spp. in that it often forms a dense shrub to 4 m high with glossy ovate leaves to 7 cm long with obvious veining on the underside. The small red or greenish flowers are borne in axillary or terminal clusters and the black fruit is only about 7 mm diameter. It is edible.
The great value of this species is its timber and the oil that it contains. Like S.spicatum it is used in religious ceremonies and carvings in South-east Asia, India and China.
Experimental work is in progress on the Ord River Scheme, near Kununurra, WA to cultivate this species to exploit the rich markets of the Asian area, where the species is becoming rare. Like the other species of Santalum, Indian sandalwood is a root parasite and will not grow well unless it has access to a suitable host, so much of the research has been directed to this end.
On germination of the seed, a pot host is required and currently an Alternanthera sp. is being used. This plant combination is then planted out and a secondary host, which may be an Acacia sp. or Sesbania formosa is planted 1 metre or so from the target species. Finally the ultimate host plant is established in the same area. Considerable research is under way to determine the optimum, tertiary host, with the native dry rainforest tree, Cathormium umbellatum, a legume, currently being preferred. Further research, however, is aimed at making the final host a species with commercial value. Valuable timber trees such as several Dalbergia spp., Kaya senegalensis and even the Australian red cedar Toona ciliata, are being examined.
Indian sandalwood takes about 20 years to be suitable for harvest, with the present expected value of the wood being in the order to A$20,000 per tonne.
Indian sandalwood may be used in three ways.
- The oil may be extracted from the butt of the tree and used in cosmetics.
- The timber may be used for carvings
- The timber may be burned as incense sticks.
Finally the genus Santalum holds a special fascination to me not only because of its semi-parasitic nature but because several potentially valuable products may provide important export markets of the future.
From the April 2003 issue of Native Plants for New South Wales, newsletter of the Australian Plants Society (NSW).
John Wrigley is a well known author and horticulturist and life member of the Australian Plants Society (NSW). He is a former curator of the Australian National Botanic Gardens and the author of many books and articles. His best known publication is Australian Native Plants (jointly with Murray Fagg) which was first published in 1979. The much updated and revised 5th edition is expected to be published later in 2003.
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Australian Plants online - September 2003
Association of Societies for Growing Australian Plants