Santalum acuminatum

Santalum acuminatum grows as a tall shrub, or small tree, 4 to 6 m (13 to 20 ft) high and 2–4 m (6.6–13.1 ft) wide. The rough bark is dark grey and the branches ascending in character. Smaller plants formed by suckers from the roots are sometimes found surrounding larger plants. The smaller branches have a more weeping habit.[3] The slender to ovate leaves are pointed at the tip, and are pale yellowish-green bringing a slightly grey and leathery appearance. These are supported on a short leaf stem, 5 – 10 mm long, the leaves themselves being 45 – 115 mm long. They are tapered in outline, and arranged in opposite pairs on the branchlets.[4]

Flowers can be green or creamy white on the outer parts, reddish or yellowish brown on the inner faces; these appear on stems, are just 2–3 mm across, and are fragrant.[5] Fruit is produced after 4 years and is red or sometimes yellow, measuring between 20 and 25 mm across. A 3-mm layer of flesh covers a brain-like nut with a hard shell that encases the seed. This fruit is referred to as a drupe. It ripens from green to a shiny red in late spring or summer, and is globe-shaped and 20 to 40 mm across.[6][7] The skin of the fruit is waxy.[8]

Roots are adapted to a hemiparasitic mechanism, using a haustorium, on roots able to reach out 10 m to other root systems.

The species shares the common name quandong with other plants, bearing similar fruit; it may be distinguished as the "desert" or "sweet". The name quandong usually refers to the fruit of S. acuminatum in commercial usage. Variant spelling includes quondong and quandang. The fruit and plant are also named sweet quandong and native peach.[3] The plant was known to many different indigenous language groups, and is therefore known by many different names. The Wiradjuri people of New South Wales used the name guwandhang, from which the name quandong was adapted. Other indigenous names include; wolgol (Noongar, South Western Australia)[9] gutchu (Wotjobaluk, Western Victoria); wanjanu or mangata[10] (Pitjantjatjara, Uluru), and goorti[11] (Narungga).

The species was first described by Robert Brown, named in Prodromus Florae Novae Hollandiae (1810) as Fusanus acuminatus, based on his type collection made at Fowlers Bay, South Australia, in 1802. Brown gave the Latin epithet acuminatus to denote the leaves – sharpened or pointed.[4] The botanist Alphonse Pyrame de Candolle gave the current name in 1857, placing it in the genus Santalum; the genus containing Australian sandalwood, Santalum spicatum, and white sandalwood, Santalum album.[12] Several botanical names have been deemed to be synonymous with Santalum acuminatum, as described in Flora of Australia (1984) and the Australian Plant Census (2006), these include: Santalum preissii F.Muell. in Fragmenta Phytographiae Australiae (1861); Santalum cognatum and Santalum preissianum of Miquel (1845); and Santalum densiflorum Gand. (1919).

Mida acuminata was given by Otto Kuntze in an attempted revision, as with Eucarya acuminata (R.Br.) Sprague and Summerh.

A number of cultivars have been named in application for plant breeders' rights, of which two have been accepted and another has been granted. The first named cultivar of the species was named Powell's # 1,[13] but application for legal recognition of this name was withdrawn.[14] The second is known as Powell's Red Supreme.[15] Two names are given as accepted applications in the Plant Varieties Journal: Powell's Red Supreme and Saltbush Lane.[16]

One variety of S. acuminatum is named in accordance with the International Code of Nomenclature for Cultivated Plants; following the publication of a description, Santalum acuminatum 'Frahn's Paringa Gem'[17] became the first cultivar to be receive legal protection.[18]

Santalum acuminatum is widely distributed throughout most southern regions of mainland Australia, including the arid centre of the country, and in some regions is common. The related Australian sandalwood, Santalum spicatum, was once more populous than this species; commercial exploitation has reversed this position.

The plant occurs in Western Australia's north to Carnarvon and Karratha (21 N), reaching inland from the coastal plains, and is found throughout Southwest Australia.[4] The number of recorded specimens in this region is low, and mainly restricted to coastal sandplains, its range having been impacted by altered land-use in the wheatbelt. Some populations are discontinuous in the distribution range, as with many species of the region, beyond the dispersal range of the seeds. Remote groups of the species are remnant to former distribution ranges, to different climates, and these may be isolated by hundreds of kilometres. The species is one of those in the region to include "wet outliers", small populations outside of the usual low rainfall habitat.[19]

Occurrence of the plant is also recorded in South Australia, Victoria, and New South Wales, and Queensland.[3] It is widespread in western New South Wales, eastwards to Dubbo and Culcairn.[20] It is rare in the northwest of the state.[21]

The plant is hemiparasitic, able to photosynthesize, but using the root system of other plants to acquire nutrients other than sugars.[7] The plant genus Santalum attaches to other species, in a nondestructive way, sustaining itself by their provision of nitrogen, shade, and water.[4] The roots of the species have pad-like adaptations, that nearly encircle the host's root, which is typical of this genus of sandalwoods. Hosts can be other trees, or grasses, usually several plants are used. The taxa recorded in this relationship are species of genera; Acacia, Maireana, Atriplex, and many others, including hemiparasites such as Exocarpos sparteus. This mechanism allows the plant to acquire 70% of its nitrogen, and some of its water requirements from the roots of other trees and shrubs.[22]

The tree occupies a diverse and widespread range of habitats, including creek beds, granite, gravel plains, and sandy dunes. It is tolerant of drought, salt, and high temperatures, and need not have a nutrient-rich environment. The seedling can become established in the shade of its host, reaching for full sun once developed, so the plant is usually intermingled with host and other species.

The environs of the distribution range are subject to frequent bushfires, this requires the plant to regenerate from its roots, so the species is rarely found as an advanced tree. Those specimens exposed to bushfire and soil disturbance occur as sprawling multistemmed shrubs. The plant's regrowth from the root system gives this species a lead over shrubs that recur from seed. Trees with a single main stem are in locations remote from these factors. The habit of older trees may overwhelm the adjacent plants by monopolising the sunlight and parasitising roots of plants beyond its own canopy.

The foliage, being much paler than other trees and shrubs, makes the plant conspicuous in bushland and scrub. An occurrence of an unmolested specimen is recorded at Woodman Point in Western Australia, an area remote from the high-intensity fires of altered regimens.

Emus eat the fruit, and it forms an important part of their diet; the nut remains undigested in their droppings. This is the usual method of S. acuminatum seed dispersal, when it is within the emu's range.

A number of species interact with this plant, in a number of complex relationships, a noted example being Paraepermenia santaliella, the quandong moth of the family Epermeniidae. Other creatures, such as larvae of nitidulid beetles and the wood white butterfly, also feed on S. acuminatum.

A desert quandong nut on a piece of paperbark

The fruit and nut were important foods to the peoples of arid and semiarid central Australia, especially for its high vitamin C content.[10] It is commercially grown and marketed as a bush food and is sometimes made into a jam, an enterprise begun in the 1970s. It is well known as an exotic food.

The oil of sandalwoods, primarily Santalum album, was described and investigated by pharmacologists. The more widely known Australian sandalwood, S. spicatum, was extensively harvested and exported, leaving S. acuminatum as the more common Santalum in many regions.

The established use of the fruit, by Aboriginal peoples, was acknowledged by the early settlers of the colonies; this product was made into jam and chutney. The fruit is frequently mentioned in natural histories and botanical works, such as Flowers and plants of Western Australia,[8] and traded as a commodity, however, the kernel of the seed has, historically, been the most extensively used.

Colonial ethnic groups did not attempt to domesticate indigenous plants in Australia, despite being known and occasionally used, but the great demand from export markets to Singapore, Britain, and elsewhere led to financial backing of growers and enthusiasts. The backyard of Dudley and Lyla Frahn in Paringa, South Australia, contained an orchard of quandongs. The couple recorded yield and qualities of the fruit, one of which became the source for the variety registered and marketed as Frahn's Paringa Gold.[30]

• Quorn Quandongs
• Quandong moth and other pests
• The Desert Quandong
• Australian Quandong Industry Association
• The Quandong Story