Macadamia tetraphylla

Macadamia tetraphylla

The macadamia nut or bauple nut, prickly macadamia, Queensland nut, rough-shelled bush nut and rough-shelled Queensland nut (Macadamia tetraphylla L.A.S. Johnson 1954) is an arboreal species belonging to the Proteaceae family.

Systematic –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Plantae,
Subkingdom Tracheobionta,
Spermatophyta Superdivision,
Division Magnoliophyta,
Class Magnoliopsida,
Subclass Rosidae,
Proteales Order,
Proteaceae family,
Subfamily Grevilleoideae,
Tribe Macadamieae,
Subtribe Macadamiinae,
Genus Macadamia,
Species M. tetraphylla.

Etymology –
The term Macadamia is in honor of the scientist and politician John Macadam (1827-1865), colleague of the botanist Ferdinand von Mueller who first described them.
The specific epithet comes from the Greek words “tettares”, i.e. four and “phyllon”, i.e. leaf, in reference to the leaves often arranged in whorls of four.

Geographic Distribution and Habitat –
Macadamia tetraphylla is a tree native to southern Queensland and northern New South Wales in Australia.
This species was then introduced into Mexico with good results in the states of Michoacán and Jalisco, where it has become an important export crop for the Mexican market.
Its natural habitat is that of coastal areas of subtropical rainforests on hilly slopes, where it grows up to around 450 m altitude.

Description –
Macadamia tetraphylla is an evergreen tree, with a crown composed of dense foliage, which grows between 3 and 20 meters in height.
It is a very branched tree, with a cylindrical trunk and smooth or slightly fissured greyish-brown bark.
The leaves are sessile or subsessile, usually arranged in whorls of 4, rarely 3 or 5, they are simple, leathery, oblong to oblanceolate in shape, 7-25 cm long and 2-4.5 cm wide, with apex more or less pointed and spiny-toothed margins, shiny dark green in color while that of the young leaves ranges from bronze to purple.
The inflorescences form in the axils of the branches, are 8-35 cm long, covered with a dense yellowish brown tomentum; they are made up of hermaphroditic flowers with tomentose perianth, 0.6-1.5 cm long, generally pink to purple in colour, pollinated by insects, in particular bees.
The fruit is globular, 2-3.5 cm in diameter with a fleshy and fibrous mesocarp of a grey-green color tending to brown, which often opens when ripe, and a particularly hard, wrinkled, shiny brown woody endocarp.
Inside there is a single globular seed of 1.5-2 cm in diameter, darker than that of the edible Macadamia integrifolia.

Cultivation –
Macadamia tetraphylla is a tree particularly appreciated for its edible seed, considered by many to be one of the most delicious seeds in the world, although of lower quality than M. Integrifolia and therefore the plant is less important from a commercial point of view.
The cultivation requirements and the processes to which the fruits are subjected are practically identical to those of Macadamia integrifolia, to which we refer. For its foliage and ornamental inflorescences, and in particular for the new vegetation which is very decorative due to its colour, it is sometimes used in parks and gardens in tropical and subtropical countries. The species is now rare in nature, due to the exploitation of the territory, and considered at risk of extinction in the near future.
The plant is however cultivated for its edible seeds in many tropical and subtropical areas, in particular in Hawaii while in the areas of origin it grows mainly in alluvial soils that run along rivers and streams where the fertile volcanic soils are rich in humus.
This plant thrives in cold tropical or subtropical climates: in Australia it bears fruit well even up to the latitude of Sydney.
In the tropics the plant bears fruit best at altitudes between 1,000 and 1,500 metres. It grows best in areas where annual daytime temperatures are between 14 and 28°C, but can tolerate 8-38°C.
In a dormant state it can survive temperatures down to about -2°C, but new shoots can be severely damaged at -1°C. The plant can survive light frosts, although the cold can result in the loss of the entire crop.
From a pluviometric point of view, it prefers an average annual rainfall between 1,250 and 2,000 mm, but tolerates 850 – 3,000 mm.
From a pedological point of view, the plants grow best in rich, moist but well-drained soil and in a position in full sun, even if they require abundant summer watering in the initial stages; They prefer a pH between 5.5 and 7, tolerating 4.5 – 8.
Trees also require a sheltered position and are easily damaged by strong winds.
The plants grow slowly in cultivation, the seedlings take a few years to produce the first fruit; after which they produce commercial crops for about 40-50 years and can fruit for up to 100 years.
These are self-fertile plants that produce best when cross-pollinated.
Pruning is not normally necessary, but is tolerated if carried out in the autumn period.
Reproduction occurs by seed, which has a germination duration of up to about six months, previously kept in water for 24 hours, in sandy loam rich in organic substance kept humid at a temperature of 22-25 °C.
It germinates in 1-4 months and takes, as mentioned, 7-12 years to enter production; to preserve a given variety and shorten the time it takes to go into production, grafting onto plants of around one year of age is used, with the first flowering after 2-3 years, and layering.
It hybridizes easily with Macadamia integrifolia. The species is less commercially exploited than Macadamia integrifolia, even if it adapts to cooler climates, as the seeds have a lower oil content and organoleptic characteristics, the main use is as its rootstock due to its greater resistance to diseases.

Customs and Traditions –
Macadamia tetraphylla was described by Lawrence Alexander Sidney Johnson and published in Proceedings of the Linnean Society of New South Wales 79 (1): 15–16. 1954.45.
This plant is known by various common names, including: macadamia nut, prickly macadamia, Queensland-nut, rough-leaved Queensland nut rough-shelled macadamia, rough-shelled Queensland-nut (English); si ye ao zhou jian guo (Chinese); macadamia à coque ridee, macadamier, noisetier d’Australie, noix de macadamia, noix du Queensland, noyer du Queensland (French); macadâmia, nogueira-macadâmia, noz de macadâmia (Portuguese); nogal de Australia, nuez australia, nuez de macadamia (Spanish); Macadamianuß, rauhschalige Macadamia (German).
The plant, from its original territory, was subsequently introduced to other countries including Mexico where it had good results in the states of Michoacán and Jalisco, becoming an important export crop for the Mexican market. Hawaii is the largest exporter of this crop globally. Both Macadamia species have been unsuccessful in the pure tropics, with no fully successful plantings within 15 degrees of the equator. The main plantations in Costa Rica, 10 degrees north, are said to produce much less than in Hawaii, 19-22 degrees north, in one case 20% of production. Plantations in Guatemala at 15 degrees north are successful. However, individual seedlings have produced well in the pure tropics and must be selected.
Macadamia tetraphylla has a higher sugar content than integrifolia, which leads to burning problems when baking in biscuits and other desserts, so most commercial macadamias are of the integrifolia species to ensure conformity of roasting results and cooking. Many tetraphylla or hybrids of tetraphylla and integrifolia are grown in home orchards. Some prefer the higher sugar content of tetraphylla, especially for raw consumption.
Macadamia tetraphylla was the first native Australian food plant to be grown by non-indigenous Australians as a commercial crop. The first commercial plantation of macadamia trees was planted in the early 1880s by Charles Staff at Rous Mill, 12 km south-east of Lismore, New South Wales, consisting of M. tetraphylla. Seedlings from the original plantation were used as rootstocks for modern grafted varieties well into the 20th century. This original planting was finally eliminated and replaced with modern varieties grafted in the 1990s.
Ironically, although the macadamia has spread around the world in commercial agriculture, it is now listed as a vulnerable species in its native Australia due to habitat loss and degradation. The loss and impoverishment of its habitat is the result of the clearing of lowland rainforest for agriculture and urban development; weeds; and poorly designed fire management systems.
Like many other nuts, as well as olives, macadamia nuts are rich in monounsaturated fatty acids (containing about 86%). Monounsaturated fatty acids have been linked to reducing blood cholesterol.
Other uses of this plant include as a fuel, generating enough energy to dry moist nuts in their shells.
Furthermore, the seed oil is used in cosmetics.
Green seed shells contain about 14% tannins.
Decayed husk is commonly used in potting soil.
The tree is used as a rootstock for M. Integrifolia.

Preparation Method –
Macadamia tetraphylla is a plant used mainly for food use or as a rootstock.
In food use, the seeds are used raw or cooked.
They are pleasantly aromatic and nutritious. The seed is a little sweeter than Macadamia integrifolia and contains a little less oil.
The seeds can be consumed as dried fruit desserts and can also be ground into flour and then mixed with cereal flours to enrich the protein content. The shell is very hard, making it difficult to extract the seed.
The seed contains up to 72% of a high-quality oil; this oil is rarely extracted due to the high value of the seed.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (ed.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora d’Italia, Edagricole, Bologna.
– Treben M., 2000. Health from the Lord’s Pharmacy, Advice and experiences with medicinal herbs, Ennsthaler Editore.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/4718987/original.jpeg
– https://media.api.aucklandmuseum.com/id/media/v/373245?rendering=original.jpg

Attention: Pharmaceutical applications and food uses are indicated for informational purposes only, they do not represent in any way a medical prescription; we therefore decline any responsibility for their use for healing, aesthetic or food purposes.