Macadamia integrifolia

Macadamia integrifolia

The Bauplenut or bopplenut, bushnut, macadamia nut, Queenslandnut, smooth-shelled macadamia, smooth-shelled Queensland-nut (Macadamia integrifolia Maiden & Betche 1896) 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. integrifolia.
The term is synonymous:
– Macadamia ternifolia var. integrifolia (Maiden & Betche) Maiden & Betche.

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 integrifolia comes from the Latin “integer, -gra, -grum”, i.e. whole and “folium”, i.e. leaf, in reference to the entire margins of the leaves.

Geographic Distribution and Habitat –
Macadamia integrifolia is a plant native to Australia (north-eastern New South Wales and south-eastern Queensland).
Its natural habitat is frequently that of the dry subtropical rainforests of the eastern coastal scrub and found mainly in alluvial situations bordering rivers and streams where the fertile volcanic soils are rich in humus.

Description –
Macadamia integrifolia is an evergreen tree that can reach approximately 15 – 18 meters in height, with thick and compact foliage.
The leaves are simple leathery, borne by a 0.5-1.5 cm long petiole, generally arranged in whorls of three, from oblong to oblanceolate, 8-20 cm long and 2-6 cm wide, with an entire or irregularly provided margin of thorns and sharp or obtuse apex, of a shiny dark green colour.
The inflorescences are formed in the axillary position; they are simple, pendant, 8-25 cm long, made up of 100-300 scented hermaphroditic flowers with a 0.5-1.2 cm long perianth of white or cream colour, pollinated by insects.
The fruits are globose drupes of 2-3.5 cm in diameter with a fleshy and fibrous green mesocarp, which often opens when ripe, and a particularly hard woody endocarp, of a shiny brown colour.
Inside there is generally a single globular seed, 1.2-2.5 cm in diameter, commonly called macadamia nut, which is the edible part.

Cultivation –
Macadamia integrifolia is a very beautiful evergreen tree, which is particularly prized for its edible seed, considered by many to be one of the most delicious seeds in the world.
The plant is often grown for its shade and as an ornamental in the tropics, and is also grown for its edible seeds in several tropical and subtropical areas, particularly Hawaii.
The seeds are traded internationally.
M. integrifolia is a plant from the subtropical and tropical areas of eastern Australia. It has quite stringent environmental requirements if good seed crops are to be produced. In the tropics it bears fruit best at altitudes between 1,000 and 1,600 metres, but can reach sea level in subtropical areas.
It grows best in areas where annual daytime temperatures are between 10 and 26°C, but plants can tolerate 8-35°C.
Mature plants are capable of withstanding moderate frosts, but only for short periods.
It prefers an average annual rainfall between 1,000 and 3,000 mm, but tolerates 700 – 3,500 mm.
For its cultivation it requires a sunny position and rich, moist but well-drained soil which requires abundant summer watering in the initial stages.
From a pedological point of view, they prefer a pH between 5 and 6, tolerating 4.5 – 7. The established plants are very resistant to drought but require a sheltered position and are easily damaged by strong winds.
The beginning of flowering occurs when temperatures drop and the trees become dormant in autumn, the optimal temperature is 18 °C.
Plants remain dormant for 50 – 96 days; the racemes extend after an increase in temperature and some rain.
Seedling growth is slow initially, but gains momentum as the saplings produce a series of extending growth blooms in a year.
The juvenile phase lasts 7 years or more, but the grafted trees come into production after 3 years.
The plants grow slowly in cultivation, especially when young, the seedlings take 6 – 7 years to produce the first fruit.
The trees then produce commercial crops for approximately 40-50 years and can bear fruit for up to 100 years.
The trees can flower and produce fruit all year round.
In Hawaii, yields of 45 kg of in-shell walnuts are obtained from better trees, which is an average of 3.2 – 3.5 t/ha per year.
Pruning is not normally necessary, but is tolerated if carried out in the autumn period.
The flowers are subject to fungal attacks, in particular by Botrytis cinerea, in situations of high humidity and poor ventilation, and the root system to rot by various pathogens, the most common by Phytophthora cinnamomi, in situations of poor drainage and prolonged water stagnation . The fruits are perfectly ripe when they fall from the tree, therefore they must generally be collected manually, which is one of the reasons for the high cost of the product, and within 24 hours of harvesting they must be mechanically deprived of the mesocarp, which is recycled in the plantation, then sent to drying systems, a fundamental process because it causes the seed to detach from the shell, avoiding damage when it breaks, and improves its organoleptic characteristics; Special devices have been created to break the very hard shell.
The plant reproduces by seed, previously kept in water for 24 hours, in sandy soil rich in organic substance kept humid at a temperature of 22-25 °C, which germinates in 1-2 months and takes 7-12 years to enter into production , but the quality is not predictable; 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 tetraphylla.

Customs and Traditions –
Macadamia integrifolia is a plant known by various common names; among these are: bopplenut, bushnut, macadamia nut, Queenslandnut, smooth-shelled macadamia, smooth-shelled Queensland-nut (English); ao zhou jian guo (Chinese); macadamia à coque lisse, macadamier, noisetier d’Australie, noix de macadamia, noix du Queensland, noyer du Queensland (French); macadamia, Queensland walnut, macadamia nut (Italian); macadâmia, nogueira-do-havaí, nogueira-macadâmia, noz de macadâmia (Portuguese); avellano de Australia, macadamia, nuez australia, nuez de macadamia (Spanish); echte Macadamianuß, glattschalige Macadamia, Macadamianuß (German).
The fruit is rich in oil and is extracted and used in the food and cosmetics industry. It requires a high quantity of water and minimum temperatures of 10 °C.
Commercially produced macadamia nuts derive mostly from selected varieties of Macadamia integrifolia and its hybrids with Macadamia tetraphylla, more resistant than the first, but which gives a slightly lower quality product. Walnuts contain 72-75% oil, of which more than 77% is monounsaturated fat, and about 8% protein, as well as minerals and vitamins. They are consumed raw or roasted, or used ground to package various dishes and confectionery products, the oil is used for cooking and in the soap and cosmetics industry. Finally, the ornamental characteristics of the tree should not be underestimated, often used in parks and gardens in tropical and subtropical areas for its foliage and decorative, scented inflorescences.
Other uses include agroforestry uses. The decomposed peel is commonly used in potting soil and the presence of macadamia also retards the growth of papaya trees planted near it.
Macadamia shells can be used as fuel, generating enough energy to dry moist in-shell nuts.
The seed oil is used in cosmetics.
Green seed shells contain about 14% tannins.
Please remember that macadamia nuts are toxic to dogs and cats.

Preparation Method –
Macadamia integrifolia is a plant used for food purposes as well as for various uses including ornamental ones.
The seed is eaten raw or cooked. The fine, crunchy texture, rich cream color and delicate flavor make the macadamia nut one of the most prized dessert nuts.
The edible quality of the nut is enhanced by light roasting in coconut oil and salting.
They are sweet and delicious and the seeds can also be added to cakes, biscuits, ice cream etc. They can be ground into a flour and then added to cereals to enrich their protein value. The shell is very hard, making it difficult to extract the seed.
An edible oil can be obtained from the seed although it is rarely extracted due to the high value of the seed.
The seed contains the highest level of oil ever found in a nut (up to 75%).
The oil contains 80% monounsaturated fats and 8% omega-6 fatty acids.
It has a subtle, nutty flavor and is added to salads, used in cooking, etc.

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://en.wikipedia.org/wiki/File:Proteaceae-_Macadamia_integrifolia_%28macadamia_nut%29_3.jpg
– https://cdn.plantatlas.org/img/specimens/USF/273475.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.