Common Name: Queensland Nut

General Information

Macadamia tetraphylla is an evergreen tree that can grow up to 16 metres tall, but is usually smaller. The plant has long, narrow, thorny leaves[].
The tree is particularly valued for its edible seed, considered by many to be one of the most delicious seeds in the world[]. The seed of this species is not as good a quality as the seed of M. Integrifolia and so the plant is less important commercially[]. It is cultivated for its edible seed in many tropical and sub-tropical areas, particularly Hawaii[, ].

Known Hazards

None known

Botanical References

,

Range

Australia - New South Wales, Queensland.

Habitat

In or near rainforests[]. Found mainly on alluvial situations bordering rivers and creeks where the fertile volcanic soils are rich in humus[].

Properties

Edibility Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Growth Rate	Slow
Pollinators	Bees
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Macadamia tetraphylla succeeds in cool tropical or subtropical climates - in Australia they fruit well even when growing at least as far south as Sydney[, ]. In the tropics the plant fruits best at elevations from 1,000 - 1,500 metres. It grows best in areas where annual daytime temperatures are within the range 14 - 28°c, but can tolerate 8 - 38°c[]. When dormant, the plant can survive temperatures down to about -2°c, but young growth can be severely damaged at -1°c[]. The plant can survive slight frosts, though cold weather can result in the loss of the entire crop[]. It prefers a mean annual rainfall in the range 1,250 - 2,000mm, but tolerates 850 - 3,000mm[].
Plants grow best in rich moist but well-drained soils and a position in full sun[]. They require copious summer watering in their early stages[]. Prefers a pH in the range 5.5 - 7, tolerating 4.5 - 8[]. Trees require a sheltered position and are easily damaged by strong winds[, ].
Plants are slow growing in cultivation, seedlings take 6 - 7 years to produce their first fruit[, ]. The trees then produce commercial crops for about 40 - 50 years and can fruit for up to 100 years[].
There are some named varieties[, ].
Plants are self-fertile but yield better if cross-pollinated[].
Pruning is not normally necessary, but is tolerated if carried out in the autumn[].

Edible Uses

Seed - raw or cooked[, , ]. Pleasantly flavoured and nutritious[, ], the seed is a little sweeter than the related Macadamia integrifolia and contains a little less oil[]. They can be eaten as a dessert nut and can also be ground into a 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 is up to 30mm long and 24mm wide[].

The seed contains up to 72% of a high grade oil[, ]. This oil is seldom extracted due to the high value of the seed[].

Medicinal

None known

Agroforestry Uses:

The decomposed husk is commonly used in potting soil[].

Other Uses

Macadamia shells may be used as fuel, generating sufficient energy to dry wet, in-shell nuts[].

The oil from the seed is used in cosmetics[].

The green seed hulls contain approximately 14% of tannins[].

The tree is used as a rootstock for M. Integrifolia[].

Propagation

Seed - best sown as soon as it is ripe in a nursery bed[]. The dehusked seed germinates quickly at 25°c[].
Cultivars may be grafted. Side wedge grafting has been used exclusively in Hawaii[].

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