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 warm greenhouse[]. The dehusked seed germinates quickly at 25°c[]. The seed can also be sown in the spring in a warm greenhouse[]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. If trying them outdoors, give the plants some protection from the cold for their first few winters.
Cultivars may be grafted.