Macadamia

Macadamia integrifolia and Macadamia tetraphylla

Synonyms -

Family: Proteaceae

Names:

Macadamia celebrates the Australian chemist, medical teacher and politician John Macadam.

Other Names:

Bauple nut, bush nut, Hawaii nut and Maroochy nut.
Aboriginal names include Bauple, gyndl and jindilli.
Macadamia tetraphylla has the following common names;
Rough-leaved Queensland nut,
Rough-shelled Queensland nut.
Macadamia integrifolia has the following common names;
Macadamia nut,
Queensland nut.

Summary:

A small to medium sized tree, with opposite, glossy leaves in sets of 3-4 usually. The flowers are white to pink. Macadamia integrifolia and its hybrids are the species most commonly cultivated for its fruit.

Description:

Cotyledons:

Two.

First leaves:


Leaves:

Macadamia tetraphylla - Leaves mostly in whorls of 4 (rarely 3 or 5), base very obtuse, sessile or petioles less than 3 mm, new growth reddish.
Stipules -
Petiole - 0-3 mm long.
Blade - elliptic, 180-250 mm long by 20-50 mm wide, leathery, hairless, 13-20 pairs of main lateral veins. Tip pointed, sides toothed with somewhat prickly teeth, base tapering.
Macadamia integrifolia - Leaves mostly in whorls of 3 (rarely 4 or paired or single), base narrow cuneate, petiole >5 mm, new growth pale green.


Stipules -
Petiole - 5-10 mm long.
Blade - elliptic to egg shaped, 70-150 mm long by 20-40 mm wide. Tip rounded, sides entire or with coarse prickly teeth, wavy (undulate), hairless, 7-12 pairs of main lateral veins
Stem leaves -

Stems:

Woody trunks
Flower stem - Fruit and flowers are borne on second year wood.

Flower head:

Flowers in pairs and sessile. Axillary and produced on the woody branches of last seasons growth (ramiflorous).
Long, slender, simple raceme.
Macadamia tetraphylla flower head is 100-250 mm long, densely hairy.
Macadamia integrifolia flower head is 100-200 mm long, sparsely hairy.

Flowers:

Ovary - Sessile, hairy, 2 ovules. Style thread like and elliptical at the top.
Perianth - 4 white to creamy pink to mauve tepals. 8-12 mm.
Stamens -
Anthers - On short filaments

Fruit:

Single, spherical, smooth. 20-35 mm diameter, greyish green turning brown.
Hard, woody, follicle with one or two seeds
Edible.

Seeds:

15-30 mm, pointed at the tip and lumpy.

Roots:

Shallow.
Exposed trees often blow down in storms.

Key Characters:

Whorled leaves, young shoots glabrous.
Style tip swollen.
Flowers sessile, white to pink.
Fruit globular, >15 mm diameter, indehiscent, brown when ripe.
Small to medium tree.

Biology:

Life cycle:

It takes 7-10 years to produce commercial quantities of seeds. Once established it may continue bearing for over 100 years.

Physiology:

In 100-gram sample, macadamia nuts have 740 calories and are a rich source of numerous essential nutrients, including thiamine, vitamin B6, manganese, iron, magnesium, and phosphorus. Macadamia nuts are 76% fat, 14% carbohydrates, 8% protein and 9% fiber.

They have a high amount of monounsaturated fats (59%) and contain the monounsaturated fat, omega-7 palmitoleic acid as 17% of the total fat,

Reproduction:

Mainly propagated by grafting

Flowering times:

Macadamia tetraphylla - August-October. Fruit ripe in January.
Macadamia integrifolia - Fruit ripe in July.

Seed Biology and Germination:


Vegetative Propagules:

Often grafted.

Hybrids:

A Macadamia integrifolia x Macadamia tetraphylla hybrid is a common commercial variety that is widely planted in Australia and New Zealand and bears useful amounts of fruit after it is four years old.

Allelopathy:

Ecology, Population Dynamics and Dispersal:

Mainly spread by intentional planting.

Origin and History:

Native to New South Wales and Queensland in Australia

Distribution:

NSW, QLD, TAS, VIC.

Macadamia integrifolia
Courtesy Australia's Virtual Herbarium.


Macadamia tetraphylla
Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate.
Prefers 1,000-2,000 mm annual rainfall areas.
Prefers Temperatures greater than 100C. Once established, they can withstand light frosts. The optimum temperature is about 250C.

Soil:

Prefer fertile, well-drained soils.

Plant Associations:


Significance:

Beneficial:

Used for commercial nut production. 211,000 tons produced worldwide in 2018.
Australia produces 40,000 ton/year in 2018.
Each tree can produce up to 18 kg of fruit.
Ornamental tree with glossy foliage.

Detrimental:


Toxicity:

Toxic to dogs.

Symptoms:

In dogs, ingestion may result in macadamia toxicity marked by weakness and hind limb paralysis with the inability to stand, occurring within 12 hours of ingestion. Depending on the quantity ingested and size of the dog, symptoms may also include muscle tremors, joint pain, and severe abdominal pain.

Treatment:

For high doses of toxin, opiate medication may be required for symptom relief until the toxic effects diminish, with full recovery usually within 24 to 48 hours.

Legislation:

None

Management and Control:

Manual removal.

Thresholds:


Eradication strategies:

Manual removal.

Herbicide resistance:

None reported.

Biological Control:

The caterpillars of some Lepidoptera feed on the leaves.
Roots are affected by Phytophthora.

Related plants:

Macadamia jansenii produces poisonous nuts containing toxic amounts of cyanogenic glycosides
Macadamia ternifolia is also used for nut production.

Plants of similar appearance:


References:

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P65-66. Diagrams.

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.