Origin
Macadamia tetraphylla L.A.S.Johnson, also known as the rough-shelled macadamia, is a species of flowering tree that belongs to the family Proteaceae. It is native to the rainforests of southeastern Queensland and northeastern New South Wales in Australia.
Common Names
In addition to being called rough-shelled macadamia, this species is also commonly known as the 'prickly macadamia', 'Australian nut', 'bauple nut', or 'queen of nuts'.
Uses
Macadamia tetraphylla is highly valued for its edible nuts which are used in the culinary industry, particularly in confectionery and baking. The wood of the tree is also used in the manufacture of furniture, flooring, and veneers, while the oil derived from the nuts is used in cosmetics, skin care products, and as a cooking oil.
General Appearance
The rough-shelled macadamia is a medium-sized tree that grows up to 15 meters tall and has a dense, rounded crown. It has dark green leaves that are arranged in whorls of four, giving the species its name 'tetraphylla'. The tree produces clusters of cream-colored flowers that give way to woody, rough-husked nuts that are spherical in shape and contain a hard-shelled seed inside. The foliage and flowers of the Macadamia tetraphylla are an attractive feature, making it a popular garden and landscape tree in many parts of the world.
Light Requirements
The Macadamia tetraphylla plant requires full sun exposure to thrive. Therefore, it is best to plant it in an open area or away from tall trees that could provide shade. In areas with extreme heat, the plant can tolerate some shade during the hottest parts of the day.
Temperature Requirements
The Macadamia tetraphylla plant can thrive in warm to hot temperatures. It grows well in areas with temperatures ranging from 20-30°C (68-86°F). However, the plant is susceptible to frost damage and cannot tolerate temperatures below -1.1°C (30°F).
Soil Requirements
The Macadamia tetraphylla plant grows best in well-drained soils with a pH range of 5.5-6.5. The ideal soil should be rich in nutrients and organic matter. The plant does not do well in heavy clay soils or soils that are prone to waterlogging. It is recommended to add compost or organic matter to the soil before planting to improve soil structure and fertility.
Cultivation methods
Macadamia tetraphylla is a tree that can attain a height of up to 15 meters and a spread of 10 meters. It is propagated by seed or grafting and requires full sunlight to grow and produce fruit. The plant thrives in well-drained soils with a pH range of 5-6.5 and moderate rainfall, ideally between 1000-1500mm per annum.
Water needs
During the establishment phase, Macadamia tetraphylla requires frequent watering, especially during the dry season, to encourage root development. However, mature trees are drought-tolerant and only require regular watering during prolonged dry spells.
Fertilization
The plant requires regular fertilization to ensure optimal growth and productivity. Application of well-balanced fertilizers with trace minerals should be done in accordance with the manufacturer's instructions. Nitrogen, phosphorus, and potassium should be provided in a ratio of 12:4:8, respectively, to promote healthy growth. Fertilizer application should be done in spring as the plant starts actively growing and after the production season to replenish soil nutrients.
Pruning
Pruning is an essential aspect of Macadamia tetraphylla cultivation. Trees should be pruned to maintain an open canopy, allowing adequate sunlight penetration and air circulation, which reduces pest and disease incidence. Pruning should be done during the early stages of growth to aid development and periodically during the production phase to promote yield and increase fruit quality. It is advisable to engage a professional pruner for large-scale operations to ensure proper technique and prevent damage to trees.
Propagation of Macadamia Tetraphylla
Macadamia tetraphylla L.A.S.Johnson, is commonly known as the tetraphylla macadamia nut or the rough-shelled macadamia nut. The plant is native to southeastern Queensland in Australia and is now cultivated worldwide due to its edible nuts. Propagation of Macadamia tetraphylla can be done by various methods including:
Seed Propagation
Propagation through seeds is the most common method of propagating macadamia nuts. The best time to sow the seeds is during spring or summer when temperatures are between 25 to 30 degrees Celsius. The seeds should be collected from healthy mature trees and sowed immediately as they have a short viability period of a few weeks.
The seeds should be sown in well-drained soil that is rich in organic matter. The depth of sowing should be about twice the size of the seed. The seeds should be watered evenly and kept moist until germination which takes about 6 to 8 weeks.
After germination, the seedlings should be transplanted to larger containers and then onto the field once they are about 30 cm high.
Grafting
Grafting is another method of propagating macadamia nuts. The method involves joining a scion of a desirable variety to a rootstock of another variety. This method is used to maintain the characteristics of a particular variety of macadamia nut.
The best time to graft is during winter when the plants are dormant. The scion should be obtained from a mature tree, and the rootstock should be obtained from a seedling. The scion and rootstock should be of the same diameter, and the graft union should be made in such a way that the cambium layers of both the scion and rootstock are in contact.
The grafted plant should be protected from strong sunlight and wind until it establishes. After establishment, the grafted plant can be transplanted to the field.
Layering
Layering is another method of propagating macadamia nuts. The method involves bending a low-lying branch to the ground and covering it with soil. The covered part of the branch will produce roots, and a new plant will develop. Layering is a slow method of propagation, and it can take up to two years for a new plant to develop.
These are the major methods of propagating Macadamia tetraphylla. Each method has its benefits and drawbacks, and the choice of method depends on the desired outcome and the available resources.
Disease and Pest Management for Macadamia tetraphylla L.A.S.Johnson
Macadamia tetraphylla L.A.S.Johnson, also known as the rough-shelled macadamia, is a plant species that belongs to the family Proteaceae. It is mainly grown for its edible nuts and is native to southeastern Queensland and northeastern New South Wales in Australia. Like any crop, it is susceptible to various pests and diseases that can cause a range of damages. Therefore, it is essential to understand the common diseases and pests that might affect the plant and suggest ways to manage them.
Common Diseases
Phytophthora root rot: This is a severe fungal disease that affects many plant species, including Macadamia tetraphylla. It is caused by the soil-borne pathogen, Phytophthora cinnamomi, and can lead to tree decline and death. The fungus attacks the roots and spreads to the trunk, causing cankers and lesions. The best management strategy is to avoid planting in poorly drained soils and to use planting materials that are not infected with the pathogen. Other practices include proper irrigation and drainage, application of fungicides, and removal of infected trees.
Macadamia kernel rot: This is a fungal disease that affects the nuts and can cause significant yield losses. It is caused by the pathogens Botryosphaeria dothidea and Lasiodiplodia theobromae, which infect the nuts through wounds or cracks. The infected nuts become discolored, and the kernels turn dark brown or black. To manage this disease, it is crucial to avoid mechanical damage to the nuts during harvesting and processing, and to control insect pests that can cause physical injuries. Fungicides can also be applied during nut development to reduce infection.
Common Pests
Nut borer: The nut borer, also known as banana stalk borer or Macadamia twig girdler, is a significant pest of Macadamia tetraphylla. The larvae of these moths bore into the nuts, causing them to fall prematurely. The adult moths also damage the trees by girdling the twigs and branches. To manage this pest, it is vital to prune and remove infested twigs and branches, use pheromone traps to monitor and control the population, and apply insecticides to target the larvae.
Mistletoe: Mistletoe is a parasitic plant that can cause significant damage to Macadamia tetraphylla and reduce its growth and yield. It is spread by birds and seeds, and once it attaches to the tree, it draws nutrients and water from the host plant. The best management strategy is to prune and remove the infected branches or stems before the mistletoe matures and produces seeds. Chemical treatment with herbicides can also be used, but it requires expertise and caution.
Scale insects: Scale insects are small, sap-sucking pests that can damage the foliage and fruits of Macadamia tetraphylla. They secrete a sticky substance called honeydew, which can attract ants and sooty mold. The best management practices include regular monitoring and early detection, removal of infested branches or fruits, and application of insecticides or horticultural oils to kill the insects and their eggs.
In conclusion, Macadamia tetraphylla L.A.S.Johnson is susceptible to various diseases and pests that can lead to yield losses and reduce the quality of the nuts. Therefore, it is crucial to implement effective management strategies to control and prevent the spread of these problems. A combination of cultural practices, monitoring, and chemical treatments can be used to manage these issues, but caution and expertise are needed to ensure the safety and efficacy of the treatments.
