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Permanent Link: http://ufdc.ufl.edu/IR00003392/00001
 Material Information
Title: The Macadamia
Physical Description: Fact Sheet
Creator: Malo, S.E.
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
 Notes
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status: Published
General Note: "Original publication date April 1994. Reviewed November 2005 and November 2009."
General Note: "FC9"
 Record Information
Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00003392:00001


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S. E. Malo and C. W. Campbell2 1. This document is FC9, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date April 1994. Reviewed November 2005 and November 2009. Visit the EDIS Web Site at http://edis.ifas.ufl.edu. 2. S.E. Malo, Former Research Horticulturist, Tropical Research and Education Center; C.W. Campbell, Emeritus Extension Horticulturist, Tropical Research and Education Center, Homestead, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611. Reviewed by Dr. Jonathan H. Crane, Professor and Tropical Fruit Crop Specialist, Department of Horticultural Sciences, Tropical Research and Education Center, Homestead, FL Scientific Name: Macadamia integrifolia Maiden and Betche, and M. tetraphylla L.S. Origin: Australia Relatively new to world horticulture, the macadamia was discovered and described from eastern Australia in 1858 and first introduced to Hawaii in 1881. It is known today in many tropical and subtropical countries, but grown on a large scale only in Hawaii and Australia, where it has been carefully selected and improved to its present horticulturally refined status. Commercially, only M. integrifolia and M. tetraphylla and their hybrids are important. They are very similar to each other and botanically very closely related to a third species, M. ternifolia F. Muell., which produces a small, bitter kernel unsuitable as a table nut. M. integrifolia is commonly referred to as the "smooth shell" species. The fruit consists of a white kernel, high in oil content (72% oil and 4% sugar when dry), very uniform, and of excellent quality. It is enclosed in a round, hard shell about 1 inch (2.5 cm) in diameter surrounded by a smooth, bright green pericarp (husk). The leaves are stiff, oblong to lanceolate, 4-10 inches (10-25 cm) long in nodal whorls of three, rarely four, and either light green or bronze when young. The small, perfect white flowers are borne in racemes 4-8 inches (10-20 cm) long. Only a few flowers in a raceme will set fruit. M. tetraphylla is called the "rough shelled" species because of the pebbliness of the shell's surface. The husk is somewhat spindle-shaped, grayish green, and covered with a dense, white pubescence. Kernels have a grayish base, are darker in color and more variable in quality than those of M. integrifolia. The oil content averages 67% in the dry nut, with 6% to 8% sugar. The leaves are characteristically sessile and serrated along the margins, in whorls of four at the nodes. The flowers are pink and in racemes 6-18 inches (15-45 cm) long.

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The Macadamia 2 Cultivars which are hybrids of the two species possess characteristics of both, and the quality of their nuts compares favorably with that of M. integrifolia. The trees of both species are tall and spreading, reaching 60 feet (20 m) or more in height. The wood is hard and brittle. Exposed bark sunscalds very easily. There are approximately 40 described cultivars, most of them in Australia. The following varieties have been used for commercial plantings in Hawaii: `Keauhou', `Ikaika', `Kakea' and `Keaau'. `Kakea', however, is no longer propagated for commercial use. In California, `Elimba', a M. tetraphylla cultivar, is also considered of commercial value. `Beaumont', a productive hybrid cultivar is also recommended for home plantings. With good care, cultivars of M. integrifolia begin producing 5 years after planting, but appreciable yields are obtained only after the 8th year. A productive variety will bear as many as 150 lbs. of in-shell nuts per tree. Before attempting large scale plantings, cultivars should be tested locally. In Hawaii, M. integrifolia cultivars are more productive on M. tetraphylla rootstocks in soils where they are not likely to suffer from iron deficiency. Where this deficiency may be a problem, M. integrifolia seedlings should be used as a rootstock. The season of production in Florida for M. integrifolia runs from July through November. Very few commercial cultivars have been tested in this state, and more information is needed to make specific recommendations. Macadamias are relatively easy to propagate by grafting if a few simple techniques are followed. A very essential step towards success is obtaining scions 1/2 to 3/4 inch (1.5-2 cm) in diameter, from branches girdled 6 to 8 weeks previously. Vigorous rootstocks 12-18 months old are recommended, and both side veneer or side wedge grafts are used successfully. Topworking is feasible, practical, and can be accomplished by either cleft or bark grafting. Macadamias are well adapted to warm, subtropical conditions. Mature trees can withstand winter temperatures of as low as 25-26F (3-5C) for short periods with minor damage to the foliage. However, young trees and foliage are very tender and are killed by temperatures very near freezing. Temperatures below 28F (-2C) cause damage to flowers and young fruit and reduce production. In the tropics, macadamias are better adapted to medium elevations of 2100 to 3600 feet (700 to 1200 m), but in Hawaii, macadamias are not planted commercially above 2500 feet (800 m). Although the plant is quite resistant to drought, supplemental irrigation is very important, particularly during the flowering and fruit setting season. Severe moisture stress results in considerable drop of young fruit. Macadamias are not demanding for soil fertility, but they do require good drainage. They need relatively higher amounts of phosphorous in the fertilizer than other fruit crops, particularly when the trees are young. A N P2O5 K2O ratio of 2:4.5:2 (10-22.5-10) has given good results in the lava soils of Hawaii. In the calcareous soils of south Florida, they are likely to suffer from zinc, manganese, and iron deficiencies. Nutritional sprays will control the first two. However, iron chlorosis is only corrected by soil applications of chelates especially formulated for these soils. Leaves are occasionally infested by thrips and mites, which may become serious in large plantings. Green stinkbugs cause considerable damage at times by injuring very young fruit when the shell is still soft. Rats, squirrels, and nut borers also cause substantial losses if unchecked. Anthracnose (Colletotrichum spp.) attacks leaves and the husks of immature nuts. Diseased nuts do not drop when mature and usually spoil while still attached. Phytophthora cinnamoni, which causes root-rot in avocados, produces a trunk canker in macadamia which may kill young seedlings. Fortunately, the tree

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The Macadamia 3 is quite resistant to the root rot caused by this fungus. Mature nuts fall to the ground and have to be gathered manually every week to prevent spoilage, particularly from moulds. Husking is done soon after harvesting and before the nuts are mechanically cracked. They are air dried at temperatures not higher than 110F. The moisture content of the kernel is reduced to less than 1.5% to prevent development of off-flavors after roasting (either dry roasting or in a refined coconut oil at 275F for 12 to 15 minutes). Macadamias are considered to be one of the finest table nuts of commerce. At present, they command premium prices because the demand far surpasses current production. They are ordinarily offered on the gourmet shelves of supermarkets as salted nuts packed in glass jars. The largest use, however, is in confections. Only whole nuts are packed in jars.