Macadamia Nut

タイトルまたは説明

Common Names:Macadamia, Australian nut, Queensland Nut.

 Species: "Smooth-shelled Macadamia" (Macadamia integrifolia Maiden & Betche), "Rough-shelled Macadamia" (M. tetraphylla L. Johnson). Hybrid forms exist between the two species.

Distant Affinity: Helicia nut (Athertonia diversifolia), Chilean Hazel (Gevuina avellana), Australian Rosenut (Hicksbeachia pinnatifolia).

 Growth Habit: Macadamias are large, spreading evergreen trees reaching *0 to *0 ft. high and almost as wide. More upright types are known and being selected because of their suitability for closer planting. The bark is rough but unfurrowed, brown and dark red when cut. The macadamia has proteoid roots, dense clusters of short lateral rootlets in well defined rows around the parent root axis. The prime function of such roots appears to be in increasing the surface area of the root system for maximum absorption. The vigor of seedlings appears to be related to the degree of proteoid root development.

 Foliage: The two species are fairly easily distinguished by their foliage. The leaves of M. integrifolia are 8 to *1 inches in length and occur usually in whorls of 3. The adult leaves are entire with few spines. New growth is pale green. The spiny, often sessile leaves of M. tetraphylla usually appear in whorls of 4 and may grow to *0 inches long. The new growth is bronzy pink. Growth in mature trees of both species occurs in two flushes, in spring and midsummer. In young trees four flushes may occur.

 Flowers: Flowers are borne on long narrow racemes arising from the axils of leaves or the scars of fallen leaves. They may be borne on the new growth if it is mature, but more often on the two, or three season's growth preceding the most recently matured flushes. The flowers, about 1/2 inch long, are perfect but incomplete in that they have no petals, but four petaloid sepals. M. integrifolia has creamy white flowers borne in clusters 6 to *2 inches long, while the flowers of M. tetraphylla are cream-colored or pink and borne in clusters up to *5 inches long. Macadamias can self-pollinate, although varieties vary from being totally self-compatible to being almost self-sterile. Wind pollination may play some role, but bees are apparently the major agent in pollination. Cross-pollination by hand has been shown to increase nut set and quality.

 Fruit: Macadamia nuts have a very hard seed coat enclosed in a green husk that splits open as the nut matures. As the common name indicates, this seed coat is smooth in the case of M. integrifolia. It holds a creamy white kernel containing up to *0% oil and 4% sugar. When roasted it develops a uniform color and texture. Although M. tetraphylla is often referred to as the rough-shelled macadamia, the seed coat of some cultivars are smooth, while others are rough and pebbled. The quality of the kernels of M. tetraphylla are also more variable. The oil content ranges from *5% to *5% and sugar content ranges from 6% to 8%. These factors result in variable color and texture when the the nuts are roasted under the same conditions as those of M. integrifolia. 

 Harvest: Harvested nuts are dehusked and spread in a dry place protected from the sun and allowed to dry for 2 or 3 weeks. To finish drying the nuts are placed in a shallow pan and placed in the oven at the lowest temperature setting (**0° to **5° F) for about *2 hours wher they are stirred occasionally to ensure that the nuts do not cook. The nutsare then stored in a cool, dry area.When the nuts are dry, the shells can be removed with a nutcracker.