The Australian Introductions

The Australian Introductions

 

C. A. Schroeder and B. P. Frolich*

Reprint From CMS 1960

The selection of Macadamia varieties in Hawaii during the period 1930 to 1940 was made primarily among seedlings of the species now called Macadamia integrifolia, commonly known as the smooth leaf, smooth shell Macadamia. The early introduction of Macadamia into Hawaii as a reforestation tree was by seed. The large integrifolia seedling population available when the Hawaiian Experiment Station began its search for improved varieties naturally resulted in the selection of integrifolia types, which have proved exceedingly well adapted to the environmental conditions of the Islands. Very little attention was given to the M. tetraphyllaseedlings in Hawaii because of the limited numbers, which were found there. Most of these tetraphylla seedlings probably resulted from a single introduction or at the most a few early introductions from apparently inferior seed sources. It is now known that seed sources giving seedling types of M. tetraphylla superior to those in Hawaii are accessible in Australia. Seed from these new sources and new clonal tetraphylla materials arc now being tested and evaluated in light of the early experience with the better known integrifolia types in Hawaii.

The recognition by the Australians of the potentialities of Macadamia as a crop plant and the stimulation provided by the researches in Hawaii have resulted in considerable seedling selection work in Queensland among some of the native Macadamia populations, which are endemic there. These investigations conducted by the Queensland Department of Agriculture resulted in the selection and testing of a number of clones, mostly of the tetraphylla type, which proved most suitable for quality production and yield under their conditions. The more promising of these selections were announced about 1951 and attracted attention both in Hawaii and California at that time.

The enthusiasm, optimism, and genuine curiosity concerning the Macadamia nut by Col. Wells W. Miller resulted in his participation in the founding, guidance, and eventual presidency of the California Macadamia Society. This interest in a potential commercial fruit or nut industry for California again was evident by Colonel Miller’s extensive inquiries at all sources for information on the Macadamia and its adaptability to California conditions. Much personal effort, energy, and time were involved in these early inquiries. One of these quests for knowledge by Col. Miller was made in the spring of 1951 while on a military assignment in eastern United States. While in the vicinity of Washington, D.C., he visited the U. S. Department of Agriculture Plant Industry Station at Beltsville. Here as the result of previous correspondence he met Dr. W. E. Whitehouse, who was responsible for the Federal plant introduction program. Dr. Whitehouse, upon hearing of the interest in the Macadamia in California, was quite receptive to the idea of attempting to import into the United States some of the seedling selections which had just been announced by the Federal Department of Agriculture and Stock, in Queensland, Australia. Through the convincing efforts of Col. Miller, Dr. Whitehouse made contacts with the Australian governmental agency and arranged to have scionwood of the best six or eight selections sent directly to the University of California at Los Angeles for establishment and testing in comparison with other varieties of the then largest Macadamia variety collection in California. The scions were received as grafting pieces in 1952. There were two different shipments. The first shipment consisted of F 1 and H 3, the second of J 3, J 4, and J 6. No materials of the clone D-1 were received. The scions were top worked on seedlings in the orchard at UCLA.The data and description of these clones provided by the horticulturists from Australia and which accompanied the scions indicated very interesting and highly promising characteristics in the varieties. Among these original descriptions excerpts are as follows:

J 6—An excellent thin shelled variety— 48percent kernel separating freely from the shell. A desirable nut for table use. Tree is open and spreading but has been a shy bearer.

F 1—A smooth, mottled, thin shelled variety with good kernel size and color yielding 50 percent kernel. The thin shell should make an excellent table nut and large size would make it favorable for processing. Thc tree is dense and may require regular pruning to keep the center open. It has pink flowers, is a prolific hearer and matures fruit early in the season.

J 4—A large thin-shelled nut with desirable kernel size, shape and color. It separates well from shell. The crack-out is 45 percent. The tree is open, spreading, round type, well furnished with laterals. It hears heavily. Occasionally twinning of nuts is observed.

J 3—An excellent thin-shelled nut similar to J 4 but slightly smaller. It yields 47% kernel but exhibits considerable incidence of insect and mould damage. The tree is tall with very spiny leaves, of open growth habit with fruit borne toward the center. It is a moderate bearer of fruit early in the season.

H 3—A comparatively large, thin shelled nut with a yield of 41 percent. The kernel is of desirable size and leaves the shell freely. The tree has pink flowers, upright growth. It is a consistent heavy hearer of early season fruit. There is some tendency toward germination of the embryo in the pericarp, especially during wet weather.

D 1—An extremely thin shelled nut yielding 54 percent kernel which separates cleanly from the shell. The kernel is of desirable size. The color and texture are good but on cooking the flavor becomes slightly defective. The leaves are spiny. The seed were originally obtained from Mr. W. B. Petrie of Petrie.

 

The extensive exploration of Macadamia areas of Australia in 1954 by the late Dr. J. H. Beaumont of Hawaii brought to light many selections of the prickly leaf, rough shell tetraphylla types, which may have considerable promise both in Hawaii and California. While some of Dr. Beaumont’s selections have also been introduced into California by Dr. W. B. Storey of the Citrus Experiment Station, it is as yet too early to evaluate their behavior or potentiality.

The Macadamia forms, which were introduced into California prior to 1900 and shortly thereafter were seedlings mostly of the tetraphylla or prickly leaf type. Some introductions, however, were of the smooth leaf integrifolia type. A number of the predominating tetraphylla type trees have been observed over the years to bear nuts of good quality and in moderate quantity. Hence there is some reason to anticipate that the tetraphylla type Macadamia is fairly well adapted to California conditions and could provide among its progeny clones of acceptable commercial quality and yield. The recent introductions from Australia of the tetraphylla type therefore should prove of considerable interest and can be given fair trial under our conditions, where they may indeed be of greater value than the integrifolia types now on trial from Hawaii. Only after several years can we really evaluate any of these introductions.

The observations made in California on the behavior of the older Australian clones thus far are limited in number and extent but are nevertheless encouraging and favorable in respect to some of the clones. The oldest of the materials at UCLA have been markedly retarded in their development and modified in behavior by the extensive and severe cutting of scionwood for propagating purposes, hence these notes cannot truly indicate the real flowering or bearing habit of the trees. Marked differences between clones in general growth habits are evident.

The clone H 3 at UCLA is a dense grower with heavy textured, large leaves. The bloom is borne in profusion on both old and new wood. It is precocious and bears large, thin-shelled nuts somewhat earlier in the season than other clones. Propagation appears to be somewhat more difficult to judge by the poorer graft takes and lesser percentage rooting of cuttings as compared to the other Australian selections. There is some possibility that this clone may have been mislabeled or otherwise confused in identity with that of the true Australian F 1, which was received in the same shipment.

Clone J 3 is a typical tetraphylla type having a dark green prickly leaf. It is a vigorous grower but has produced no fruit yet.

Another vigorous tetraphylla clone is J 4It has large prickly leaves having a distinctive yellowish color highly suggestive of a mild nitrogen deficiency characterize this clone. Other clones on adjacent limbs of the same tree, however, arc deep green, hence there is little probability that nitrogen in the soil is a limiting factor. The clone J 4 has proved somewhat difficult to propagate by grafting. Currently it has a good bloom.

The selection J 6, highly rated by the Australians, suffered severe damage in a windstorm, which snapped the 2-inch trunk, hence the clone has been repropagated.

One clone, F I of the Australian selections, is markedly different in its red coloration of the new growth. It is exceptionally easy to propagate. Rooted cuttings appear to grow as vigorously as seedlings. Crafting likewise is highly successful. The general open type of growth observed at UCLA differs from that described as "dense" by the Australian literature, hence we believe that this clone too possibly was mislabeled. The clone F 1 at UCLA appears more like the described clone H 3. Clone F I currently have a profusion of pink flowers.

A limited number of reports from growers who have grafted the Australian materials from UCLA indicate these clones are in general quite vigorous and somewhat precocious in respect to production of flowers. None has borne fruit in sufficient quantity to appraise its quality.

 

*Dr Schroeder is Associate Professor, Mr. Frolich is Laboratory Technician, Department of Subtropical Horticulture, University of California at Los Angeles