Reprint CMS 1968

Publication of the article reproduced below in Science in 1937 proved to be an important milestone along the path of progress in the domestication and development of the Macadamia from a newly discovered Australian forest tree just 100 years ago to an increasingly important orchard crop tree in the tropical and subtropical regions of the world.

OCTOBER 1,1937 Science 137

The most satisfactory method of propagating many woody plants vegetatively is by grafting. In temperate regions, grafting is usually done in the late winter or early spring when the plant has passed through a dormant period, is well stocked with food reserves, and the plant is ready to make its annual increment of growth. In Hawaii, however, there is no apparent dormant season in the litchi and little consequent accumulation of reserves. Starch, the principal carbohydrate storage form in the litchi, rarely accumulates too greater when .4 to .5 per cent of the dry weight of non-flowering branches. The small amounts that do accumulate are quickly italicized in making a new flush of growth.

The usual method of propagating the litchi in China is by means of air layering, which may be considered a form of cuttage. The treatment, i. e., the removal of a ring of bark, is such that carbohydrates accumulate and roots are produced in a suitable container before removal from the tree. Mitchell and Reid have shown the importance of carbohydrates in the rooting of tomato cuttings, while little attention has been given to their importance in vegetative propagation by grafting. For many years, attempts have been made to graft the litchi, without regard to the carbohydrate storage, with very little success. By using scions high in starch we have increased the percentage of successful grafts from 10 per cent, as reported by Pope to 75 and 80 per cent. Carbohydrates are caused to accumulate in the scion by removing a small ring of bark about one eighth inch wide from the branch, to be used three to four weeks later as Scionwood. This branch should be about one to three fourth inch in diameter. Table I shows the composition of the Scionwood before and three weeks after girdling.

TABLE 1

Effect of Girdling on Carbohydrate Accumulation in Litchi (Litchi Chinensis)

Agricultural Experiment Station

University of Hawaii

The Macadamia (Macadamia tetraphylla and M. integrifolia, both of which were thought to be different forms of M. ternifolia. the gympie nut or Maroochy nut until 1954) is native to the eastern coastal region of northern New South Wales and southern Queensland. The first species of Macadamia to be discovered by botanists is M. ternifolia by Ferdinand von Mueller, Royal Botanist of the Botanic Garden at Melbourne and Walter Hill, Director of the Botanic Garden at Brisbane who collected specimens on an exploration of the forests along the Pine River in southern Queensland in 1857. Mueller discovered their collection to be a new and undescribed species in the plant family Proteaceae. Furthermore, its characters did not fit it in into any known genus. Consequently, in 1858, he established the genus Macadamia, naming it in honor of Dr. John Macadam, then Secretary, and later President, of the Philosophical Institute of Victoria. He described the collection and named it M. ternifolia, establishing it as the type species for the genus.

M. tetraphylla was discovered sometime prior to 1870, although its real identity and typification were not established until done so by L. A. S. Johnson of the National Herbarium of New South Wales at Sydney in 1954. A seedling orchard was planted on the K. C. Fredrickson Estate at Rous Mill, New South Wales about 1870. This orchard still exists and continues to produce good crops of nuts.

M. integrifolia must have become known about the same time as M. ternifolia, of which it was thought to he a botanical variety. Its identity as a valid species in its own right was not recognized until 1897 when two botanists,

J. H. Maiden and E. Betche described it as a good species and published the name it now bears. Meanwhile, seeds were brought to California and trees established at the University of California at Berkeley in 1879*. W. H. Purvis, the other, made two early introductions into Hawaii, one in 1881 by R. A. and F. W. Jordan in 1895. All of the recommended commercial integrifolia varieties in Hawaii and California are descendants of the Jordan introduction.

Very early, a belief spread and became accepted that the Macadamia defied propagation by budding and grafting. Consequently, all Macadamia trees wherever planted were seedlings. By 1927, there were about 600 acres of seedling orchards in Hawaii, and 100, or possibly more, acres in Australia.

In 1927, Ralph H. Moltzou, a Honolulu high school boy who worked part time as a waterer and weeder in the nursery of the Hawaii Agricultural Experiment Station, grafted some scions to potted seedlings. His scions were taken from the branch of a tree that had been broken by the wind and had hung on by the bark and perhaps a little of the shattered wood for about three weeks before being pruned off. To his surprise, as well as the surprise of Willis T. Pope, the Horticulturist, some of the scions took and grew, and the Macadamia had been grafted successfully for the first time in history.

Follow-up experimentation demonstrated the feasibility of multiplying selected types by grafting. In the 1928 Report of the Hawaii Agricultural Experiment Station, Pope stated "___ The grafts were successful when seedling stocks nearly a year old, growing in gallon containers, were used. Side-tongue grafts and whip grafts when well made and the union, including the entire scion, coated with paraffin, succeeded with little difficulty. It is believed that this method, with possibly some improvement may be used in standardizing a good variety, which will mean much toward developing the Macadamia industry in Hawaii.

Grafted trees were produced from that time on, but the significance of the broken branch seems to have been overlooked, so the percentage of successes was small and nut to he depended on and the number of trees was small.

In January 1936, Pope retired and J. H. Beaumont succeeded him as Head of the Horticulture Department. On July 1, 1936 he added a young plant physiologist named W. W. (Bill) Jones to his staff.

From his experience with orchard crops in West Virginia, Minnesota, North Carolina, and Maryland, Beaumont was quite certain that the Macadamia could never attain importance as an orchard crop based on seedling trees, which varied so greatly in productivity, size, and quality. He immediately launched a two-phased program for Macadamia development.

One phase concerned the search for and testing of promising trees for selecting superior types for naming and introducing as commercial varieties. Success of the program depended, of course, upon developing a successful, economical means for clonal propagation. This condition was met and in 1948, twelve years after the work was initiated five varieties were introduced out of 60.000 bearing seedling trees screened. In 1952, two additional varieties were named, and in 1966 a third one was named after an additional 25,000 or more seedlings had been screened.

The other phase was concerned with the physiology of clonal propagation. As may be seen (Fig. I) it was quickly solved and the propagation bottleneck broken. As noted by Jones and Beaumont " . . . the Macadamia ... formerly was considered almost impossible to propagate by grafting." Now, it seems almost ridiculously easy, with success generally in the 95-100 per cent range. Budding is now done successfully in Costa Rica, and propagation of cuttings with the use of mature leafy terminal twigs in a propagation bed with bottom heat and an overhead misting system is quite feasible.

The experiments reported by Jones and Beaumont not only made the variety selection possible but also provided the impetus for large-scale investment and development in Hawaii. Present plantings are reported to cover about 7,000 acres, 90 per cent of which consist of grafted trees of selected varieties.

The Hawaiian success story gave a boost to Australian growers. Present acreage is reported as 8000 with 23000 in prospect. Also, tremendous interest has developed around the world, and inquiries and requests for material for a start continue to pour in from a number of nations in Africa, all of the nations of Central America and northern South America, island nations of the Caribbean region and the Pacific Ocean area, and southeastern Asia.

What now of the principals in this clonal propagation saga?

Willis T. Pope died in 1961 at the age of 78.

J. H. Beaumont died suddenly after a brief illness on July 16, 1957 at the age of 63.

Ralph Moltzou is now manager of the Libby McNeil and Libby pineapple plantations on the island of Molokai, Hawaii

Winston W. Jones is Professor of Horticulture at the University of California, Riverside. His interest in macadamias has never waned. He has had several articles in past and recent volumes of the Society’s Yearbooks and has given addresses at annual meetings. He was Major Professor on the Committee, which directed the research and preparation of the dissertation by Ian Muir Gilfillan on biochemical relationships in chlorotic Macadamia leaves, An abstract of the dissertation was published in the 1967 Yearbook.

* Professor of Horticulture, University of California, Riverside, California

* "Historical Macadamia Tree of California", California Macadamia Society Yearbook 1965—30-31.