NEW MACADAMIAS NEED GOOD LOCATION

R. A. Hamilton*

Reprint from CMS 1959

The land on which a new Macadamia orchard is located represents a long-time investment. The profitable life of these nut orchards in Hawaii has not been fully determined. However, orchards about 20 years old are among the most productive known.

With good soil, favorable climate, and suitable soil moisture conditions, the trees appear capable of producing satisfactory crops for at least 40 to 60 years. Older, larger trees cause no problem if they are spaced far enough apart to prevent crowding. Since the nuts are harvested after they fall to the ground, it is no more difficult to pick them up under a tree 50 feet high than one 5 feet high. Healthy, well-grown trees increase in productivity, as they grow older and bigger.

Macadamia orchards cannot be expected to show much profit for at least 10 years after transplanting. Yields will be low, and transplanting and other expenses will be relatively high. However, after that period, the income from well-managed orchards on good sites should increase.

Good sites are of prime importance. In the past, much of the land planted to Macadamia trees was not suited to producing nuts economically. The trees were usually planted on poor land not suitable for cane or pineapples. The fact that the trees were even able to exist on some of these shallow soils and windswept locations testifies to their adaptability and hardiness under adverse conditions.

Some of the most important factors to be considered in deciding on the best available location for a new orchard are (1) soil, (2) natural wind protection, (3) elevation, (4) rainfall, and (5) ease of harvesting.

Good Soil a Must

There is certainly no factor of greater importance in an orchard than the soil. An ideal Macadamia soil is a reasonably fertile loam soil permitting good root growth to a depth of at least 3 feet, with adequate under-drainage and a moderately high organic matter content. Practically all soils in Hawaii suitable for orchards will need applications of fertilizer, the amount and type depending on the character of the soils and the size of the trees.

It is strongly recommended that, when starting a new orchard, every effort be made to secure the best technical information available from persons specially trained in soil analysis who have a knowledge of the requirements of Macadamia trees. A representative sample of soil down to a depth of at least 3 feet should be examined and an accurate chemical analysis made, including tests for manganese.

The high manganese soils, commonly known as "red soils", are often not suitable for Macadamia growing. The trees may develop characteristic yellowed-leaf patterns and may be lacking in productiveness and vigor. Where high manganese symptoms are found in Macadamia, they arc usually more severe in dry weather than during the rainy season.

In some instances, growth of young trees on high manganese soils is apparently satisfactory. Factors such as depth of topsoil and hardpans undoubtedly influence tree growth on red soils. A qualified soil specialist should be consulted before an attempt is made to grow Macadamia trees on high manganese soils.

Although the soil acidity or pH range most favorable to the growth of Macadamia trees has not been definitely determined, a pH range of 4.5 to 6.5 is considered favorable for Macadamia trees in Hawaii.

Wind Protection Important

It is difficult to over emphasize the importance of securing the best possible natural wind protection for new Macadamia orchards. Many Macadamia trees, grown on exposed locations, have been lost or damaged from the wind. Even trees in relatively sheltered areas are sometimes injured by occasional heavy winds, particularly Kona winds.

Trees exposed to steady trade winds also present a problem. They continue to grow, but they lean away from the winds at an angle and do not produce a satisfactory crop of nuts.

Take advantage of hollows, sheltered slopes, and valleys in considering an orchard location. Avoid windswept slopes and exposed areas. However, if trees are planted in areas exposed to steady trade winds, a well-planned system of windbreaks will be necessary.

Influence of Elevation

Macadamias grow well in Hawaii at elevations ranging from near sea level up to about 2,500 feet. The amount and distribution of rainfall are often limiting factors at low elevations. Supplementary irrigation is of course possible, but, at this time, there is not enough information available about irrigation of macadamias to make definite recommendations.

It is well established that the shells of the named varieties of nuts become appreciably thicker at elevations above 2,000 feet. However, there is little difference between the sizes of kernels from nuts of the same variety grown at different elevations.

The annual rainfall, in sections of Hawaii where Macadamia nuts grow best, ranges from 50 to 150 inches. The average annual rainfall is not as important to the trees as are the distribution of rainfall, the depth of rooting, and the type of soil. Once the trees have become established, they will survive considerable periods of drought. However, although trees planted in low rainfall areas may survive, they cannot be depended on to bear good crops. In this respect, low humidity and insufficient soil moisture are also hazards when transplanting young trees.

Harvesting a Consideration

A final consideration in planting a new orchard is the harvesting in later years. The location should allow construction of roads into the orchard at a reasonable cost. Macadamia nuts fall to the ground when mature and are picked up and sacked by hand. Because of this, space under the branches must be cleared of weed growth and leveled to facilitate picking the nuts off the ground. It is apparent that on excessively steep slopes, or on land that is extremely rough and rocky, the cost of building a road and of clearing and leveling space under the trees would be prohibitive. All the factors discussed should be considered carefully before planting a new orchard.

*Dr Hamilton is an Assistant Horticulturist, HAES, College of Agriculture, University of Hawaii.

Reprint from Hawaii Farm Science, October, 1953, by permission of University of Hawaii.