Data from two trees each of ‘Keauhou’, also known as 246, were collected in 1968 from 20 different locations in Hawaii on three different sampling dates and compiled and analyzed by Radspinner. These samples gave an average kernel percentage of 38.8 and 85.1 percent of No. 1 kernels. No. 1 kernels are those, which float in water because of their relatively high oil content. An average percentage of kernel to ‘nut by weight, of 38.8 percent, is quite satisfactory but 85.1 percent of No. 1 kernels is rather disappointing compared to some oilier cultivars. ‘Keaau', ‘Kakea’ and ‘Kau,’ for example, are well-known cultivars, which usually average more than 90 percent of No. 1 kernels.

According to Table 1, the variation in kernel quality of ‘Keauhou’ in 1968 ranged from 60 to 98.8 percent, depending upon location. There is no readily apparent reason for this wide range of variation and no definite explanation can be offered at this time. A similar situation was found in 23 samples of ‘Keauhou’ collected and analyzed over a 38-year period from 1936 to 1975. The range in these samples is from 57 to 98 percent with an average of 84.9 percent of No. 1 kernels. This agrees well with 85.1 percent for the samples collected in 1968 by Radspinner.

These average percentages of No. 1 kernels shown in Table 1 are in close agreement and there is no indication of important or significant differences between the 1968 samples and those compiled from 1936 to 1975. Agreement in average percent kernel is also very close, with 38.8 for Radspinner’s 1968 data, compared to 39.5 for 23 samples taken during the period from 1936 to 1975. Again, there is no suggestion of a significant difference between these averages.

It is therefore suggested that because of close agreement in the two sets of data, the 1968 sampling of ‘Keauhou’ by Radspinner gave a reliable evaluation of both kernel quality and percent kernel in this variety.s

The range of variation in both kernel percentage and percent of No. 1 kernels is also important in that it provides a measure of variability from location to location and from year to year. The range of variation in percent of No. 1 kernels for both sets of data is approximately 40 percent. Percentage of No. 1 kernels in 9 of the 43 samples tested was 75 percent or less. Since No. 1 kernels are measured by specific gravity by floating them in water, it is evident that the oil content of ‘Keauhou’ is sometimes unsatisfactory.

Present selection standards for new varieties have been set at a minimum of 95 percent of No. 1 kernels. This is considerably higher than 85 percent, which is about average for ‘Keauhou.’ Higher selection standards for kernel quality in new varieties should eventually result in only about 1/3 as many off-grade kernels as ‘Keauhou.’

Quality, which is closely correlated with high oil content, was not as critically considered earlier in the selection program when the first cultivars were named, as it is at the present time, it is now considered of paramount importance, since off-grade kernels with less than about 70 percent oil have relatively low salvage value. These are the kernels, which usually turn brown when they are processed.

The average percent kernel of 39.1 found for ‘Keauhou’ is quite satisfactory but the range of about 28 percent is surprisingly large. This suggests that ‘Keauhou’ is somewhat variable in both kernel quality and percent kernel. This confirms a fact, which has become fairly well known by Macadamia growers and processors through experience. This is the fact that ‘Keauhou’ is a very good variety in Hawaii during years when there are optimum growing conditions. In less favorable locations, however, other cultivars such as ‘Kau,’ ‘Kakea’ and ‘Keaau’ often perform better than ‘Keauhou’ and may therefore be preferable for new plantings. ‘Keauhou’ however, still remains an excellent variety in areas where growing conditions are optimum or near optimum. These conditions include fertile, well-drained soil, good wind protection, elevations between 500 and 1500 feet and a minimum of about 60 inches of annual rainfall well distributed throughout the year.

Table 1.Percent kernel recovery and grade 1 kernels (floaters)

of ‘Keauhou’ from 1936 to 1974 and in 1968.