Objective  Phenotypic diversity of inflorescence from a collection of 40 Macadamia spp. was determined to evaluate and better utilize the resources.

  Method  Using the “Standards for Description and Data Analysis on Macadamia” and the “Techniques and Codes for Evaluating Macadamia Germplasms” as references, this study was conducted. Data were subjected to cluster and principal component analyses.

  Result  The inflorescence characteristics of the plants showed that 90% of the germplasms had creamy white flowerets, 50% of the flowerets opened sequentially from the base to the top of inflorescence axis, and 77.5% of them did not flower in batch. The maximum coefficient of variation on inflorescence length was 26.30%, and the minimum 8.60%. The cluster analysis based on 6 phenotypic characteristics of the inflorescence divided the 40 germplasms into two groups at an euclidean distance of 4.79. The categorization was mostly determined by the inflorescence length and floweret count. The 6 phenotypic characteristics composed of 3 independent principal components (i.e., floweret count, floweret color, and flowering sequence) constituting 71.752% of the total variance, The principal component analysis directly demonstrated the phenotypic characteristics of inflorescence which basically agreed with the results obtained by the cluster analysis.

  Conclusion  The phenotypic diversity of macadamia inflorescence was abundant among the germplasms. The inflorescence length, floweret count, floweret color, and opening order of floweret were the dominant factors constituted to the diversity on the inflorescence.