Male and female strobilus production was assessed annually over a five-year period for a clonal seed orchard of sugi (Cryptomeria japonica D. Don) in Korea. Clonal fertility and fertility variation, expressed by both sibling coefficient and coefficient of variation in strobilus production among 40 orchard clones, were reported. Fertility varied among clones and among years, producing five-year averages per ramet of 464.3 and 971.1 for female and male strobili, respectively. The correlation between female and male strobilus production was positive in each of the five years studied and statistically significant with the exception of one poor flowering year. The clonal status number (Ns), a measure of genetic diversity, was calculated based on the observed clonal fertility variation, varying from 27.6 (N = 40) in the poorest flowering year (2002) to 35.8 in the best year (2005). On average (pooled), the relative status number was 95% of the census number (N). Variation of female fertility was higher than that of male fertility for the five consecutive years, and the status numbers of female and male parents reflected this variation. The pooled Ns estimation from all five years was higher than any single year, implying that genetic diversity would increase when seeds collected from different years are pooled. Sexual asymmetry calculations showed that clonal contributions would be balanced between genders