Male and female cone crop patterns and gender expression in Pinus densiflora were examined in three adjacent Korean populations over four to five years. Three parameters -- cone ratio, sexual system, and standardized phenotypic gender -- were assessed according to cone production. Both male and female cone crops and cone ratios varied by year and by site. After controlling for plant size, population differences in cone crops and cone ratios became stronger. At all three sites, the proportion of trees with differing sexual systems tended to fluctuate among years. Overall, 37% of all tagged trees changed their sexual system at least once, mostly ranging between monoecy and male. These particular trees were relatively small and exhibited slow radial growth compared with the non-sex-changing trees, suggesting a trade-off between vegetative and reproductive growth. Despite annual variations in their standardized phenotypic genders, the rankings of trees remained concordant between successive years at all sites. These results indicate that, in P. densiflora, male and female cone crops and, consequently, gender expression, may be affected by diverse factors that include plant size, trade-offs between vegetative and reproductive growth, and genetic components.