The strain ‘GW’ obtained by selfing in cucumber variety ‘Hi-green’, represented trimonoecious sex expression with hermaphrodite flowers similar to female flowers in shape. The hermaphrodite flowers usually turned into female flowers with rudimentary stamens in later stages of development, i.e. at upper stem nodes, and under low temperature conditions. From a genetic analysis, it was determined that the trimonoecious sex expression was controlled by a recessive gene tentatively designated h’.