[en] Idesia polycarpa Maxim. is a promising plant for biodiesel in China. We have reported the flowering phenology, breeding system and parental effect on fruit characters of this species distributed in Qinling-Bashan Mountain (Shaanxi Province) nature reserve. As a dioecious plant, the male and female flowered almost synchronously. The anthesis was from around 10th of May and proceeded until the end of May or the beginning of June at population level. To determine the breeding system of I. polycarpa, three pollination treatments were carried out on every three female plants: natural pollination (NP), apomixy (AP) and cross pollination (CP). Reproductive success of apoximy treatment indicated that, as a dioecious plant, I. polycarpa could also reproduce by apomixis. However, the mean fruit set under apomixy treatment was markerly lower (3.6–13.33%) than that of two pollination treatments (>65.69%). Fruit quality (fruit length, fruit width, 100 fruit weight, seed production and seed germination) of the cross pollination treatment was greater than the other two treatments, suggested that pollen competition in cross pollination treatment was the most intense in three treatments. To study parental effect on fruit characters, cross pollination was carried out with three female plants and three male plants. The result showed that maternal parents (P<0.001) and parental interaction significantly affected all the fruit characters (including 100 fruit weight, pulp/fruit ratio, oil content and seed germination) while paternal parents showed significant effects on 100 fruit weight, pulp/fruit ratio and seed germination. Fruit set was only significantly affected by maternal parents (P=0.001). Our findings will facilitate future breeding programs of I. polycarpa in parental selection. (author)