Holly trees are dioecious, meaning they have male and female flowers. Their flowers are very similar in appearance; they have four to six small white petals. However, male flowers appear in clusters, where as female flowers appear singlularly along the branches. In the tree's southern range, flowering starts in April. In the northern range, flowering starts closer to June. Male trees pollinate female trees. Bees, moths, yellow-jackets, and other insects perform pollination.