Pine cones form by cross-pollination between two trees. Seed cones and pollen cones are the two types of cones that grown on the same pine tree.
A pine cone is a cluster of modified scales of wood that are tightly packed together. This structure helps to protect the inside of the cone where conifer seeds are developing. Since pine cones are formed by cross-pollination, it is important that conifer seeds are dispersed, which can occur by the wind or animals. Seeds carried by the wind are relatively small and have a wing, while seeds carried by animals are large and do not have a wing.
The cone cycle does not occur yearly. When the cone cycle does occur, it begins in the spring after new shoots have elongated. Seed cones form at the ends of the elongated shoots while pollen cones gather in clusters underneath the terminal bud at the base of the shoots, and the formation usually occurs on opposite ends of the tree. Pollen cones are located on the lower branches of the tree while seed cones are located on the upper branches of the tree. Pollen cones never travel up to the seed cones on the same tree, so cross-pollination between trees must occur for the two seed types to interact and germinate.