A pine cone is an organ of the pine tree containing its reproductive structures. Pine trees are only one of the conifer, or "cone-bearing," plants; others include cedars, firs, cypresses, and redwoods. Pine cones, like the reproductive organs of other conifers, come in male and female varieties. In most species of pine, male and female cones grow on the same tree. The trees of some species have cones predominantly of only one sex, with a few of the opposite sex.
Pinus is a genus of trees with about 115 species. While all produce cones, their size and appearance differ slightly, and male and female cones also look different from each other. The image that most people associate with the pine cone, a woody, scaled structure, is actually the female structure. Male cones are smaller, more herbaceous, and shorter lived.
The male cone is usually no more than 2 inches (5 cm) long and lives for only a few months in the spring or the autumn, depending on the species of pine. It is covered with microsporangia, or pollen sacs. After it releases its pollen, it falls off the tree.
After the male cones release their pollen, it travels by wind to the female pine cones. After pollination, the female cone takes one and a half to three years to mature. Fertilization, the fusion of the sperm in the pollen with the ovary in the female seed, takes place a year after pollination. There are two seeds on each fertile scale of the female cone; the scales at either end of the cone are too small to support seeds.
Female cones are much hardier than their male counterparts, as they are designed to last until the seeds are dispersed. In some species, fertilized seeds are stored for years. Mature female cones are typically 1 to 24 inches (3 to 60 cm) in length.
In most pine species, mature female cones open to release their seeds when they reach maturity. Usually, the seeds have wings and are dispersed by the air. In some species of pine, however, the seeds have only a vestigial wing and are dispersed by birds. Some pines require the birds to break the cones open in order for the seeds to be released.
Some species, known as fire climax pines, store fertilized seeds inside pine cones that can only be opened by the heat of a forest fire. When a fire destroys living trees, fire climax pines release their seeds to repopulate the forest.