Pine cones are the reproductive organs of pine trees. The cones are either male or female. Most pine tree species have both sexes of cones on each tree. The male cones produce pollen and the female cones produce ovules. The pollen and ovules must come into contact to fertilize and produce the next generation of pine trees.
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Pine trees are conifers belonging to the category of trees called gymnosperms, a term that derives from the Greek for "naked seed." They do not produce fruits or flowers to contain their seeds. About 35 species of pine trees grow in North America, including the red pine, the shortleaf pine, the bristlecone pine and sugar pine.
Male pine cones develop from pine needles and rarely grow more than 2 inches in length. They form in clusters at the ends of the lower branches of pine trees. Male pine cones are herbaceous -- not made from wood -- and typically live for only a few months in either spring or autumn, depending on the species of tree. They produce pollen that is released into the air to find a female cone. After releasing their pollen, the male cones die and fall from the tree.
Hardier than their male counterparts -- to protect the seeds while they develop -- female pine cones develop from the end of branches or pine needles to form scales. When mature, female pine cones may grow to between 1 and 24 inches in length. Their scales contain ovules -- two per scale -- that develop into seeds when fertilized by pollen. Some pine tree species store the fertilized seeds for several years. When ready to release its seeds, in most cases the female cone opens its scales and drops to the ground, allowing the seeds to escape and, hopefully, germinate in the soil. Some seeds have small wings to enable them to disperse farther from the parent tree, while others are eaten by birds and deposited in other locations through their droppings.
Many forest animals, including squirrels, chipmunks and birds, eat the mature seeds of pine cones. Humans eat them as well. These products are usually referred to as pine nuts and typically come from the pinyon, stone and sugar varieties of pine trees. These nuts may be toasted and used as a garnish for salads or pasta, or added to pesto. They can also be eaten raw and are a good source of protein. Some people use the fallen female cones as decorations for wreaths or Christmas trees.
Some species of pine trees, known as fire climax pines, keep their fertilized seeds within especially hardened pine cones. They only open to release the seeds within the heat of a forest fire. Thus, while a forest fire may look destructive, in some cases it ensures the repopulation of the forest.