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Why do pine trees have cones?

Updated July 19, 2017

Pine cones are the reproductive organs of pine trees. Like many other plants, pine trees reproduce sexually. They need both male and female cells in order to create the next generation of pine trees. Each pine cone is either male or female. Male pine cones produce pollen and female pine cones produce ovules. The dry, prickly pine cone you find on the ground near a pine tree is probably a female cone that has already released its seeds.

Background

Pine trees are evergreen conifers. They belong to the category of gymnosperms, which is Greek for "naked seed." Gymnosperms do not produce flowers or fruits. Their seeds develop without the protection of a hard seed coat, berry or fruit. A timeline from the San Diego Natural History Museum on evolutionary history indicates that gymnosperms appeared about 360 million years ago, about 200 million years before flowering plants.

Male Cones

The male pine cones are generally herbaceous, or nonwoody. Their function is to produce large quantities of pollen. Male cones generally grow in clusters at the tips of lower pine branches. According to Maricopa College, it can take several years for male cones to mature and produce pollen. When the pollen is mature, it is released into the air and carried by the wind to land on and fertilise the ovules in female cones.

Female Cones

Female cones develop from the ends of branches and pine needles that change, grow, specialise and harden to form scales. There are two types of scales. The bract scales develop first. Their function is to provide a platform for the seed scales, which each produce two ovules that grow into two seeds after fertilisation by pollen. The process of producing mature seeds takes two years. During the first year, the bracts open to accept pollen, and then close again to hold the pollen inside with the ovule. The pollen does not germinate and fertilise the ovule until the next year. It can take another year for the seed to mature. Then, the bracts open again and release the seeds.

Edible Pine Nuts

The mature seeds of the pine tree are often eaten by forest animals such as squirrels and chipmunks. People eat many kinds of pine seeds, including those of the piƱon pine, stone pine and sugar pine trees. Pine nuts are high in protein, and many people find them delicious. They may be added to basil pesto or as a garnish on salads. The stone pine has been cultivated for that purpose in Italy for more than 6,000 years. If you have ever eaten pignolia nuts, you have eaten the seeds of the stone pine tree.

Fun Facts

The San Bernardino Pine Cone Festival coordinators list many fun facts about pine cones. For instance, the heaviest pine cone in the world is the coulter pine cone, which can weigh up to 4.54kg. The knobcob pine is extremely hard--it relies on the heat of a wildfire to force it to open and release its seeds. The longest pine cone comes from the sugar pine, whose cones can be 2 feet long, and the Jeffrey pine is called the "gentle Jeffrey" because the sharp points on the scales are turned inward and thus it is not prickly to handle.

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About the Author

Rose Guastella is a professional artist and teacher from Kitsap County, Wash. She has been writing educational materials for schools since before 1990. Guastella holds a Master of Arts in liberal studies from the State University of New York at Stony Brook. She has contributed several articles about education and plant biology to various websites.