Pines are believed to be among the oldest living trees on Earth. Pines produce cones and have needlelike leaves. The oldest known bristlecone pine is 4,900 years old, but they can live for as long as 6,000 years.

Where pines grow

Pines are most commonly found in mountainous regions. They are primarily native to regions with moderate climates, such as in the cool regions of the Northern Hemisphere. About 35 of the 90 species are native to North America.

Physical characteristics

Young pines are usually pyramid-shaped. Groups of horizontal branches encircle the plant stem. Older trees may have round, flat, or spreading tops. The bark is usually thick, scaly, and wrinkled. The trees range in height from only a few feet to well over 200 feet (61 meters) tall. It takes a year or two for pine trees to develop adult needles. The needles remain on the tree for 2 to 17 years.

Pine trees can tolerate drought but require full sunlight and clean air for good growth and reproduction.

Types of pines

Pines can be divided into two groups, soft pines and hard pines. This grouping is based on the way their needles grow, the structure of their cones, and the type of wood.

Soft pines have covered needles that usually grow in bunches of five. The cones do not have prickles, or spikes. The wood is relatively soft and contains small quantities of a liquid substance called resin. Some examples of soft pines include the eastern and western white pines as well as the limber, bristlecone, piñon, and sugar pines. The sugar pine produces the largest cones of any North American pine. The cones can reach lengths of 20 inches (51 centimeters).

Hard pines have covered needles that grow in groups of two or three. The dark-colored wood is relatively hard, with large amounts of resin. The red, or Norway, pine is a hard pine of pale reddish wood. Other hard pines include the Scotch pine, the lodgepole, longleaf, shortleaf, loblolly, and slash pines.

Life cycle

Pines produce separate male and female cones on the same tree. Usually the male cones appear in clusters on the lower branches of the tree and the female cones on the upper branches. At a length of less than 1 inch (2.5 centimeters), male cones are smaller than female cones.

Male cones are covered with many fertile scales. Each scale contains two pollen sacs. The female cones are generally referred to as pinecones. They consist of winding scales that overlap. Each scale contains two ovules that develop into seeds. These scales are covered by bracts.

In spring or early summer, pollination occurs. Pollination is the process by which the female part of a plant is fertilized. The male pollen sacs release their pollen to the wind. The wind carries the pollen to other trees. The scales on the female cones open to receive the pollen and then close.

Actual fertilization does not occur until the spring of the following year. Even after fertilization, the small, green female cones take almost two to three years to develop. Eventually they grow large and woody and become brown in color. In some species the cones open at maturity and release their seeds. In others the cones remain closed for several years. When they open, it is mostly due to rotting, food-seeking animals, or fire.

Diseases

Pines are sensitive to several fungal diseases, as well as to attack by insects such as sawflies, weevils, bark beetles, and tip moths. Pine forests burn easily because of their high resin content. They often suffer severe damage by fire.

Uses

Pine trees are a major source of timber. Their wood is used in construction and paper-product industries. Paper is made from the pulpwood of many pines. The resin of pine trees is also valuable for use in such products as turpentine, rosin, oils, and wood tars.

The resin present in the bark of pine trees is a natural antiseptic used by the tree against infection. The resin also provides many products such as paints and varnishes. Pine oil is extracted and used as medicine. Edible pine seeds are sold commercially as pine nuts, piñons, or pignons. Many species of pines are cultivated for decorative purposes. They are also used for reforestation and windbreaks. In a windbreak, a growth of trees or shrubs serves to break the force of the wind.