The pine tree is one of the most recognizable trees in the world. In North America, there are 36 native species of pine tree. These species are divided between West Coast pines, East Coast pines and Southern pines. Pines are abundant in areas with sandy soils, such as the mountainous West and the South. Classified as conifers, pine trees bear cones instead of fruit.
Pine trees have needles instead of leaves. Needles are attached to the branch in clusters, and pines are classified by how many needles in each cluster. The single-leaf pinyon has one needle. Two-needle pines include jack, Virginia, spruce, sand and red. Three-needle pines include pinyon, Monterey, loblolly and longleaf. The parry pinyon has four needles, according to the "Field Guide to Trees of North America" by the National Wildlife Association. Five-needle pines include Western pines such as the Colorado bristlecone, whitebark, Western white and sugar pine.
Pine pollen cones are small, cover the new shoots and release pollen. Cones that cover seeds are larger and have wooden scales that often are pointed on the edge. The majority of pine cones have short stalks that attach them to the branches. The Torry pine is the exception, having a long-stalked cone. Pine cones mature in their second year, opening up and dropping their seeds. In certain species, such as the shortleaf pine, sand pine, coulter pine and gray pine, old cones remain on the tree for a number of years.
Certain pine trees such as pitch, pond, lodgepole, knobcone, bishop and Monterey have fire cones. These cones are attached to the tree and encased in wax. In the event of a fire, the cones drop to the ground and the heat from the fire melts the wax. The cone slowly opens its scales and drops seeds over the course of several weeks, effectively reseeding the burned area. Pine trees with fire cones also have regular cones.
Pine seeds that are edible are called pine nuts. These nuts are a food source for birds and small mammals who store the seeds for later use. These stores are raided by other animals, including bears, according to the U.S. Department of Agriculture Forest Service. Smaller pine nuts have a wing that makes them easily dispersed by wind. Nuts from the Mexican pinyon pine are harvested for human consumption. These nuts are large and oily.
Pine trees, except for the spruce pine, grow fast in full sun. The growth rate of trees in shaded forests is slower. After fires, pine tree numbers increase due to the absence of competition for sunlight. Pines such as ponderosa, sugar and Jeffrey withstand forest fires. Certain species have adapted to difficult conditions, such as the scotch pine, which tolerates drought and salt; pond pine, which grows in wetland-like swamps; and Monterey pine, which grows in the foggy, seaside climate of the California coast.