General Description and Importance

Most pines have straight, tapering, undivided trunks, with rounded or pyramid-shaped crowns composed of many branches arranged in tiers, or whorls. Pines that cling to wind-swept dunes or cliffs may be stunted and twisted, with few branches. Some kinds of pines may attain a height of more than 200 feet (60 m), with trunks up to 12 feet (3.7 m) in diameter.

Each pine tree has two kinds of leaves—primary and secondary. The secondary leaves, or needles, grow in bundles called fascicles from the axil (the area between the leaf and stem) of the primary leaves. The primary leaves, which are barely visible, form a papery sheath at the base of each fascicle.

Each tree also has two kinds of reproductive organs: (1) pollen cones; and (2) seed cones. The pollen cones grow in clusters at the ends of mature branches, and may be yellow, orange, red, or purple. The immature seed cones, usually pale green, grow singly, paired, or in groups near the ends of young shoots. They mature in two or three years, growing woody and darkening to brown or purple. In some species, the seed cones open at maturity to release their seeds; in others they remain closed for several years. A seed usually has one or two wings.

The number of needles in a fascicle, the length of the needles, and the size and shape of the seed cones vary according to the species. Needles are from 1 to 18 inches (2.5 to 45 cm) long, and usually there are two to five in a fascicle. Seed cones are from 1 inch (2.5 cm) to more than 20 inches (50 cm) long, and may be slender, globe-shaped, or flattish. In some species, the scales of the seed cones have barbs on them. The term cone as used in the rest of this article refers only to the seed cone.

Pines are useful to humans not only for their timber, but for resins and oils from which turpentine, tars, insecticides, and medicines are made. Fast-growing species are used in reforestation programs. Pines are often cultivated for shade and as ornamentals. For a description of the woods of important pines and their uses, table Widely Used American Softwoods.

Traditionally, all conifers are known as softwoods, as distinguished from such broad-leaved trees as oaks and maples, which are called hardwoods. However, for commercial purposes in the United States and Canada, pines are classed as soft pines and hard pines.