A pine is any conifer in the genus Pinus (/ˈpiːnuːs/^[1] subfamily Pinoideae d by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts 126 species names of pines as current, together with 35 unresolved species and many more synonyms.^[2]

The modern English name "pine" derives from Latin pinus, which some have traced to the Indo-European base *pīt- ‘resin’ (source of English pituitary).^[3] Before the 19th century, pines were often referred to as firs (from Old Norse fura, by way of Middle English firre). In some European languages, Germanic cognates of the Old Norse name are still in use for pines—in Danish fyr, in Norwegian fura/fure/furu, Swedish fura/furu, Dutch vuren, and German Föhre—but in modern English, fir is now restricted to fir (Abies) and Douglas fir (Pseudotsuga).

Pine trees are evergreen, coniferous resinous trees (or, rarely, shrubs) growing 3–80 m (10–260 ft) tall, with the majority of species reaching 15–45 m (50–150 ft) tall. The smallest are Siberian dwarf pine and Potosi pinyon, and the tallest is an 81.79 m (268.35 ft) tall ponderosa pine located in southern Oregon's Rogue River-Siskiyou National Forest.^[4]

Pines are long lived and typically reach ages of 100–1,000 years, some even more.

The longest-lived is the Great Basin bristlecone pine, Pinus longaeva. One individual of this species, dubbed "Methuselah", is one of the world's oldest living organisms at around 4,600 years old. This tree can be found in the White Mountains of California.^[5] An older tree, now cut down, was dated at 4,900 years old. It was discovered in a grove beneath Wheeler Peak and it is now known as "Prometheus" after the Greek immortal.

The bark of most pines is thick and scaly, but some species have thin, flaky bark. The branches are produced in regular "pseudo whorls", actually a very tight spiral but appearing like a ring of branches arising from the same point. Many pines are uninodal, producing just one such whorl of branches each year, from buds at the tip of the year's new shoot, but others are multinodal, producing two or more whorls of branches per year.

The spiral growth of branches, needles, and cone scales may be arranged in Fibonacci number ratios. The new spring shoots are sometimes called "candles"; they are covered in brown or whitish bud scales and point upward at first, then later turn green and spread outward. These "candles" offer foresters a means to evaluate fertility of the soil and vigour of the trees.

Pines have four types of leaf:

Pines are mostly monoecious, having the male and female cones on the same tree, though a few species are sub-dioecious, with individuals predominantly, but not wholly, single-sex. The male cones are small, typically 1–5 cm long, and only present for a short period (usually in spring, though autumn in a few pines), falling as soon as they have shed their pollen. The female cones take 1.5–3 years (depending on species) to mature after pollination, with actual fertilization delayed one year. At maturity the female cones are 3–60 cm long. Each cone has numerous spirally arranged scales, with two seeds on each fertile scale; the scales at the base and tip of the cone are small and sterile, without seeds.

The seeds are mostly small and winged, and are anemophilous (wind-dispersed), but some are larger and have only a vestigial wing, and are bird-dispersed (see below). At maturity, the cones usually open to release the seeds, but in some of the bird-dispersed species (e.g. whitebark pine), the seeds are only released by the bird breaking the cones open. In others, the seeds are stored in closed ("serotinous") cones for many years until an environmental cue triggers the cones to open, releasing the seeds. The most common form of serotiny is pyriscence, in which a resin binds the cones shut until melted by a forest fire.

Conifers evolved about 300 million years ago, and pines perhaps around 153 million years ago.

The genus Pinus is thought to have diverged from other pines approximately 95 million years ago.

Pines are gymnosperms. The genus is divided into two subgenera, which can be distinguished by cone, seed, and leaf characters:

Pines are native to the Northern Hemisphere, and in a few parts of the tropics in the Southern Hemisphere. Most regions of the Northern Hemisphere (see List of pines by region) host some native species of pines. One species (Sumatran pine) crosses the equator in Sumatra to 2°S. In North America, various species occur in regions at latitudes from as far north as 66°N to as far south as 12°N.

Pines may be found in a very large variety of environments, ranging from semi-arid desert to rainforests, from sea level up to 5,200 metres (17,100 ft), from the coldest to the hottest environments on Earth.

They often occur in mountainous areas with favorable soils and at least some water.

Various species have been introduced to temperate and subtropical regions of both hemispheres, where they are grown as timber or cultivated as ornamental plants in parks and gardens. A number of such introduced species have become naturalized, and some species are considered invasive in some areas^[7] and threaten native ecosystems.

Pines grow well in acid soils, some also on calcareous soils; most require good soil drainage, preferring sandy soils, but a few (e.g. lodgepole pine) can tolerate poorly drained wet soils. A few are able to sprout after forest fires (e.g. Canary Island pine). Some species of pines (e.g. bishop pine) need fire to regenerate, and their populations slowly decline under fire suppression regimens.

Several species are adapted to extreme conditions imposed by elevation and latitude (e.g. Siberian dwarf pine, mountain pine, whitebark pine, and the bristlecone pines). The pinyon pines and a number of others, notably Turkish pine and gray pine, are particularly well adapted to growth in hot, dry semidesert climates.

The seeds are commonly eaten by birds, such as grouse, crossbills, jays, nuthatches, siskins, and woodpeckers, and by squirrels. Some birds, notably the spotted nutcracker, Clark's nutcracker, and pinyon jay, are of importance in distributing pine seeds to new areas. Pine needles are sometimes eaten by some Lepidoptera (butterfly and moth) species (see list of Lepidoptera that feed on pines), the Symphytan species pine sawfly, and goats.

Pine pollen may play an important role in the functioning of detrital food webs.^[8] Nutrients from pollen aid detritivores in development, growth, and maturation, and may enable fungi to decompose nutritionally scarce litter.^[8] Pine pollen is also involved in moving plant matter between terrestrial and aquatic ecosystems.^[8]

Pines are among the most commercially important tree species valued for their timber and wood pulp throughout the world.^[9][10] In temperate and tropical regions, they are fast-growing softwoods that grow in relatively dense stands, their acidic decaying needles inhibiting the sprouting of competing hardwoods. Commercial pines are grown in plantations for timber that is denser and therefore more durable than spruce (Picea). Pine wood is widely used in high-value carpentry items such as furniture, window frames, panelling, floors, and roofing, and the resin of some species is an important source of turpentine.

Because pines have no insect- or decay-resistant qualities after logging, untreated they are generally recommended for construction purposes as indoor use only (indoor drywall framing, for example). For outside use, pine needs to be treated with copper azole, chromated copper arsenate or other suitable chemical preservative.^[11]

Many pine species make attractive ornamental plantings for parks and larger gardens with a variety of dwarf cultivars being suitable for smaller spaces. Pines are also commercially grown and harvested for Christmas trees. Pine cones, the largest and most durable of all conifer cones, are craft favorites. Pine boughs, appreciated especially in wintertime for their pleasant smell and greenery, are popularly cut for decorations.^[12] Pine needles are also used for making decorative articles such as baskets, trays, pots, etc, and during the U.S. Civil War, the needles of the longleaf pine "Georgia pine" were widely employed in this.^[13] This originally Native American skill is now being replicated across the world. Pine needle handicrafts are made in the US, Canada, Mexico, Nicaragua, and India. Pine needles are also versatile and have been used by Latvian designer Tamara Orjola to create different biodegradable products including paper, furniture, textiles and dye.^[14]

Pine needles serve as food for various Lepidoptera. See List of Lepidoptera that feed on pines. Several species are attacked by nematodes, causing pine wilt disease, which can kill some quickly.

When grown for sawing timber, pine plantations can be harvested after 30 years, with some stands being allowed to grow up to 50 (as the wood value increases more quickly as the trees age).

Imperfect trees (such as those with bent trunks or forks, smaller trees, or diseased trees) are removed in a "thinning" operation every 5–10 years.

Thinning allows the best trees to grow much faster, because it prevents weaker trees from competing for sunlight, water, and nutrients.

Young trees removed during thinning are used for pulpwood, while most older ones are good enough for saw timber.

The final wood quality can be improved by pruning small branches at ages 5, 7, and 9.

Pruning usually goes up to a height of 6 metres (20 ft).

This results in smooth timber with no knots, which is considerably more valuable.

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A 30-year-old commercial pine tree grown in good conditions will be about 0.3 m (1.0 ft) in diameter and about 20 m (66 ft) high.

After 50 years, the same tree will be about 0.5 m (1.6 ft) in diameter and 25 m (82 ft) high, and its wood will be worth about seven times as much as the 30-year-old tree.

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Trees are planted 3–4 m apart, or about 1000 per hectare (100,000 per km2).

Some species have large seeds, called pine nuts, that are harvested and sold for cooking and baking. They are an essential ingredient of pesto alla genovese

The soft, moist, white inner bark (cambium) found clinging to the woody outer bark is edible and very high in vitamins A and C. It can be eaten raw in slices as a snack or dried and ground up into a powder for use as an ersatz flour or thickener in stews, soups, and other foods, such as bark bread. Adirondack Indians got their name from the Mohawk Indian word atirú:taks, meaning "tree eaters".

A tea made by steeping young, green pine needles in boiling water (known as tallstrunt in Sweden) is high in vitamins A and C. In eastern Asia, pine and other conifers are accepted among consumers as a beverage product, and used in teas, as well as wine.^[17]

Pine needles from Pinus densiflora were found to contain 30.54 mg/g of proanthocyanidins when extracted with hot water.^[18] Comparative to ethanol extraction resulting in 30.11 mg/g, simply extracting in hot water is preferable.

In traditional Chinese medicine (TCM), pine resin is used for burns, wounds and dermal complaints.^[19]

Pines have been a frequently mentioned tree throughout history, including in literature, paintings and other art, and in religious texts.

Writers of various nationalities and ethnicities have written of pines.

Among them, John Muir,^[20] Dora Sigerson Shorter,^[21] Eugene Field,^[22] the Chinese,^[23] Theodore Winthrop,^[24] and Rev. George Allan D.D.^[25]

Pines are often featured in art, whether painting and fine art,^[26] drawing,^[27] photography, or folk art.

Pine trees, as well as other conifers, are mentioned in The Bible. In Nehemiah 8:15, the King James Version renders the following translation:^[28]

Pines are also mentioned in Isaiah 41:

And in Isaiah 60: