Pine

The bark of most pines is thick and scaly, but some species have thin, flaky bark.[11] 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.

Pines have four types of leaf:

• Seed leaves (cotyledons) on seedlings are borne in a whorl of 4–24.
• Juvenile leaves, which follow immediately on seedlings and young plants, are 2–6 cm long, single, green or often blue-green, and arranged spirally on the shoot. These are produced for six months to five years, rarely longer.
• Scale leaves, similar to bud scales, are small, brown and not photosynthetic, and arranged spirally like the juvenile leaves.
• Needles, the adult leaves, are green (photosynthetic) and bundled in clusters called fascicles. The needles can number from one to seven per fascicle, but generally number from two to five. Each fascicle is produced from a small bud on a dwarf shoot in the axil of a scale leaf. These bud scales often remain on the fascicle as a basal sheath. The needles persist for 1.5–40 years, depending on species. If a shoot's growing tip is damaged (e.g. eaten by an animal), the needle fascicles just below the damage will generate a stem-producing bud, which can then replace the lost growth tip.

Pinus radiata female (ovulate) cone

P. radiata male (pollen) cone

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). Female cones are woody and sometimes armed to protect developing seeds from foragers. At maturity, the cones usually open to release the seeds. In some of the bird-dispersed species, for example whitebark pine,[12]), the seeds are only released by the bird breaking the cones open. In others, the seeds are stored in closed cones for many years until an environmental cue triggers the cones to open, releasing the seeds. This is called serotiny. The most common form of serotiny is pyriscence, in which a resin binds the cones shut until melted by a forest fire, for example in Pinus rigida.

Pine forest in Vagamon, southern Western Ghats, Kerala (India)

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.[20] Nutrients from pollen aid detritivores in development, growth, and maturation, and may enable fungi to decompose nutritionally scarce litter.[20] Pine pollen is also involved in moving plant matter between terrestrial and aquatic ecosystems.[20]

Logging Pinus ponderosa, Arizona, USA

Pines are among the most commercially important tree species valued for their timber and wood pulp throughout the world.[21][22] 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.[23]

"Pine Clouds", 1903 painting on fan by Wu Ku-hsiang

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.[24] 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.[25] 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.[26]

Pine beauty moth (Panolis flammea) on pine needles

Pine needles serve as food for various Lepidoptera. Several species of pine are attacked by nematodes, causing pine wilt disease, which can kill some quickly. Some of these Lepidoptera species, many of them moths, specialize in feeding on only one or sometimes several species of pine. Beside that many species of birds and mammals shelter in pine habitat or feed on pine nuts.

When grown for sawing timber, pine plantations can be harvested after 25 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 or are left in the forest, while most older ones are good enough for saw timber.[27]

A 30-year-old commercial pine tree grown in good conditions in Arkansas 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. This however depends on the region, species and silvicultural techniques. In New Zealand plantations maximum value is reached at around 28 years with height being as high as 30 m (98 ft) and diameter 0.5 m (1.6 ft) and maximum wood production around 35 years (again depending on factors such as site, stocking and genetics). Trees are normally planted 3–4 m apart, or about 1000 per hectare (100,000 per km²). [28][29][30][31]

Edible seeds of the Korean pine (Pinus koraiensis)

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) beneath the woody outer bark is edible and very high in vitamins A and C.[32] 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.[33]

Pine needles from Pinus densiflora were found to contain 30.54 mg/g of proanthocyanidins when extracted with hot water.[34] 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.[35]

Writers of various nationalities and ethnicities have written of pines. Among them, John Muir,[36] Dora Sigerson Shorter,[37] Eugene Field,[38] the Chinese,[39] Theodore Winthrop,[40] and Rev. George Allan D.D.[41]

Under the Pines, Evening, Claude Monet (1888) (Philadelphia Museum of Art)

By Camille Pissarro.

Pines are often featured in art, whether painting and fine art,[42] drawing,[43] 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:[44]

"And that they should publish and proclaim in all their cities, and in Jerusalem, saying, Go forth unto the mount, and fetch olive branches, and pine branches [emphasis added], and myrtle branches, and palm branches, and branches of thick trees, to make booths, as it is written."

Pines are also mentioned in Isaiah 60:

"13: The glory of Lebanon shall come unto thee, the fir tree, the pine tree, and the box together, to beautify the place of my sanctuary; and I will make the place of my feet glorious."

Many Chinese ink sticks are made out of pine: the wood being burnt and the soot collected as an ingredient to provide the coloring

The pine is a motif in Chinese art and literature, which sometimes combines painting and poetry in the same work. Some of the main symbolic attributes of pines in Chinese art and literature are longevity and steadfastness: the pine retains its green needles through all the seasons. Sometimes the pine and cypress are paired. At other times the pine, plum, and bamboo are considered as the "Three Friends of Winter".[45] Many Chinese art works and/or literature (some involving pines) have been done using paper, brush, and Chinese ink: interestingly enough, one of the main ingredients for Chinese ink has been pine soot.