Pines (genus Pinus) (/ˈpaɪ.nəs/[2]) are a genus of conifers in the family Pinaceae. Pinus is the sole genus in the subfamily Pinoideae. The species are trees or shrubs with their leaves in bunches, usually of 2 to 5 needles. The seeds are carried on woody cones, with two seeds to each cone scale.
Pines are widely distributed in the Northern Hemisphere; they occupy large areas of taiga (boreal forest), but are found in many habitats, including the Mediterranean Basin, and dry tropical forests in southeast Asia and Central America. Some are fire-resistant or fire-dependent.
Pine trees provide one of the most extensively used types of timber. The pine nuts are used to make dishes such as pesto, while retsina wine is flavoured with pine resin.
Pines are monoecious, having the male and female cones on the same tree.[11] 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 fertilisation 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.[10]
The seeds (pine nuts) are mostly small and winged, and are anemochorous (wind-dispersed). Some are larger, have only a vestigial wing, and are bird-dispersed. 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 resin binds the cones shut until the resin is melted by a forest fire, for example in P. radiata and P. muricata. The seeds are then released after the fire, enabling them to colonise the burnt ground with minimal competition from other plants.