Conifers () are a group of vascular plants and a subset of gymnosperms. They are primarily perennial, woody trees and shrubs, mostly evergreen with a regular branching pattern, reproducing with male and female cones, usually on the same tree. They are wind-pollinated and the seeds are usually dispersed by the wind. Taxonomically, they make up the division Pinophyta, also known as Coniferae. All extant conifers, except for the gnetophytes, are perennial woody plants with secondary growth. There are over 600 living species. Conifers first appear in the fossil record over 300 million years ago in the Carboniferous. They became dominant land plants in the Mesozoic, until flowering plants took over many ecosystems in the Cretaceous. Many conifers today are relict species, surviving in a small part of their former ranges. Such relicts include Wollemia, known only from a small area of Australia, and Metasequoia glyptostroboides, known from Cretaceous fossils and surviving in a small area of China. Although the total number of species is relatively small, conifers are ecologically important. They are the dominant plants over the taiga of the Northern Hemisphere. Boreal conifers have multiple adaptations to survive winters, including a conical shape to shed snow, strong tracheid vessels to tolerate ice pressure, and a waxy covering on the needle leaves to minimize water loss. Several fungi form ectomycorrhizal associations with conifers, while other fungi cause diseases such as needle cast, which is especially harmful to young trees. Conifers are affected by pest insects such as wood-boring longhorn beetles and by bark beetles, which make galleries just under the bark. As of 2025, 94 conifer species are listed as endangered and 30 as critically endangered. Conifers are of great economic value for timber and paper production.
Description All extant conifers are woody plants; most are trees that bear narrow leaves, often acicular (needle-shaped). An individual conifer produces separate male and female reproductive structures – two distinct types of cone. Pollination is always by wind; the seeds are mostly winged samaras. The trees have a regular branching pattern. Many conifers have distinctly scented resin. The world's tallest and oldest living trees are conifers. The tallest is a coast redwood (Sequoia sempervirens), with a height of 116.07 metres (380.8 ft). Among the smallest conifers is the pygmy pine (Lepidothamnus laxifolius) of New Zealand, which is seldom taller than 30 cm when mature. The oldest non-clonal living tree is a Great Basin bristlecone pine (Pinus longaeva), 4,700 years old. Boreal conifers have multiple adaptations to survive winters, including the tree's conical shape to shed snow, strong tracheid vessels to tolerate ice pressure, and a waxy covering on the needle leaves to minimize water loss.
Foliage Most conifers are evergreens, retaining functional foliage throughout the year. In many species such as pines, firs, and cedars, the leaves are long, thin and needle-like. Others like cypresses have flat, triangular scale-like leaves. In the majority of conifers, the leaves are arranged spirally, the exceptions being most of Cupressaceae and one genus in Podocarpaceae, where they are arranged in decussate (crossing) opposite pairs or whorls of 3 or 4. In many species with spirally arranged leaves, such as Abies grandis, the leaf bases are twisted to present the leaves in a flat plane for maximum light absorption. Leaf size varies from 2 mm in many scale-leaved species, up to 600 mm (24 in) long in the needles of some pines (e.g. longleaf pine, ponderosa pine). The stomata are in lines or patches on the leaves and can be closed when it is very dry or cold. The leaves are often dark green in color, which may help absorb a maximum of energy from weak sunshine at high latitudes or under forest canopy shade. Conifers from lower latitudes with high sunlight levels (e.g. Turkish pine Pinus brutia) often have yellower-green leaves, while others (e.g. blue spruce, Picea pungens) may develop blue or silvery leaves reflect ultraviolet light. In the great majority of genera the leaves remain on the plant for several (2–40) years before falling, but five genera (Larix, Pseudolarix, Glyptostrobus, Metasequoia and Taxodium) are deciduous, shedding their leaves in autumn. The seedlings of some conifers, including pines, have a distinct juvenile foliage period where the leaves are different from the typical adult leaves.
Wood
The microscopic structure of conifer wood (xylem) is homogeneous, and consists of two types of cells: parenchyma, which have an oval or polyhedral shape, and strongly elongated tracheids. Tracheids make up more than 90% of timber volume. Conifers produce growth rings, normally gently curved in their outline, but in Taxus, Juniperus, and Cupressaceae are undulating. The tracheids of earlywood formed at the beginning of a growing season have large radial sizes and smaller, thinner cell walls. Then, the first tracheids of the transition zone are formed, where the radial size of cells and the thickness of their cell walls changes considerably. Finally, latewood tracheids are formed, with small radial sizes and greater cell wall thickness. This is the basic pattern of the internal cell structure of conifer tree rings. Frost rings have been observed in Cupressaceae. Conifer wood contains medullary rays, primarily composed of parenchymal cells, and involved in radial gas exchange, as a conduit for storage of water and nutrients, and as a pathway for diffusing heartwood substances. The latewood in particular also contains resin canals. These are surrounded by specialised epithelial cells that secrete resin into the canal. Radial and axial resin canals are interconnected throughout the wood. Conifers secrete oleoresin, a composite of turpentine and rosin. When an insect or a fungus attacks, oleoresin flows into the wound. It traps invading insects and blocks fungi. The rosin hardens and seals the wound, protecting against damage. During wet weather, the Gitxsan harvest conifer rosin for use as fire starters.
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