Coniferales is the largest group among the gymnosperms represented by about 500 living species of cone-bearing plants. Some conifers are not only among largest plants on earth but also as old as 3000 years or more. They are worldwide in distribution forming the extensive forests in northern and southern hemisphere.

Conifers are generally woody, either branched trees or distinct shrubs. Habit of plants is excurrent, i.e. Lower branches of trees are longer and more horizontal than the upper ones giving conical appearances to the plant. The plants are evergreen, i.e. foliage leaves function for more than one year and profusely branched. Branching is monopodial and usually the branches are of two types -Branches of unlimited growth and branches of limited growth. Usually the leaves are of two types – the foliage leaves and scale leaves. The root system is extensively branched tap-root system. The roots are usually mycorrhizal. The primary vascular cylinder of stem is eustelic consisting of conjoint, collateral, open and endarch vascular bundles. Resin ducts are present. Secondary xylem is homogeneous and pycnoxylic.

Conifers are usually monoceious, i.e. male and female cones are borne on the same plant. Cones are compact and woody but not produced on the tips of the main branches. They have an advantage over angiosperms because they are evergreen, i.e. their leaves are not shed and trees do not become bare in winters, the angiospermsous trees, on the other hand, are deciduous and shed their leaves and become bare in winters.

Conifers have a number of xerophytic characters such as needle-like, scale-like, or small and leathery leaves, thick cuticle, sclerenchymatous hypodermis and sunken stomata to reduce transpiration. They are, thus, well adapted to tide over the winter period when the soil becomes frozen and availability of water is very little. The roots of conifers are mycorrhizal or fungal symbionts which help them to absorb water and minerals from the soil rich in organic debris.

Conifers posses special ducts, filled with aromatics, antiseptic, sticky semi fluid substances called resin which exudes and seals the damaged or injured areas of plants. Turpentine is extracted from resin which is highly inflammable. Due to presence of resin it is very difficult to extinguish fire in pine forests. The resin also protects the trees from attack of microbes and insects.

Evergreen coniferous trees continue to photosynthesize throughout the year when the other plants cannot do so because of the absence of leaves from autumn to spring and they are in a state of hibernation during the periods.