Laboratory of Biochemical Ecology, University of Kentucky, Lexington, KY 40506, garose@pop.uky.edu 

Members of the Coniferales or conifers are the economically most important and widespread group of gymnosperms. They are prevalent at high altitutes and in the cold regions of the temperate zone. Almost all are arborescent and their wood is used widely for timber and as a source for pulp (fiber) for paper-making and related industrial uses.

These plants are typically pyrimidal and the massive main axis (trunk or bole) is the primary source for merchantible timber. They are able to gain impressive heights, often exceeding 300 feet in the giant sequoia, and redwood forests of California and in sitka spruce and douglas-fir that reside in the temperate rain forest of the Olympic peninsula.

The growth in girth that can produce individuals with a diameter at breast height of more than 30 feet . Conifers are perennial since their vegetative tissues are persistent and last many years. The western hemlock of the Olympic peninsula live to 500 years, the sitka spruce to 600, but the other two dominant trees of this temperate rain forest: western red cedar and douglas-fir can survive a century. Far longer-lived are the redwoods and giant sequoia, but the longevity record is held by bristlecone pine which can reach 5,000 years in age.

Conifer leaf morphology is varied but nearly always small and simple in shape that ranges from needlelike structures (several cm in length) to closely appressed scales that extend only a few mm. The leaves are borne on short shoots that persists for several seasons. Only in a few genera such as larch, Larix is the foliage truly deciduous.

Leaves:

Water loss is retarded by an external cuticle and a hypodermis-heavily lignified cells. Resin canals are frequent and in some species such as the cedars, Thuja, a fragrant oil is contained within a prominent gland on the back of the leaf.

Remarkably resistant to frost damage and able to photosynthesize at low temperature. Pyramidal form and the ddiagravitropic branches of many conifers are efficient in capturing the low-angle light that is characteristic of high latitudes.

Reproductive organs are borne in cones. Most conifers are monoecious, the male and female cones are produced in distinct parts of the plant. In pines, Pinus, the female cones are found near the apex of the tree and near the main lateral buds. The male cones are distributed on the lower branches, usually in groups. A few conifers such as the yews, Taxus, and the cedars, Juniperus are dioecious.

Stems:

PINE

The pines (Pinus) are the most abundant genus of conifers in North America. These plants are characterized by straight, unbranched, cylindrical trunks and foliage that is needle-like and rounded. All pines bear 1-5 needles that are arranged in groups and bundled together to form a fascicle. The usually pendent cone is made of hard, woody material, often armored with a sharp prickle. Two seeds, often papery winged, are borne on each scale.

SPRUCE

The spruces (Picea) typically possess a sharp-pointed, pyramidal crown and branches that descend in a pattern of whorls. The needles are 4-sided or flattened, spirally arranged around the twig, and are attached to the twig without a stalk. They exhibit stomata on their upper-side, and are supported by a wooden peg or sterigmata. The cones are soft, almost papery, and concentrated at the apex of the tree.

CEDAR

The cedars (Cupressus) produce a scale-like leaf that can form flat, horizontally feathery sprays. The fruit is a spherical structure made of interlocking scales that are shield-shaped and attached to the stalk of the cone at its lower surface, raised structures can project from these scales.

JUNIPER

The junipers (Juniperus) are generally small and highly aromatic trees that have needle- or awl-like juvenile foliage, but can be scale-like at maturity. The fruit is an indehiscent cone that is superficiallly berry-like in appearance, succulent, and often highly aromatic.

HEMLOCK

The hemlocks (Tsuga) are tall, broadly pyramidal, often with drooping pendent branch es. The foliage is spirally arranged, linear, and solitary. Needles are flattened, and possess a small, terminal stalk that attaches to the twig. Dual bands of conspicuously-colored (whitish) stomata occur on the underside. The immature cones are small, pendent, closed, soft and deeply green but at maturity then open, and become brown and papery.

DOUGLAS-FIR

Douglas fir (Pseudotsuga menziesii) is a conifer distinct enough to merit its own genus. The foliage is linear, solitary, flattened, and spirally arranged. Distinctive for its pendent, papery cone that bears three-lobed bracts that protude from the cone. The winter buds are long (0.25"), conical and sharply pointed with a lustrous brown coloration.

FIR

The true firs (Abies) produce spirally-arranged, linear, sessile foliage that is typically flat and blunt. The needles bear stomata on the underside, but they are not as conspicuous as in Tsuga. The cones are soft like Picea but always erect.