Evergreen trees are trees that renew their foliage year-round, as opposed to deciduous trees which drop their leaves in the autumn and regrow them in the spring. The most common types of evergreens are coniferous trees, which commonly grow needles rather than leaves and spread their seeds through cones. However, there are also broadleaved trees that are considered evergreens, as well.
Pine Trees (Genus Pinus)
Pines are the most commonly-known evergreen trees, so much so that it is easy to mistake other conifer trees for them. They come in a variety of shapes and sizes, survive in moist to dry climates, and range in height from 15 feet to around 100 feet, depending on species. The characteristic that distinguishes pines from other evergreens is the growth of the needles; pine needles grow from the branches in clusters of two to five each, while other conifers produce their needles singly. Common types of pine trees include scotch pine, Ponderosa pine and white pine.
Fir Trees (Genus Abies)
Firs are conifers that are distinguishable by their singly-grown, two-sided (i.e., flat) needles, which are usually soft to the touch. Unlike pines, which may grow in wet to dry soil, firs tend to prefer moist soil. They also like cooler climates, which make them more common in northern regions or higher altitudes. Firs are typically pyramid-shaped and symmetrical, and most species range from 40 to 70 feet in height. Types of firs include the balsam fir, the noble fir and the subalpine fir. Interestingly, the most widely-known "fir" is not a true fir at all; the Douglas fir, while an evergreen, is of a different genus entirely.
Spruce Trees (Genus Picea)
Like the fir, the spruce produces single needles from its branches, but are distinguishable from firs in that the needles are four-sided rather than two-sided. The needles of many spruce tree species have a more bluish hue to them. Spruce can occur in a variety of soils and moisture levels, and are moderate- to fast-growing trees, sometimes reaching heights of over 140 feet. Common species of spruce trees are the Colorado blue spruce, the black spruce and the Norway spruce.
Other Types of Evergreens
Many common species of evergreen trees do not fall into the genus of pine, spruce or fir--for example, cedars, junipers and arbor vitae. These other evergreens can take a wide range of characteristics. The American arbor vitae, for instance, sports scalelike leaves rather than needles, and the famed sequoia (redwood) trees of the Pacific Northwest are the tallest trees in the world, reaching heights of several hundred feet and living for hundreds of years.