ecause trees have such varied features, there are numerous ways to
classify them. They can be grouped according to the way they shed their leaves, how they
reproduce, how they grow, their internal structure, and the types of flowers and seeds
Gymnosperms and Angiosperms:
The broadest way to categorize trees is by their seed
development. Gymnosperms (JIM-no-sperms) are plants that have "naked" seeds --
seeds that are not enclosed in flowers or in fruit. In most gymnosperms, the seeds are
produced on the surface of the scales of female cones and are pollinated by wind. Conifers
-- such as pines, hemlocks, redwoods, spruces and firs -- are the most common types of
gymnosperms with more than 500 species worldwide.
Angiosperms (AN-gee-oh-sperms): Worldwide there are more
than 235,000 species of angiosperms, the only types of plants that have true flowers and
bear their seeds in fruits. In temperate zones, many angiosperms -- such as oaks, willows,
maples and birches -- are deciduous trees. In tropical zones, many angiosperms are
evergreens. These include palms, figs and southern magnolia. All flowering plants that are
not trees, such as tulips, blackberries and poppies, are also in this family.
Foresters often call broad-leaved trees
"hardwoods" because most broad-leaved trees have harder wood than do most
needle-leaved trees. For example, maples and oaks are known for their tough, hard wood and
are often used to make high-quality furniture and floors. Of course there are always
exceptions such as cottonwoods and magnolias, which are broad-leaved but have very soft,
lightweight wood. Softwood is used to describe needle-leaved trees such as pines and
spruces because most of them have softer wood than do most broad-leaved trees. An
exception is yellow pine, which is a needle-leaved tree but has very hard wood.
Deciduous and Evergreen
Trees that shed all of their leaves in the fall are
called deciduous, a term that comes from a Latin word meaning "to fall off."
Deciduous trees, such as oaks, maples, beeches and hickories, tend to have broad, flat
leaves that are more delicate than the leaves of evergreens. As their name implies,
evergreens maintain green leaves on their branches throughout the year. Instead of losing
all their leaves at once, evergreens constantly shed a small proportion of their older
leaves and replace them with new leaves throughout the year.