This past Christmas I made evergreen centerpieces for my brother and sister using two different evergreen cones and branches found in my backyard. I learned that of the 1,000 tree species in the United States, several hundred produce cones whose leaves remain all year so they are called evergreens. This article will help you appreciate and identify four types of common evergreen trees: the pines, spruces, firs and hemlocks.
Evergreen ancestors date to 270-350 million years ago. Scientists think flying reptiles like the pterodactyl perched in trees resembling our present-day evergreens. These trees persisted because they could survive growing in poor soil, endure a short growing season, and live in a cold climate. Thick bark enabled them to survive natural forest fires.
The life cycle of evergreens is interesting because the male cones and the female cones appear in the same tree but on different branches. The small male pollen cones, often hidden in the needles, produce tiny pollen grains, the counterpart to a sperm. In the spring the male pollen cone releases thousands of mustard-colored pollen grains which cover nearby branches or automobiles. The female cone, the familiar cone seen on an evergreen tree, sits upright on a branch and contains the ovaries at the base of each cone scale. In the spring, the cone scales open, allowing pollen to settle on the scale. A liquid is extruded from the ovary, suspending the pollen grains, and both are retracted into the ovary. The cone scale closes, keeping the pollen inside. The pollen grows a tube, discharging a sperm to fertilize the egg in the ovary. The female cone grows in size, eventually becoming dependant due to the increased weight. After the eggs mature, usually in the late summer and early fall, the cone scales open up allowing winged seeds to drop to the ground or to be eaten by birds and rodents. The evergreens to be described have native growing ranges from Minnesota east across southern Canada and south into the northern United States and along the Appalachian Mountains.
Article Photos
Representatives from common evergreen groups — the pines, spruces, firs and hemlocks — are pictured with a typical branch and cone. Note the upright cone spike of the balsam fir, unique among evergreens.
Photo by Robert M. Ungerer
The white pine is a common example from the pine family. Needles four inches long are grouped in bundles of five, one for each letter in the name, ''white.'' Cones are five inches long and slender. The white pine is susceptible to two diseases: white pine blister rust kills by attacking the bark and white pine weevil kills the terminal bud at the top of the tree, as happened to the 10 white pine trees my father and I planted 25 years ago. A secondary sprout develops the next year, but the tree becomes bushy and stunted in height.
The Norway spruce, introduced from Europe, is common along highways and yards in New York. It is the only evergreen with drooping branches. Needles one inch long are like all spruces, sharp and prickly. Cones are 4-6 inches long. Since it grows rapidly, Norway spruce is useful for reforestation.
The balsam fir makes a good Christmas tree because the needles are fragrant and stay on the tree. Needles one-and-a-half inches long with round tips are soft to touch, unlike the spruce. The employees at Sunset Hill Cemetery in Lakewood trimmed a small balsam fir branch for me, pictured with this article, containing the typical upright two- to four-inch cones devoid of cone scales which fell off naturally, allowing the seeds to scatter. All other evergreen tree cones hang down.
Lastly, the eastern hemlock is a graceful tree often used to create a dense evergreen fence. Needles one-half inches are long and flat. The tiny cones are three-fourths inches long. As a Boy Scout, I learned to use dead twigs on the hemlock as tinder to start a campfire in the rain.
Borrow a tree field guide from the local library, approach the evergreen tree in your yard or neighborhood, and match up the needles and cones to learn the evergreen group or species name. From then on you can appreciate the tree's beauty and uniqueness knowing is not ''just another evergreen tree.''