Introduction to trees
Importance of trees: Trees have been called the structural elements of the ecosystem. They form the most noticeable living objects except in the driest and coldest climates. Trees have whole communities of other organisms associated with each type. Some birds or insects are found only in broad-leaved trees, others in conifers. In addition, trees form levels in which these communities of other animals are found. Blackburnian Warblers are found at the tops of trees, Canada Warblers lower down. Nuthatches, Brown Creepers, and Woodpeckers are typically found on the trunks and larger branches.
Most botanists define trees as woody plants having a single stem and growing at least 10 feet tall — the height of a basketball goal. Other definitions are used, but they are similar. A shrub or bush, on the other hand, is a woody plant having multiple stems growing from the same roots (Also check our Fig tree root guide) and is usually lower growing. An oak is a tree. Most lilacs are shrubs. At the other end, trees can be gigantic. Some species, like Giant Sequoias, Coast Redwoods, Douglasfirs, and some Eucalyptus, grow 300 feet tall or more and have trunks 30 feet across. Some species also have very long life spans. The Great Basin Bristlecone Pine often lives longer than 4,000 years.
That’s right, four thousand. Some trees living today are as old as the most ancient pyramids of Egypt. They were living when civilization began in the Indus Valley and the earliest dynasties of China were founded. These trees were unimaginably ancient when Troy fell to the Greek invaders. More than half their lifetime had passed by the time Christ was born. The Norman invasion of England, the Viking discovery of North America, and the Mongol Empire are recent history to them. Whole forests of several species are alive now that were old when the first permanent European settlements in the new world were founded.
Different kinds or species of trees can be told apart in many ways, some of them available to the blind. The feel of the leaves, twigs, and bark varies from species to species. Some trees have distinctive odors. Even the sounds the wind makes in the trees can be different depending on the kind of tree. And some birds are heard in one kind of tree, but not in others.
While the general concepts in this brief introduction are accurate for most parts of the world, the specifics here deal with North America.
Trees, in some form or another, have been around for a lot longer than we have. The first plants to meet the general definition of trees were probably the giant tree ferns which are now rare, but were common enough during the Carboniferous Era to form the coal and oil deposits we now use.
Most trees, as we commonly think of them, fall into one of two groups which we can call coniferous and broad-leaved. Most, but not all, conifers produce their seeds in woody cones, exceptions being the junipers and yews, and don’t really have what we think of as flowers. Most, but not all, broadleaf’s produce their seeds in more fleshy fruits, and have flowers, even though many of the flowers are quite small. The conifers evolved before the broadleafs; flowers didn’t appear in the world until many millions of years after the appearance of trees.
The easiest way to tell the broadleafs from the conifers, for either a blind or a sighted person, is by the shape of the leaves. For the most part, leaves of conifers and smaller and narrower than the leaves of broadleafs, thence the name ‘broadleaf’. In North America, most conifers retain their leaves during the winter. Exceptions are the Larches and the Baldcypress. Many, but not all, broadleafs lose their leaves in the winter. The chlorophyll in the leaves is what gives them their green color, so when that is no longer produced, the other colors that were present all along come through and the leaves change color. A layer forms between the leaf stem and the twig to protect the tree from moisture loss, and then the leaves fall.
The easiest way for a blind or low vision person to begin the identification of trees is to hold branches in his or her hand. On young trees, or those with low branches, that is easy. Otherwise, you may need help.
The first thing to decide is whether the branch is from a conifer or a broadleaf. For the most part, native broadleafs have much wider leaves than do conifers. Conifer leaves are small and narrow or needle-like, or even flattened to the twig like the scales of a fish.
In telling conifers apart it is important to note how the leaves grow and what shape they are. Some of these distinctions take a great deal of practice to learn. Don’t be discouraged; tree identification can be tough for sighted persons, too. If the leaves are flat and grow singly, then the tree is most likely a fir, hemlock, yew, or baldcypress. If they are rounded and grow singly, the tree is probably a spruce. Some spruce needles are very sharp and stiff, so be careful not to get stabbed.
If the needles grow in groups directly from the twig, the tree is a pine. Pines can be told apart by counting the number of needles.
Larches or tamaracks are more difficult. On young growth, the needles grow singly, but on older growth they grow in groups from woody pegs. Larches lose their leaves in the fall.
Scale-like leaves are found on junipers, what we call cedars, cypresses, and some other small groups. Practice is necessary for anyone who wants to learn trees. But you already know something that most people don’t — not all conifers are pines. I don’t know how many times I’ve seen motels or other businesses called ‘The Pines’ when the place is surrounded by spruces or firs while there isn’t a pine for miles.
Once you have decided that a branch comes from a broad-leaved tree, the next thing to do is to decide whether the leaves and small twigs grow opposite to each other on the twig or whether they alternate along the length of the twig. This is often difficult to do; don’t be happy with finding just one example on the branch; find several. It is important to do so because trees can be variable in their growth. In the winter, look for small twigs or for the buds that will become leaves next season.
If the twigs or leaves grow opposite to each other, the tree is in the maple, ash, dogwood, honeysuckle, or horsechestnut families. Next, decide if the leaves are simple or compound. Of course, you cannot do this in the winter. Other, more difficult cues are needed then.
A compound leaf has a stem originating from the branch and leaflets growing off of that. The best way to tell a leaf from a leaflet is to see if there is a bud where the stem grows out of the branch it is on. If so, it is a leaf; if not, it is a leaflet. This doesn’t work in spring before the buds form. However, this identifier is good for the summer and fall.
Among trees with an opposite growth form, the dogwoods and honeysuckles are generally small and have leaves with smooth, or only slightly jagged or toothed edges. Maples have leaves with deep cuts in them. Ashes and horsechestnuts (native North American horsechestnuts are called buckeyes) have compound leaves. The horsechestnuts or buckeyes have leaflets growing out in all directions from the end of the leaf stem like the fingers of a hand. Ashes have leaflets growing along the sides of the leaf stem.
If the tree is a broadleaf and has an alternate growth pattern, life gets tough. More than half of the seven or eight hundred species of trees (depending on who’s doing the counting) in North America fall into this group. The best thing to do is to find out what you have in your area, and then ask questions. Learn how to distinguish among the important groups, first. In some areas, such as the northeast United States, the oaks are fairly easy to tell from other groups. In some places, it is magnolias; others, poplars. If you can get at the tree itself, the smooth, but peeling bark of some birches is a clue. The smooth bark of beeches may be helpful.
In getting started learning the trees, find out what is around you, and don’t hesitate to ask questions. Don’t worry about making a pest of yourself; people who really want to learn something need to keep at it. If you learn the little bit of material on this page, you will be way ahead of most people. Look for nature programs in your area. Check with local Audubon chapters or groups serving the blind. Ask what is available and how to get something offered. If there is any way NHEST can help, call or write. Our address and phone number is below. And don’t give up just because you can’t identify something. I’ve been at this for years and have full vision, and I still make mistakes.
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- Evolutionary history
- Tree Identification
- Broad-leaved trees
- Getting started
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