Leaf Patterns
All about Leaf Patterns
Leaf patterns, along with size, flowers and overall form are among the many ways used to identify plants. Leaves are one of the first means of plant identification because they are on the plant for most if not all of the year. Flowers come and go often, sometimes with very short blooming times.
In order to identify leaf patterns, it is necessary to recognize the three parts of a leaf. They include the blade, which is the widest and most visible part and the stalk, which also is known as the petiole, and attaches the blade to the stem. The third part, the bud, is located where the stalk joins the stem.
When searching for leaf patterns, one of the first things to decide is whether the plant has broad or narrow leaves. Broad leaves are not only wide, but they also may have a system of veins that are quite visible to the naked eye. One example of a plant with this type of leaf is a maple tree. Narrow leaves can be needles or scale-type leaves. Examples of these kinds of leaf patterns are the pine tree and the Western Red Cedar, respectively.
Leaf patterns also involve how the leaf is attached to a stem or twig. An alternate pattern means that the leaves alternate from one side to the other along the length of the stem. An opposite pattern means that the leaves are directly across from one another on the stem. An example of a tree with an alternate leaf pattern is the American Elm, while the opposite pattern can be seen on the Common Boxwood. Many times more than two leaves may come from the identical location. These types of leaves are known as whorled.
Simple and compound leaves are much like they sound--the simple has one blade and the compound has more than one blade. A Red Maple has a simple leaf pattern, while the Paperbark Maple is an example of a tree with compound leaves. There are many different kinds of compound leaves, but the two most common are palmately compound and pinnately compound. The palmately type of leaf has leaflets on the end of the stem. There are usually three or more of these. The pinnately type of compound leaf has a number of leaflets as well, but these are spread out along the stem.
Often leaf patterns take into account whether or not the leaves have lobes. An example of a leaf with a lobe is the one on the Bigleaf Maple. The Eastern Redbud tree is a good example of a leaf without a lobe. The leaf margin, or area around the outside of the leaf, also is included in any description of leaf patterns. These can be smooth and round or toothed in several different variations. When trying to identify a plant, other things to consider are its overall shape, the vein pattern, the shape of the base and apex, the kind of smell it has, and whether the leaves are smooth or rough.