In order to identify a plant, there are several leaf characteristics that must be noted. First is the overall shape. Some plants’ leaves have very distinct shapes and can be used alone to identify the plant. Most, though, are similar to those from other species of plants. Therefore, more information is usually needed. Leaf type is a major factor.
They fall into two general types, simple and compound. Simple leaves grow separately, one to each stem, while compound grow in a series of smaller leaves called leaflets. Plants with the compound type often have a “fern-like” appearance. Leaf arrangement is the next factor to take into consideration. Some have opposite arrangements, meaning that they grow directly across the stalk or branch from each other. An alternate arrangement means that leaves grow in intervals on each side of the stalk. Whorled arrangements consist of several leaves growing from the same spot on the branch.
Color can only be used to identify plants on some occasions. Many change color with different levels of sunlight or in different seasons. However, some plants’ leaves have very distinct coloration. In these instances, color is a good tool to use in identifying plants using their leaves. Margins are one of the most helpful indicators of plant variety. The term margin refers to the contour of the leaf. An entire margin indicates that the contour of the leaf is smooth all the wall around. A lobed margin means that the leaf has rounded protrusions, as on an oak tree. A serrate margin features saw-like teeth, much like a serrated kitchen knife.
Last, a dentate margin indicates that a leaf displays sharp protrusions like long teeth. The final indicator of leaf origin is its odor. Like color, odor is sometimes not a particularly helpful tool. Some plants are nearly odorless, and many smell very similar. However, sometimes odor is the most clear indicator available. A good example of an extremely odorous plant is the eucalyptus tree. The eucalyptus has an extremely strong and distinctive smell. Someone familiar with the tree could likely identify it while blindfolded with just one sniff.
However, it is important not to rely too heavily on the sense of smell, because some plants mimic others in their scents! Using all of these factors, pant identification should be quite simple when observing the characteristics of leaves. It is sometimes easy to get confused by focusing too heavily on one or two factors, so it is important to look at the whole picture.