When identifying shrubs, a good look at the leaf, flower and overall shape of the plant will help in identifying the family and species of your specimen. However, if the flowers are not present, then the leaf will have to be your guide for determining species.
Determine whether the leaf sample is a needle or a true leaf. This a very basic step that separates the conifers from the flowering plants. Although conifer needles can be accurately described as modified leaves, the remaining discussion will centre on distinguishing the leaves of flowering plants, which is a very broad area of study, all in itself.
Look at the leaf to see if it is deciduous or evergreen. Evergreen leaves occur on some shrubs such as the holly and are characterised by a hard, shiny surface that is not very flexible and cracks easily. Once it is determined that an evergreen leaf is present, your selection of possible shrubs is greatly reduced.
Look at the veins of the leaf to see if the veins are parallel, as in a blade of grass, or net-veined, as in an oak or maple. This step separates the monocots from the dicots. Unfortunately, most shrubs fall into the latter category, which is quite large in number.
See how the leaf is attached to the twig and small branch. Your leaf will have either alternate or opposite attachment. If the attachment is opposite (two or more leaves attached on opposite sides of the twig), then you will have to take a closer look to see if the leaf is attached in pairs or whorled. Whorled refers to the circular attachment of three or more leaves at one point on the stem of the twig.
Check to see if the leaf is simple or compound. If just one leaf attaches to the woody twig by means of a soft petiole then the leaf is considered simple. Many trees, such as the birch, oaks, maples and beech, attach in this manner. If the leaves branch out from the woody twig in great arrays of multiple leaves, then this situation is described as compound. Sumac, mountain ash and Virginia creeper are examples of shrubs that have a compound leaf.
Look to see if the edge of the leaf is smooth or does it have teeth. This is another important leaf characteristic that you must identify.
See if the leaf is lobed like a maple leaf or if it's elliptical or round without any indentations along the edge.
Look again for unique characteristics, such as hair on the bottom of the leaf.
Crush the leaf to see if it has an aromatic smell. This is key to identifying sassafras, a common shrub of the eastern woodlands that smells like lemon when crushed in your hand.
Don't forget that shrubs have woody trunks or stems that almost always begin branching at or near ground level. Get to know the native shrubs of the area where you live. Get to know the favourite ornamental shrubs in the area where you live.
In some cases identifying the plant to species solely by the leaf characteristics may be very challenging.