Leaves come in all types with different shapes and sizes. Depending on the type of tree, leaves can have different arrangements on the branches, different types of edges, different shapes and different arrangements. Although there several different ways to broadly classify the different types of leaves, each characteristic makes each type of leaf unique.
The edge of a leaf, also known as the leaf's margin, can come in several forms. One type of edge is an entire edge. An entire edge has a completely smooth edge with no ridges. Another type of edge is the toothed edge. Toothed edges can have a singly-toothed shape known as a dentate leaf, or a doubly-toothed edge known as a serrate leaf. Leaves with a lobed edge make up the last type of edge. A lobed edge divides the leaf into either small or large lobes with smooth edges.
Another way to classify different types of leaves uses the shape of the broad part of the leaf, known as the blade or lamina. One type of shape is the cordate shape. Cordate leaves have a triangular shape with a broad base and a pointed tip. Elliptic leaves have an overall elliptic shape, but the proportion of width to height can vary as long as the leaf has more height than width. Acicular leaves are shaped like needles; pine trees have acicular leaves. Hastate leaves resemble lobed leaves, but have three lobes that end in a point instead of a rounded edge. Ovate leaves have a similar shape as cordate leaves except that the tip is round instead of pointed.
The types of leaves can also vary in their arrangement. Leaves have two overall types of arrangements: simple and compound. Simple leaves are individually attached to the stem with one blade and have an independent vein structure. Compound leaves consist of many smaller leaflets that attach to the main leaf stem. The leaflets all have an identical shape. Leaflets can have one of two arrangements on the leaf stem depending on the type of tree. In an alternate arrangement, the position of the leaflets occurs at varying points along the stem so that no two leaflets are on the same level. In a opposite arrangement, leaflets occur in pairs that oppose each other along the leaf stem. The number of pairs of leaflets depends on the type of tree. Simple leaves also have similar styles of alternate and opposite arrangements on the branch or twig of the tree.