Leaves come in many shapes, sizes, textures and shades of green. They are one of the first things we notice about a plant and one of the main identifying features, especially from a distance. As tools in plant identification, they need to be supported by flowers and fruit since similarly shaped leaves can be found in unrelated plants. Certain features such as placement of veins and pattern of leaf attachment to the stem are key characteristics.
One of the most obvious characteristics of a leaf is its shape. This can be narrow and sword-shaped, like a blade of grass, or oval, round or spear-shaped. Many are lobed, some terminating in sharp points, some with blunt or rounded ends. The parts may be divided into smaller lobes, giving a ferny effect. Instead of a whole leaf, six or more leaflets may be attached to the midrib, called a "pinnate" arrangement, or the leaflets may be attached to each other at the base, called "palmate."
Pay attention to the surface of the leaf, noting whether it is soft and velvety or somewhat waxy, dull or shiny, covered with hairs or finely ribbed. Turn the leaf over and look at the bottom. Sometimes there is soft down attached. Note the thickness of the leaf and its color. Often, if you're familiar with a plant, just the shade of green can let you identify it from a distance.
Plants in the group containing lilies and grasses have veins that run parallel to each other. These are called dicots, or dicotyledons. Monocots, or monocotyledons, have netted veins, like lace-work. Certain families have characteristic veining. Dogwoods, for instance, have veins that curve around the oval leaves to meet at the tip. Some plants, such as hostas, have prominent veins that give an interesting texture to the leaf.
The edge of a leaf may be smooth or toothed, finely or coarsely serrated. It may be wavy or lobed, crinkled or curled. It may also be edged with hairs.
One of the most important things to note about a plant's leaves is how they are arranged along the stem. Each group of species, in general, has similar leaf attachment patterns. They can be grouped together in whorls, paired in an opposite arrangement or placed alternately along a branch. Usually a small bud is found at the base of each leaf, pointed or rounded in shape.