Simple Leaves: Lobed and Unlobed

Among trees, there are two main types of leaves: simple and compound. Simple leaves are those that have an undivided blade (the flat part of the leaf where photosynthesis occurs), while compound leaves have blades that are divided into multiple leaflets, each of which is attached to the same middle vein.

Simple leaves can be further divided into two categories: lobed and unlobed leaves. Lobes are projections of the blade with gaps between them (these gaps, however, do not reach the middle vein). Maple leaves, with their distinct pointed projections, are good examples of simple lobed leaves.

Unlobed simple leaves have plain, rounded shapes without any projections. Certain oak leaves, including those of the shingle oak, are good examples of this type of leaf.

Once you know that you are looking at a simple leaf, you can inspect its shape and other features to make a species identification.

Key Takeaways: Lobed and Unlobed Leaves

• There are two types of simple leaves: lobed and unlobed. Lobed leaves have distinct rounded or pointed projections, while unlobed leaves do not.

• Some lobed leaves are pinnate, meaning the lobes are located along a central axis, while others are palmate, meaning they radiate from a single point.

• Leaf lobes have their own veins, which connect to the midrib of the leaf.

Unlobed Leaves

Unlobed Leaf. Unlobed Leaf

The edge of a tree leaf is known as its margin. Unlobed leaves are those that lack significant projections. This does not mean, however, that the margins have to be completely smooth. Some unlobed leaves have small serrations called teeth, including the leaves of the sugarbud and the American elm. Others have a slightly "wavy" or sinuous leaf margin, such as the leaves of the persimmon. Still others have simple leaves whose margins are indeed quite smooth, including the leaves of the sassafras and eastern redbud. These leaves are said to have "entire" margins.

One of the most well-known trees with unlobed leaves is the flowering dogwood, which grows throughout eastern North America and in parts of northern Mexico. The tree is famous for its pink and white bracts (a type of modified leaf) and is a popular ornamental variety. In 1915, when Japan famously donated cherry trees to Washington, D.C., the United States sent 40 dogwood trees to Japan.

Another famous tree with unlobed leaves is the magnolia, which grows in North America, Central America, and Southeast Asia. Magnolia leaves have a waxy sheen on one side and a matte texture on the other. The magnolia is the official state flower of Louisiana and Mississippi. Some parts of the magnolia—including the flower buds—are used in Asian cuisine and in traditional Chinese medicine. The magnolia is named after Pierre Magnol, a French scientist who invented a classification system for plant families based on their physical characteristics.

Lobed Leaves

Lobed Leaf. Lobed Leaf

Lobed leaves are those that have distinct projections from the midrib with individual inside veins. Some lobe ends are rounded, such as those of the white oak, while others are sharp or pointed, such as those of the northern red oak or the sweetgum.

Some lobes are pinnate, which means that they are arranged along a central stalk. Other lobes are palmate, which means that they radiate from a single point (and resemble a set of fingers and the palm of a hand). The number of projections on a single leaf varies from species to species.

One of the most famous plants with lobed leaves is the dandelion, which grows throughout Europe and North America. Though best known for its bright yellow flowers, the plant also has distinct pinnately lobed leaves whose projections vary in size and texture. These leaves can grow over 10 inches long. The dandelion is also unique in that the whole plant—including leaves, stems, and flowers—is edible; it is used in Chinese, Greek, and Indian cuisine.

The common hops plant, whose flowers are used to brew beer, also has lobed leaves. Unlike the leaves of the dandelion, the leaves of the hops plant are palmately lobed. Varieties of hops are cultivated in Europe and North America, with important production centers in Germany, the Czech Republic, and Washington State. Though primarily used to add bitterness to beer, hops are also used in other beverages, including teas, and in herbal medicine.