Nine different species of magnolia trees exist in the wild in North America, according to the "Trees of North America." These trees produce fragrant and large showy flowers as well as elongated cones of berrylike fruits. All of the magnolias are native to the eastern half of the United States, with the ranges of several types overlapping. The leaves of magnolia trees can be a great aid when it comes to trying to tell one type from another.
Measure the size of magnolia leaves. Some, such as bigleaf magnolia, are as long as 30 inches and as wide as 10 inches. Other magnolias with exceptionally large foliage include species such as the umbrella magnolia and Ashe magnolia. Magnolias with leaves in the 10-inch long range include the Southern magnolia, Fraser magnolia and cucumber tree. The sweetbay tree, yellow magnolia and pyramid magnolia have smaller leaves, about 5 to 6 inches in length.
Inspect the shapes of magnolia leaves. The yellow poplar has the nickname of tuliptree, in part because the leaves have the shape of a tulip flower's unmistakable silhouette. Southern magnolia have oval leaves with a short point on the tip, and those of pyramid magnolia taper to a more pronounced point on the ends. The tips of bigleaf magnolia have a rounded appearance or, at the most, a blunted tip.
Examine the colors of the upper sides and lower sides of magnolia leaves. Sweetbay have shiny green leaves above, with the lower side a whitish hue. Pyramid magnolia leaves are a yellow-green on top, but a paler shade of that below. The cucumber tree has green leaves, but the undersides are pale compared to their upper surface. The fall colors of magnolia leaves are also useful in recognizing individual species. The "National Audubon Society Field Guide to Trees" says that yellow poplar leaves go yellow in autumn. Other magnolias lack vibrant fall color, such as the cucumber tree, which simply turns brownish-yellow.
Watch if magnolia leaves remain on the tree or fall off to help decide what species to which they belong. The Southern magnolia is evergreen, with its leaves staying on year round. The leaves of sweetbay, in the northern portion of the tree's range, fall off in autumn, but stay on the branches until spring when new ones grow in where the tree grows in the Deep South. The rest of the magnolias are deciduous, dropping their foliage in the fall months.
Look at other aspects of magnolia leaves. The leaves are alternate, meaning a single individual leaf develops at each node on the branch, not two opposite each other as in many other kinds of trees. The leaves will have smooth edges rather than toothed serrated margins. The texture is often leathery, and the leaves are typically thick. Magnolia leaves will gather under the tree and take a long time to decompose.