Tree of Heaven: Accurate Identification

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- Tree-of-heaven, ailanthus altissima, often referred to as simply ailanthus, is a rapidly growing, exotic invasive tree native to Asia.

It was first introduced into the United States in the late 1700s, and has since become an aggressive, invasive species, that can quickly overwhelm roadsides, fields, and natural areas, displacing native plants.

Tree-of-heaven tolerates a wide variety of sight and moisture conditions, from fertile soils along rivers and streams, to rocky drought-prone soils on ridge tops and abandoned mines.

It is commonly found growing on disturbed sites such as roadsides, as well as forest edges, fence rows, and in forest openings.

Tree-of-heaven is a rapidly growing, relatively short-lived tree.

It can grow to a large size, with mature trees reaching 80 feet in height, and six feet in diameter.

Tree-of-heaven as pinnately compound leaves, meaning that each leaf has a central stem called a rachis, with multiple leaflets on both sides.

Tree-of-heaven leaves range in length from one to four feet, with anywhere from 10 to 40 leaflets.

This image shows the tree-of-heaven leaf next to a yardstick for perspective.

The margins or edges of each leaflet are smooth, or what is referred to as entire.

At the base of each leaflet you will find one or two bumps known as glandular teeth.

When crushed, the leaves emit a distinct offensive odor that can compare to cat urine or burnt peanut butter.

The bark of tree-of-heaven is light brown to gray, resembling the skin of a cantaloupe.

As the tree ages, the bark turns darker gray and becomes rough.

The twigs of tree-of-heaven are alternate on the tree.

They are stout, greenish to brown in color, with small lateral buds, and lack a terminal bud at the end of the twig.

The twigs have large V or heart-shaped leaf scars.

The leaf scars, they are exposed when the leaf falls from the stem.

Lateral buds are located at the top of each leaf scar as seen in this image.

The twigs can be easily broken to expose the large spongy brown center or pith.

It admits the same unpleasant odor as the crushed leaves.

Tree-of-heaven is dioecious, which means a tree is either male or female, and grows in colonies or clones.

All trees in a single clone are the same sex.

Seeds form on female trees in a one or two-inch long twisted samara or wing.

There's one seed per samara.

The samaras are found in clusters, which remain on the tree through much of the winter.

Individual samaras eventually fall to the ground, assisted by gravity and wind.

To summarize, the distinguishing characteristics of tree-of-heaven include pinnately compound leaves, leaflets with smooth edges and glandular teeth at the base, distinctive unpleasant odor, bark resembling the skin of a cantaloupe, stout greenish brown twigs that have a spongy brown pith, and seeds in twisted samaras that remain on the female trees into the winter.

By using these key characteristics, you will be able to identify tree-of-heaven on your property, as well as across the landscape.