Ailanthus
(Tree of Heaven)

Where it originates:

Originally from China, Ailanthus seeds were brought to Europe believed to be Lacquer tree seeds, and then distributed to the new world shortly after in 1748. Despite the mistake Ailanthus became a common nursery plant due to its ability to grow fast with little or no care; characteristics that also allowed it to escape from cultivation easily. In its native range it grows out of high mountain rocks where no other trees can survive, which is where it got its name – Tree of Heaven.

Identification:

Ailanthus leaflets are lance shaped, with 1 to 5 teeth at each base (see photo to right). These leaflets, which may number 11 to 41 on a stem, make up a single compound leaf. Native sumac trees can look similar to Ailanthus, but will typically have teeth along the entire leaflet margin, or none at all. If you’re unsure whether you’ve found a specimen, grab a leaf and break it up with your fingers. Ailanthus has a characteristic foul odor, compared to rancid peanut butter or burnt popcorn.

Bark is smooth, light gray to brown when trees grow larger. Yellow flowers appear in clusters at the end of branches in early summer, and a single tree can produce more than 300,000 wind dispersed seeds in late summer. Tree sexes are separate, with male and female flowers appearing on different trees, and only females producing seeds.

Habitat:

Today Tree of Heaven is distributed from Massachusetts to Oregon, and from Toronto to as far south as Argentina. It’s an incredibly prolific seed producer and its ability to tolerate poor soil and pollution make it extremely adaptable. Ecological disturbance created by cities offer ideal habitat for Ailanthus to flourish, and roads serve as perfect migration routes. You’ll find it in sidewalk cracks, in cleared and neglected sections of farm fields, vacant parking lots, or along rail lines.

Ecological Impacts:

Once established, these trees can form dense stands that are extremely hard to remove, and that push out native species. Ailanthus also produces noxious chemicals that have shown to be toxic to at least 45 other plant species, and that give it a competitive edge by preventing natural succession.

Control: 

Simply cutting Tree of Heaven will only cause a burst of new sprouting. Often the best control option includes both mechanical and chemical treatment, such as the hack-and-squirt or girdling method. Treatment must be done repeatedly year after year to deplete the roots, and the seed bank.
Girdle trees by scraping off the outmost layer of bark in a ring around the trunk so that the yellow cambium is exposed (this can be done with a hatchet or paint scraper). Follow up with this by immediately painting on herbicide such as glyphosate with a paint brush. This is a very effective way of killing the trees, while limiting the amount of herbicide released into the environment.

References:

Hoshovsky, Marc. "Ailanthus altissima." Element Stewardship Abstract (1988): 13.

Kaufman, Sylvan. Invasive Plants. 1st. Mechanicsburg, PA: Stackpole Books, 2007. 95-98. Print.

Miller, James. Nonnative InvasivePlants of Southern Forests. Asheville, NC: Southern Research Station, 2004. Print.

Photos in order of appearance from top to bottom:
(Chuck Bargeron, University of Georgia, Bugwood.org), ( Chris Evans, River to River CWMA, Bugwood.org), ( James H. Miller, USDA Forest Service, Bugwood.org), (Chuck Bargeron, University of Georgia, Bugwood.org)