Tree of heaven (Ailanthus altissima) is a member of the Simaroubaceae family. The native range for this tree species is central China. In 1784, a gardener from Philadelphia, PA purposefully introduced tree of heaven to use as an ornamental plant. Chinese immigrants during the gold rush era of the early 1800s also brought tree of heaven to the United States and by the 1840s it was readily available from nurseries. The habitat of tree of heaven in the U.S. varies greatly from city streets to abandoned mine sites. Currently it is found in 30 states from east coast to west coast (Swearingen and Pannill 2009).
Tree of heaven is a deciduous tree that can obtain a height up to 80 feet (25m) and 6 feet (1.8m) in diameter. The leaves are arranged alternately and are pinnately compound. Leaves can become very large, 1 to 3 feet (30 to 90cm) long and contain 10-40 leaflets (Miller 2004). The leaflets are located on reddish-green stalks and are entire except for one or more coarse teeth near the base, each with a large gland underneath. The bark of tree of heaven is smooth and gray in color. Tree of heaven is also dioecious, meaning that male and female flowers occur on separate trees. The flowers are green to greenish yellow, twisted and the fruits are winged seeds, or samaras (Gleason and Cronquist 1991). Anything easily identifiable characteristic is the bitter smell (often compared to rotten peanut butter) that is produced when the leaves are crushed.
Many characteristics that enhance a plant's ability to successful establish populations in new territory are possessed by tree of heaven. Tree of heaven are capable of surviving in highly disturbed areas in urban and rural settings. Two different reproduction strategies are used by tree of heaven: vegetative propagation and seed production. Asexual reproduction or vegetative propagation occurs by one tree producing identical copies of itself in the form of root suckers. Seed production is very prolific and the samara is winged and easily distributed by the wind. Another strategy used to out-compete native plant species is the production of allelopathic chemicals (inhibit one plants growth through the release of toxic chemicals). Ailanthone is a chemical exuded by the roots of tree of heaven that is toxic to other species, serving as a natural herbicide (Heisey 1996).
There are native species that look similar to tree of heaven and include: hickories (Carya sp.), sumacs (Rhus sp.), walnut (Juglans sp.), and ash (Fraxinus sp.) (Miller 2004). If unsure about the species, crush some leaves and do a smell test. You will surely be able to identify tree of heaven that way!
Currently at New River Gorge National River, tree of heaven is treated with herbicide in special biological and cultural areas. A basal bark treatment using triclopyr is the most common method for killing tree of heaven.
Heisey, R.M. 1996. Identification of an allelopathis compound from Ailanthus altissima (Simaroubaceae) and characterization of its herbicidal activity. American Journal of Botany. 83(2): 192-200.
Gleason, H.A. and A. Cronquist.. 1991. Manual of Vascular Plants of Northeastern United States and Canada. 2 ed. Bronx (NY): The New York Botanical Garden Press, p. 355.
Miller, J.H. 2004. Nonnative invasive plant of southern forest: A field guide for identification and control. General Technical Report SRS-62. U.S. Forest Service Southern Research Station, Asheville, NC.
Swearingen, J.M. and P.D. Pannill. 2009. Plant conservation alliance's alien plant working group. Least Wanted: Tree-of-heaven. Available from https://www.nps.gov/plants/alien/fact/aial1.htm (accessed 21 March 2013).