Ailanthus altissima (Mill.) Swingle (Family: Simaroubaceae)

Tree-of-heaven is a rapidly-growing deciduous tree that was introduced from China. It resembles a sumac or a hickory but can be easily distinguished by its large twigs with large leaf scars and the offensive odor given off by its leaves and flowers, which is reminiscent of rotting or burning peanuts. Tree-of-heaven can reproduce both sexually by seeds and asexually by vegetative sprouting. Established trees produce many suckers from their roots, resulting in dense stands. Trees that are cut down re-sprout vigorously from the stumps, making this tree one of the most difficult invasive species to control effectively. Fortunately, a good amount of research has already been conducted on the effectiveness of various control methods.

Also known as: Ailanthus, Chinese sumac, China sumac, stinking sumac, copal tree, varnish tree

Origin: Tree-of-heaven is native to central China. It was first introduced to North America in 1748 by a Pennsylvania gardener, and then in California by immigrants during the gold rush years. By 1840, it was commonly available in nurseries. It was widely planted in cities because of its ability to grow in poor conditions.

Description:

• Tree-of-heaven has smooth stems with pale gray bark and large chestnut brown twigs.

• Leaves are large and pinnately compound. They can be 1 to 4 feet in length and have about 10 to 25 leaflets each. Each leaflet has one or several glandular teeth near the base.

• Tree-of-heaven is a dioecious plant, meaning that male and female flowers occur on separate trees. Flowering begins in early summer. Flowers are small, yellow-green, and have 5-6 petals each. They occur in dense clusters near the ends of the upper stems.

• Fruit is produced on female plants in early fall. The fruits are papery, somewhat twisted, winged structures called samaras that are tan to pink in color. Samaras occur in large clusters with each containing a single central seed. Fruits may persist on the trees through the following winter.

• Each tree can produces hundreds of thousands of seeds in a single season.

• Tree-of-heaven roots have very aggressive rhizomes, allowing them to produce numerous suckers.

Habitat description: Our most aggressive, non-native tree, Tree-of-Heaven is found in a variety of disturbed environments. The ability to tolerate dry, wet, saline, fertile, and polluted environments make this a versatile competitor. Seedlings can be found growing out of cracks in sidewalks as well as competing with native hardwood tree regeneration in forest openings. In Brown County, trees are often observed growing along roadsides, right-of-ways and forest canopy gaps. Several dozen plants can be found about 1 mile North of Nashville on the east side of SR 135 just before the first rock-cut.

Distribution: Tree-of-heaven is now widely distributed in the United States. It is commonly found in disturbed urban areas, where it will sprout up just about anywhere, including alleys, sidewalks, parking lots, and streets. Away from cities, it is commonly found in fields, woodland edges, and forest openings. It is extremely tolerant of poor soil conditions; however, it is not shade-tolerant. Its seedlings have become an agricultural pest that pop up by the hundreds in recently planted fields.

Problem: Once tree-of-heaven has become established, it can quickly take over a site and form an impenetrable thicket. These dense clonal groups displace native species and rapidly take over natural areas. The plants produce toxins that kill other species or prevent them from growing in the first place. In cities, the aggressive root systems have been known to cause damage to sewers and foundations.

 Control: Elimination of tree-of-heaven requires diligence, due to its abundant seed production, high seed germination rate and vigorous vegetative reproduction. Targeting large female trees for control will help reduce spread by seed. Young seedlings may be pulled or dug up, preferably when soil is moist. Care must be taken to remove the entire plant including all roots and fragments as these will almost certainly re-grow.

Control: Tree-of-heaven may also be effectively controlled with herbicides such as triclopyr or imazapyr. They may be applied to the leaves, basal bark, cut stumps, or by the hack-and-squirt injection method. Basal bark application may be the easiest method, as it does not require any cutting. It will be most effective during the late winter or early spring. If trees are being cut and removed from the area, application to cut stumps will be the most useful. The hack-and-squirt method can help to minimize sprouting and suckering when applied during the summer.

USE PESTICIDES WISELY: Always read the entire pesticide label carefully, follow all mixing and application instructions and wear all recommended personal protective gear and clothing. Contact your state department of agriculture for any additional pesticide use requirements, restrictions or
recommendations.