Natural History: Tree-of-heaven is a deciduous tree native to China. The species was apparently introduced into America by two different routes. The first route was through Pierre d'Incarville, who mistook it for the lacquer tree in China and sent seeds to England around 1751. It was then introduced to America by a Philadelphia gardener in 1784. Because of its rapid growth and ability to grow in unfavorable conditions with little care, it became a common stock in eastern nurseries by 1840. The second route was through Chinese miners. During the days of the California gold rush, many Chinese miners brought ailanthus seeds with them as they settled in California, probably because of its medicinal and cultural importance to them. Tree-of-heaven is tremendously tolerant of drought, poor soils, and air pollution, surviving in urban landscapes where no other tree can.

Identification: Tree-of-heaven has long, pinnately compound leaves which look somewhat like black walnut leaves. The easiest way to tell them apart? Crush some leaves � the telltale peanut butter smell of tree-of-heaven is very distinctive. The tree is dioecious, with male and female flowers on separate trees. In June, female trees are quite obvious as yellowish- red fruits dot the green tree canopy. The fruits turn to a beige color by early winter and remain on the female trees until early spring. The stout twigs of tree-of-heaven have an olive-tan color in winter, with huge leaf scars and very small buds, with no true terminal bud. The bark of tree-of-heaven remains fairly smooth as the twigs become branches, taking on a subtle checkered appearance.

Reproduction: One mature tree-of-heaven can produce up to 350,000 seeds per year. These seeds are easily airborne and can be transported by water and birds as well. Germination of seeds is quite high. Mature trees also reproduce extensively by sending up root suckers and sprouts from cut stumps. Sapling growth can reach 3-4 feet a year, faster than any of our native tree species.

Range and habitat in Indiana: Tree-of-heaven has a long history in Indiana. John Merle Coulter, an early Indiana botanist, reported it had already escaped cultivation in five counties in central and southern IN by 1899. In Charles Deam�s 1940 Flora of Indiana he reported established populations in 13 counties scattered around the state. According to Bill and Edith Overlease in 100 Years of Change in the Distribution of Common Indiana Weeds (2002, unpublished report), it is now established in all counties in Indiana. It does well in a wide range of soil conditions, but appears to do particularly well in alkaline soil areas like the bluffs along the Ohio River and sand dune areas near Lake Michigan.

Impacts: It does best and establishes first where disturbance has increased the available light in a forest area � along roadsides, trails, or in canopy gaps - but once established it will move into undisturbed forest. Generally, it will not dominate in undisturbed forest but will simply hold on until windthrow, icestorms, timber harvest, or other disturbance introduces more light. Then it quickly fills all available gaps, elbowing out any native trees in the area. Tree plantations are particularly vulnerable to tree-of-heaven, which outgrows all of the planted trees and forms a pure tree-of-heaven forest.

Tree-of-heaven roots give off a toxin that acts as a herbicide that can kill or inhibit the growth of other plants, which may also explain its success at outcompeting native species.

Control: Young seedlings may be successfully hand-pulled if the entire root system is removed. However, if small portions of the root system are left, regeneration is likely. Use this method for seedlings under 3 feet tall when the soil is soft (after rain). For larger trees, cutting alone is not effective since this merely stimulates aggressive root suckering and stump sprouting.

It is of utmost importance to kill the entire root system. Systemic herbicides such as Roundup� or Glypro�  may be effective as a foliar spray on seedlings. For larger trees, cut stump treatment or basal bark application using a systemic herbicide such as Garlon 4� is best especially if treated in late winter or late summer. Always follow label directions when using herbicides.

Additional information: http://tncweeds.ucdavis.edu/esadocs/documnts/ailaalt.html,