Species: Ailanthus altissima

Although ailanthus is sensitive to frost damage during its early years (Adamik and Brauns 1957), 6-year-old trees have survived winters of -33 centigrades accompanied by high winds (Zelenin 1976). Although Koffer (1895) suggested that ailanthus was unable to withstand the prolonged dry seasons of the Midwest, Dubroca and Bory (1981) commented on the "drought resistance" of the species. Dry soils are probably more suitable for its growth than wet soils (Adamik and Brauns 1957). <br><br>Ailanthus does well on very poor soils. Adamik and Brauns (1957) cultivated the species on rather thin topsoil and it "thrives even on stony ground." The tree has been used in revegetating acid mine spoils, tolerating a pH of less than 4.1, soluble salt concentrations up to 0.25 mmhos/cm and phosphorus levels as low as 1.8 ppm (Plass 1975). The tolerance of ailanthus to soil salinity is a disputed point in the literature. Opinions range from "salty soils not suitable for growth" (Adamik and Brauns 1957) to ailanthus "growing well on very saline shell sands (Lavrinenko and Volkov 1973). Intermediate views are expressed by Brogowski et al. (1977), Semoradova and Materna (1982) and Zelenin (1976). <br><br>Ailanthus has been planted widely in urban areas because of its ability to tolerate atmospheric pollution. Its ability to adapt to "the dirt and smoke, the dust and drought of cities" was recognized nearly 100 years ago (Sargent 1888). More recently ailanthus has been observed to survive cement dust near cement and lime works (Klincsek 1976); it is moderately resistant to fumes produced by the coke and coal-tar industry (Kozyukina and Obraztsova 1971); its leaves absorb significant amounts of sulfur in areas of high traffic flow (Kim 1975); it can accumulate high levels of mercury in its tissues (Smith 1972); and it is somewhat resistant to ozone exposure (Davis et al. 1978). <br><br>Although ailanthus may suffer from root competition by other trees already established in an area (Cozzo 1972), usually it competes successfully with other plants (Cozzo 1972, Hu 1979) and is considered a "dangerous weed" in forest plantations (Magic 1974). A high degree of shade tolerance gives ailanthus a competitive edge over other plant species (Grime 1965). The production of toxic chemicals by ailanthus may also explain the success of this plant. An aqueous extract of ailanthus leaves has been shown to be toxic to 35 species of gymnosperms and 10 species of angiosperms (Mergen 1959). This may be important in limiting natural succession in ailanthus stands. The toxicity levels are highest in the leaves during the early part of the growing season and are maintained at high levels at least until October (Voigt and Mergen 1962).