Tree-of-heaven (Ailanthus altissima) is highly invasive and should not be planted in Ohio. Tree-of-Heaven is a highly invasive tree that is native to China. It was brought to this country in the early 1800s as a source of food for silkworms, which were simultaneously imported from the Orient. Although raising silkworms was a failure, the Tree-of-Heaven remained. This tree is often found in urban areas and thrives in disturbed and neglected sites where polluted conditions and poor, rocky soils prohibit anything but weeds to grow. Tree-of-Heaven is fast growing, and mature trees can produce in excess of 300,000 wind-dispersed seeds per year. Tree-of-Heaven frequently colonizes disturbed sites in Ohio woodlands and suppresses the growth of native trees. Trees found in the open may reach 80 feet tall by 40 feet wide and have a bold year-round texture. Its common name refers to its ability to reach even greater heights under optimum conditions in the Orient, not to any aesthetic or horticultural qualities. As a member of the quassia family, it is related to other genera in the family which mostly reside in tropical locations, some members of which provide substances used in medicines, insecticides, and dyes. Tree-of-Heaven may suffer from verticillium wilt, especially in wet springs in poorly drained soils, and a few other minor diseases and pests, none of which are significant. It is often eventually cut down or severely pruned because it gets too big for the site from where it sprang, or the property is bulldozed for a new construction project. Tree-of-Heaven has the largest pinnately compound leaves of any tree found in Ohio. Kentucky coffeetree has bipinnately compound leaves, and the walnuts’ are not as long. The alternate leaves emerge bronzed in spring and quickly transition from medium to dark green as they expand to about two feet in length, with an even number of leaflets. Crushed leaves and stems emit an unpleasant odor. Fall color is essentially non-existent in Tree-of-Heaven. Tree-of-Heaven has relatively long, green-white flowers in late spring, which often go unnoticed because of their ultra-thin character and the fact that they are often lost amongst the overpowering foliage. Male flowers have a vile scent, while female flowers have no odor. Male and female flowers usually occur on different trees making this species primarily dioecious, which becomes evident by mid-summer when the huge clusters of fruits dot the canopy of female trees. Composed of many individual samaras or winged seeds, the fruits stand out in the Tree-of-Heaven canopy because they have a light green, yellow, orange, or red color in summer, then change 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. When the twigs or leaves of Tree-of-Heaven are crushed, they emit a slightly foul odor. The bark of Tree-of-Heaven remains fairly smooth as the twigs become branches, taking on a subtle checkered appearance. Even as this species attains great heights and trunk diameters, hints of ridges and furrows are slow to appear on the light gray, mature bark.