Tree of Heaven (Ailanthus altissima)
Tree-of-heaven (also called ailanthus, Chinese sumac, stinking sumac, stinktree, and stinkwood) is a non-native, invasive tree species from Asia. It has spread throughout this country where it is a nuisance in rural and urban communities alike. This thicket-forming species can grow up to 20 feet in a year and can attain a height of eighty feet and a diameter of three feet. It has now become a serious ecological and economic threat to our native forests and waterways and an eyesore in urban areas. It can also take over disturbed sites around oil and gas wells, in old pastures, along forest edges and fencerows, and in woods that have been heavily cut over. Ailanthus has no timber or wildlife value—it doesn’t even make good firewood. This very hardy and invasive tree also produces chemicals that suppress and kill nearby native vegetation growing under and around it, resulting in tree-of-heaven thickets that become somewhat open.
Tree-of-heaven was first imported from China to industrializing Europe in the 1740’s for its tolerance to pollution and its fast growth. In 1784, tree-of-heaven was introduced to America by a gardener in Philadelphia. At the same time, this tree was also brought into California by Chinese miners. Because of its durability and fast growth, it quickly became popular as a shade tree in the developing world. However, it didn’t take long for enthusiasm to wane with this tree’s foul smell, prolific seeds, weak wood and sprouting habit. Today tree-of-heaven is rarely planted, but can be found in all Ohio counties along waterways, roads and forest edges. It is officially designated a noxious weed in Australia, the US, New Zealand, and just about all of Europe.
Stout-twigged Ailanthus in foreground and shorter sumac in background with upright red seed heads.
What does Tree-of-heaven look like?
Tree-of-heaven has smooth gray bark that becomes rough and fissured with age. It has very stout twigs, and compound leaves. All parts of the tree-of-heaven have a strong disagreeable odor; especially the male flowers, crushed leaves, and cut or bruised stems.
Many people confuse tree-of-heaven with the native species walnut and sumac. Both walnut and sumac have saw-toothed leaflets while the leaflets of tree of heave are smooth-edged with the exception of a few small teeth near the base.
A small gland bump is present at the tip of each tooth on the underside of the leaflet. This gland is an identifying characteristic that distinguishes the tree-of-heaven from sumac and walnut. The female tree-of-heaven can be identified by clusters of bright red papery seeds which form in late summer and early fall and turn brown and hang on the trees over winter. Sumacs have upright clusters of red berry-like seeds. These bright red seed heads are a stark contrast to the wind-dispersed papery seeds of tree-of-heaven. Sumacs excrete a milky sap when a leaf is picked. Tree-of-heaven leaves do not have milky sap.
How do I control Tree-of-heaven?
In other tree species, girdling or cutting down a tree is enough to kill it. This is not true with tree-of-heaven. Cutting without the use of herbicides actually stimulates the growth of sprouts from stump and roots. Where there was one tree, countless sprouts will emerge potentially creating an even bigger problem. You may be able to slow ailanthus with intense and continuous manual efforts (i.e., cutting and pulling), but in most cases, this tree cannot be effectively controlled without the use of herbicides. Research as to the most effective treatment is widespread and ongoing. It is also important to have a plan to re-vegetate the site with desirable trees and shrubs, once the Tree-of-heaven is knocked back.
For information on how to identify and control Tree-of-heaven or how to better manage your trees, contact the Ohio Department of Natural Resources Division of Forestry at 614-265-6366.