Tree of heaven, (TOH) (Ailanthus altissima), is an invasive deciduous tree native to China and Taiwan. It was intentionally introduced to the US as an ornamental shade tree.
Tree of heaven is an invasive tree that is favored by the spotted lanternfly (SLF) as a host plant. SLF is an invasive insect that threatens over 70 plant species including grapevines, apple & orchard trees, hops, maple & nut trees.
The aggressive root system of TOH can damage pavement, sewers, and building foundations. The plant reproduces quickly and secretes a chemical in the soil that inhibits the growth of plants near it.
Tree of heaven is a very high pollen producer and therefore may cause seasonal allergies in some people. Depending on sensitivity, some people may develop skin irritation if they come into contact with the leaves, branches, seeds, and bark of TOH. In some cases, exposure to the sap through broken skin, blisters or cuts can cause inflammation of the heart muscle. Gloves and protective gear should be worn by those who have extensive contact with TOH.
Size: Tree-of-heaven can quickly grow to reach heights of 80 feet and up to 6 feet in diameter.
Leaves are pinnately compound, with 10-40 leaflets per leaf, and have an alternate arrangement. Leaflets have smooth edges and two or more glandular teeth at the base that give off a foul odor.
TOH have a “V” shaped leaf scar and a light brown, corky pith that have a burnt peanut butter odor.
Bark is smooth and brownish-green while young, and eventually turns light brown to gray in color to resemble the skin of a cantaloupe.
Seeds are numerous and only found on female trees. Samaras are winged with a single seed and grow in large clusters that remain attached for some time after the tree has dropped its leaves.
Manual: For small infestations, pull out seedling by hand before the taproot develops and be sure the entire root system is removed.
Cutting: Temporarily reduces female ability to spread seeds and may result in increased growth and tree density from root suckers. Cutting is most effective when integrated with chemical treatments.
Chemical: Apply systemic herbicides when the tree is moving carbohydrate to its roots- in mid to late summer (July to the onset of fall leaf color). Applying herbicides prior to this time only damages aboveground growth rather than killing the root system. Always follow chemical label instructions. Multi-year applications may be required.
Apply foliar sprays to the leaves. To avoid contact with desirable plants, this technique is best applied when trees are short and the poulation is dense.
Basal bark applications are a target-specific form of chemical control best applied on trunks less than 6 inches in basal diameter. Apply a concentrated mixture of the ester formulation of triclopyr in oil to the bark of the trunk, starting from the ground line to a height of 12-18 inches and completely around the stem.
For a highly selective treatment option, cut the stem at a downward angle then apply herbicide concentration directly to the cut. For dense stands follow up foliar treatments with bark or hack-and-squirt application on the remaining larger stems.
Well-established TOH stands require repeated efforts and monitoring as initial treatments often only reduce the root sytems.