Issue 6, August 15, 2023
Tree-of-heaven
Tree-of-heaven (Ailanthus altissima) has gained some attention with the pending threat of invasive Spotted Lanternfly (SLF) making its way to Illinois. Currently, populations have been identified in neighboring states, so it really is just a matter of time before it settles in Illinois. Tree-of-heaven is the preferred host species for SLF. Controlling tree-of-heaven is important in keeping SLF at bay.
Tree-of-heaven plants, Chris Evans, University of Illinois, Bugwood.org
Tree-of-heaven is a rapidly growing deciduous tree reaching up to 70 ft. tall. The leaves, stems, and some flowers emit a strong, unique odor when crushed or broken. Think cat urine or rancid or burnt peanut butter. The leaves are alternate, pinnately compound with 10-40 smaller leaflets, and large (1 to 4 ft. long). Overall, leaf margins are smooth or “entire”. However, leaflets have 1 to 2 rounded teeth near the base. The bark is light grey to brown and resembles cantaloupe skin. It darkens with age. Twigs are greenish brown and contain a spongy, brown pith. The flowers are large, showy, yellowish-green clusters that appear in June. Single-seeded winged fruits (samaras) then develop and may persist on female trees for a long time. Look for the seed located in middle, which can help with proper identification. It is estimated that individual trees may produce 325,000 seeds per year so it can establish quickly, and the spread can be aggressive. It forms dense thickets crowding out native species and is allelopathic, preventing the growth of other plants. It grows best in full sun and is highly adaptable to disturbance. It grows well in poor soils and is often found in urban settings. Tree-of-heaven is commonly confused with black walnut, hickory, and staghorn sumac due to the compound leaves. However, the leaf margins of these species are serrated with teeth and the fruits are different. For more help with identification, check out PennState Extension’s video.
Tree-of-heaven leaves and fruit, Chuck Bargeron, University of Georgia, Bugwood.org
Tree-of-heaven can be difficult to kill. If plants are small, repeated mowing can be used to exhaust the root system. Hand pulling may be possible but wear gloves as extensive contact with sap should be avoided due to possible health concerns. Cutting is not advised for larger plants and hand pulling may not be possible due to clonal growth. Damaging the trunk can stimulate heavy sucker growth which can further increase the size of the infestation. Prescribed fire may be used on seedlings, but this method is not recommended for larger plants because of resultant suckering. For larger plants, the use of glyphosate or triclopyr herbicides is recommended. Plants should be actively growing if a foliar application is to be used. Basal bark applications and cut surface applications can also be effective using triclopyr ester. For more control information, refer to, “Management of Invasive Plants and Pests of Illinois”. Always carefully read and follow all label directions.
For more information about Spotted Lanternfly, check out the Home, Yard, and Garden article, “Be on the Lookout for Spotted Lanternfly”
Author:
Michelle Wiesbrook