Background

Ailanthus, also known as tree-of-heaven and paradisetree, is a major nuisance to foresters, farmers, and homeowners alike. Its prolific seeding and ability to sprout from roots and stumps and grow quite rapidly just about anywhere make it a serious competitor and threat to native species and cultivated crops. On top of that, ailanthus is allelopathic, producing substances that are toxic to and inhibit the growth of neighboring plants.

Leaf

Pith

Identification

Leaves – When present, the leaves are compound and typically measure 1 to 3 feet in total length with 11 to 25 individual leaflets.

Twig – Twig is smooth to fuzzy with large shield-shaped leaf scars after the leaves drop. Ailanthus’s most convincing identification feature is the inside of a broken twig, which smells like rancid or burnt peanut butter and even resembles it in appearance.

Flower – Clusters of yellow-green flowers bloom in late spring to early summer. Male flowers have a disagreeable scent, similar to that of the broken twig.

Fruit – Fruit is a samara, similar to the fruit found on maple trees.

Bark – Bark is smooth and green when young, eventually turning gray and resembling a cantaloupe.

Form – Ailanthus first grows as a single, unbranched stem or multiple stems from the ground, particularly when cut back. An ailanthus mono-cultural thicket will eventually result. Individual stems can grow eight feet in one year and ultimately up to 100 feet in high.

Bark	Leaf scar

Look-alike species

Ailanthus is often confused with native sumacs (Rhus spp.), but can usually be distinguished by sumac’s small, red, fuzzy drupe (fruit) that persists through the winter. Black walnut (Juglans nigra) is also sometimes mistaken for ailanthus when young, due to its compound leaves and large shield-shaped leaf scars. Both of these features are much larger on ailanthus, and the characteristics described above should help make ailanthus less mistakable.

Control

Ailanthus regeneration habits dictate that cutting alone will not kill the tree, but instead promote it to resprout vigorously. Cutting must be combined with chemical control unless excavating the entire root system is feasible, which usually is not. Triclopyr has been verified to provide effective control of ailanthus through basal, foliar, and cut-stump applications. The use of a surfactant for basal and foliar applications is also recommended. For a basal spray application, a 12 percent triclopyr-in-oil solution is recommended. The plant should be sprayed to the point of runoff. For foliar spray, a 2 percent triclopyr in either a water or oil solution is advised. Cut-stump treatments require a 44 percent triclopyr- in-water solution.

The following table displays many general-use chemical formulations labeled for control of ailanthus in forested setting.

References

Jackson, David R. 2005. Herbicides and forest vegetation management: Controlling unwanted trees, brush, and other competing forest vegetation. University Park, Pa.: Penn State College of Agricultural Sciences – Agricultural Research and Cooperative Extension. 31 p.

Miller, James H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. General Technical Report SRS–62. Asheville, N.C.: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p.

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Burch, Patrick L. and S. M. Zedaker. 2003. Removing the invasive tree Ailanthus altissima and restoring natural cover. Journal of Arboriculture 29(1): 18-24.

Disclaimer: Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products which also may be suitable.

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