Early Detection: Tree-of-Heaven

Author: Elizabeth Spinney, Invasive Plant Coordinator, Vermont Department of Forests, Parks & Recreation, September 2021

In mid-August, a concerned community member brought to the attention of scientists, the presence of an invasive insect. The insect, spotted lanternfly, had never been reported before in Vermont, and was first detected in the United States in 2014 in Pennsylvania, but has spread across the eastern US to 8 states. It hitchhikes on just about anything from wooden pallets, slabs of stone, cars, campers, and even things like backyard grills. What fate awaits it when it travels abroad largely depends on what plant species are available for it to utilize. It can survive on over 70 species of plants, most notable maples, walnuts, oaks, hops, grapes, and apples, often damaging those important crop and hardwood species. However, it appears that a favored plant, invasive Tree-of-Heaven (Ailanthus altissima) may be important in assisting the spread of this insect.

Tree-of-Heaven evolved in China, as did spotted lanternfly. The tree was introduced to the United States in the 1700s as an ornamental plant popular in urban settings (fast-growing, resistant to pollution, provides shade), and was widely planted in the Northeast and California, and has spread to most states.

There are a number of locally evolved trees that look similar to the invasive Tree-of-Heaven: white ash (Fraxinus americana), black ash (Fraxinus nigra), staghorn sumac (Rhus typhina), smooth sumac (Rhus glabra), and butternut (Juglans cinerea). Luckily there are a few ways to distinguish invasive Tree-of-Heaven from its respective local look-alikes:

Leaves

Ailanthus altissima leaflet, showing the glandular teeth and gland at the base. Photo credit: James H. Miller, USDA Forest Service, Bugwood.org

Tree-of-Heaven (invasive) leaves are pinnately compound, alternately arranged, smooth margin with glandular teeth at the base, 1’-2’+ in length, with ~11-41 leaflets per leaf
White ash (local) leaves are pinnately compound, oppositely arranged, mostly smooth or slightly serrated margin, 8-12” in length, with 5-9 leaflets per leaf
Black ash (local) leaves are pinnately compound, oppositely arranged, finely serrated margins, 9-16” in length, with 7-13 leaflets per leaf
Staghorn sumac (local) leaves are compound, alternately arranged, sharply serrated margins, 6-16” in length, with 9-27 leaflets per leaf
Smooth sumac (local) leaves are compound, alternately arranged, serrated margins, 8-18” in length, with 9-23 leaflets per leaf
Butternut (local) leaves are compound, alternately arranged, finely serrated margins, 16-28” in length, with 11-17 leaflets per leaf

Fruit

Tree-of-Heaven (invasive) samaras are oblong, and have a single seed in the center of the papery wing

The winged samaras of Ailanthus altissima oblong, papery, and have a central, single seed. Photo credit: Chuck Bargeron, University of Georgia, Bugwood.org.
White ash (local) samaras are paddle shaped, with thick, wide seeds
Black ash (local) samaras are paddle shaped, and the seeds are thin
Staghorn sumac (local) fruits are small, red and fuzzy and arranged on a panicle
Smooth sumac (local) fruits are small, red and fuzzy and arranged on a panicle
Butternut (local) fruits are green, round - but oblong and pointed, and clustered together

Height

Ailanthus altissima will grow just about anywhere. Photo credit: Ian Trueman, University of Wolverhampton, Bugwood.org

Tree-of-Heaven (invasive) are a large sized tree, ranging from 60-80’ in height
White ash (local) are a large sized tree, averaging 50-80’ in height, but capable of much larger heights
Black ash (local) are a medium sized to large sized tree, averaging 40-70’ in height
Staghorn sumac (local) are a shrub, averaging 15-25’ in height
Smooth sumac (local) are a shrub, ranging from 3-15’+ in height
Butternut (local) are a medium sized tree, averaging 40-60’ in height

Leaf scars

Tree of heaven leaf scar
Ailanthus altissima leaf scar. Photo credit: Jan Samanek, Phytosanitary Administration, Bugwood.org

Tree-of-Heaven (invasive) have large “v” or heart shaped leaf scars
White ash have “c” shaped leaf scars
Black ash have almost “o” shaped leaf scars
Staghorn sumac leaf scars are a strongly curved horseshoe shape
Smooth sumac leaf scars almost encircle the buds
Butternut have a wooly fringe across the top of the leaf scar with no notch, and almost looks like a sheep or goat’s face

Other Characteristics

Ailanthus altissima infestation. Photo credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Tree-of-Heaven (invasive) crushed leaves and male flowers have a skunk-like rotten smell
White ash (local) bark is light gray and uniformly fissured
Black ash (local) bark is gray and scaly or flaky
Staghorn sumac (local) gets its name from the velvety dense hairs that cover much of the plant
Smooth sumac (local) is one of the first plants whose foliage turns color in the fall, going a bright red
Butternut (local) in the Northeast will often exhibit signs of butternut canker

Tree-of-Heaven can establish dense canopies, reducing understory cover diversity, and can be found in forests, forest edges, fields, and human-impacted areas. These trees are short lived, have been documented producing fruit after two years (though not commonly), and can grow 8’ in the first year of growth. Seeds are easily wind dispersed and highly viable, and the tree can reproduce from seed or vegetatively. While shade-intolerant, it has been documented as a pioneer species in forests defoliated or impacted by biotic or abiotic stressors. Where it does grow, the trees release allelopathic chemicals, which reduces competition and will persist in the soil, inhibiting succession. This documented behavior and the continued spread of these trees in Vermont are reasons they are listed as Class B Noxious Weeds in Vermont.

To learn more about invasive Tree-of-Heaven, check out VTinvasives.org and these additional resources: