Ailanthus altissima

(Mill.) Swingle

Ailanthus

Simaroubaceae

Ailanthus altissima is a deciduous tree species in the family Simaroubaceae. It is native to eastern Asia, but has been cultivated globally and is now a notoriously invasive species. It features as the metaphor of Betty Smith’s novel A Tree Grows in Brooklyn by Betty Smith, alluding to its resilience even in difficult environments (MBG).

Ailanthus altissima f. erythrocarpa

Ailanthus altissima

Ailanthus altissima f. erythrocarpa

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Description

Ailanthus altissima is a medium to large deciduous tree that grows up to 20 m tall, although there are reports of it growing even higher, at 30 m tall. Young trees are often just a single stem. Leaves are alternate and odd-pinnate, 40 to 60 cm long. Leaves have 13 to 27 leaflets that are mostly opposite (except for the terminal one); leaflets are ovate-lanceolate, with the margin being mostly smooth except for some glands at the base. Leaves are dark green above, pale green below, and turning yellow in fall. The bark is gray and relatively smooth, but with short interlacing ridges; twigs are stout, brown with hairs when young. Flowers are borne in large clusters at the ends of branches, and male and female flowers are on separate trees; i.e. they are dioecious. Flowers are light green, tiny, with five petals and either 10 stamens or 5 carpels, produced in late spring to early summer. These mature to become a samara. Samaras are oblong, 3 to 7 cm long and 1 to 1.8 cm wide, twisted, with seeds in the middle of the wing (Sibley 2009; Wu et al. 2008).

Ailanthus altissima can be similar to other trees with alternate, pinnately compound leaves, such as sumacs (Rhus), but those generally have leaflets that are toothed throughout their whole margins; Ailanthus altissima has typically only a few teeth, tipped with glands, at the base. The distinctive fruit is also a helpful identification clue (Sibley 2009).

Three varieties are distinguished, based on the dimensions of the samaras and bark. Variety sutchuenensis has samaras 5 to 7 cm long and 1.4 to 1.8 cm wide, and bark with white lenticels; variety altissima has samaras 3 to 4.5 cm long and 1 to 1.2 cm wide, and slightly grained bark; and variety tanakae has samaras 3 to 4.5 cm long and 0.7 to 0.8 cm wide, and smooth yellow-gray bark. Some sources split Ailanthus vilmoriniana and Ailanthus giraldii as separate species. The former has branches (and sometimes petioles) with soft thorns when young, and the latter has more grayish bark and sinuous-dentate leaflets (i.e. with wavy teeth) (Wu et al. 2008). Other sources do not distinguish these as separate (Hassler 2022); here they are merged with Ailanthus altissima.

Uses

Note: Please see the disclaimer regarding any information about medical or edible uses.

Ailanthus altissima was, and is still, often cultivated as an ornamental or shade tree. Sources disagree whether it was introduced to North America in the late eighteenth or nineteenth century, but in either case it spread across much of the continent, in part due to help from being cultivated (Sibley 2009; Del Tredici 2010). It grows in USDA zones 4 to 8. It grows in a variety of soils, but is extremely tolerant of urban conditions and can grow from cracks in the sidewalk. Nowadays it is seen more as an aggressive weed than an ornamental, as it can spread by producing large amounts of seeds and suckers. Many states in the United States have banned it (MBG).

The dried bark of Ailanthus altissima is commonly used in traditional medicine to treat a variety of ailments, particularly in China, India, and Korea. It is used to stop bleeding, treat asthma and diarrhea, reduce inflammation, and kill parasites (Del Tredici 2010; Li et al. 2021), among other uses, but the scientific evidence for its efficacy is incomplete. It is sometimes used in the papermaking industry (Li et al. 2021). For biological control, Ailanthus altissima may be harvested for pulpwood, firewood, charcoal, and lumber; however, the wood of Ailanthus altissima needs to be prepared first by drying (Asaro et al. 2019).

Distribution

Ailanthus altissima is common in many habitats, particularly the main variety altissima. Variety sutchuenensis is found in valleys and wet forests between altitudes of 1700 and 2500 m, in the southern Chinese provinces of Guangxi, Hubei, Hunan, Jiangxi, Sichuan, and Yunnan. Variety tanakae is a rare endemic found in the alpine forests of northern Taiwan (Wu et al. 2008; Pan 1998). Variety altissima is native to all but a few Chinese provinces, and is naturalized globally (Wu et al. 2008). Some sources also list it as being native to Southeast Asia. It has been introduced to Japan including the Ryukyu Islands; South Korea; Vietnam; Central Asia, South Asia; most of Europe and Macaronesia; Australia; Chile; Argentina; most of the contiguous United States except Montana, Wyoming, North Dakota, and South Dakota; southern Canada; North Africa; and New Zealand (Hassler 2022). It is considered invasive in many places, due to its fast growth, prolific seed production, sprouting back from stumps, and allelopathy (preventing other plants’ growth with chemicals). In addition to being invasive itself, it is also a host of the spotted lanternfly (Lycorma delicatula), another species which is invasive in South Korea, Japan, and North America (Asaro et al. 2019).

Status

While the species as a whole has not been assessed by the IUCN, variety tanakae is listed on the IUCN Red List as “Endangered”. This is because it is restricted to a few populations in the northern part of Taiwan’s mountains, and is threatened by habitat destruction for housing and plantations (Pan 1998).

References

Asaro, C., Becker, C., Creighton, J., and Muncy, J. 2019. Control and Utilization of Tree-of-Heaven: A Guide for Virginia Landowners. Virginia Department of Forestry. [accessed 2022 Aug 21]. <a>https://dof.virginia.gov/wp-content/uploads/Control-and-Utilization-of-Tree-of-Heaven_pub.pdf</a> Del Tredici, P. 2010. Wild Urban Plants of the Northeast: A Field Guide. Ithaca, NY: Cornell University Press. Hassler, M. 2022. World Plants. Synonymic Checklist and Distribution of the World Flora. Version 14.0; last update 2022 August 2. [accessed 2022 Aug 20]. <a>www.worldplants.de</a> Li, X., Li, Y., Ma, S., Zhao, Q., Wu, J., Duan, L., Xie, Y., and Wang, S. 2021. Traditional uses, phytochemistry, and pharmacology of Ailanthus altissima (Mill.) Swingle bark: A comprehensive review. Journal of Ethnopharmacology 275: 114121. MBG (Missouri Botanical Garden), Ailanthus altissima. Plant Finder. [accessed 2022 Aug 20]. <a>https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=287145</a> Pan, F. J. 1998. Ailanthus altissima var. takanai. The IUCN Red List of Threatened Species. <a>https://dx.doi.org/10.2305/IUCN.UK.1998.RLTS.T31349A9628316.en</a>. Sibley, D. A. 2009. The Sibley Guide to Trees. New York: Alfred A. Knopf. Wu, Z. Y., Raven, P. H., and Hong, D. Y., eds. 2008. Flora of China. Vol. 11 (Oxalidaceae through Aceraceae). Beijing: Science Press, and St. Louis: Missouri Botanical Garden Press.

Description

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