October Plant Profile: Tree of Heaven
Scientific name: Ailanthus altissima
Common name: Tree of Heaven, Stinking Sumac, Paradise Tree
Family: Simaroubaceae
Native Range: Taiwan and China, hardy to USDA Zone 4
Habit: Grows between 60-90 feet tall and can grow to around 25 feet in a single year. The bark is smooth and tan to gray in early growth. With age, bark will become rugged with heart-shaped leaf scars. The leaves are pinnately compound and range from 1-3 feet long, with 10 to 41 leaflets with teeth at the base.
Ailanthus altissima, the Tree of Heaven, has a pinnately compound leaf structure with lanceolate or lance-shaped leaflets. It is a medium to large tree and has a habit of spreading far and wide due to its samaras (seeds with wings). This tree also forms dense mats from root runners and – whenever a cut is made – it will sprout with more vigor. “It is the most widespread woody invasive species invading wooded areas in the USA, occurring wherever moisture allows.”[1]
In the Washington Park Arboretum, we’ve seen it starting to emerge in several different places. As many on the East Coast might know, this tree is happy to move in wherever it will fit. This tree was brought into the Western world around 1740 by Father Pierre Nicolas d’Incarville, an amateur botanist from France, who mistakenly believed Ailanthus altissima to be Toxicodendron vernicifluum, the high-value varnish tree. There is also text misidentifying it as Rhus coriaria, “European tanners’ sumach.” English nurseryman Philip Miller of The Chelsea Physic Garden, London’s oldest garden, also showcased the tree as one of “fast-growing shade.”
In 1784, William Hamilton was the United States’ “first proud possessor of this rarity.” At The Woodlands, his estate in Pennsylvania, he notably claimed the United States’ first Ginkgo biloba as well. Ailanthus altissima entered the nursery trade in 1820, heavily promoted by Robert Prince Nursery of Flushing, New York. “In its first half dozen years of life, it outstrips almost any other deciduous tree in vigor and growth; we have measured leading stems that had grown twelve or fifteen feet in a single season.” The nursery also touted the tree as bug-free. We now know that Ailanthus altissima hosts several pests, including the spotted lantern fly and the brown marmorated stink bug. These trees rarely live to 60 years old but can spread 100,000 seeds and form dense thickets. They have the possibility of damaging building foundations and sewer pipes, and can compromise stability in concrete, asphalt, and rock walls.
In New York City, many horse chestnuts (Aesculus hippocastanum), American chestnuts (Castanea dentata), Basswood or American linden (Tilia americana), oaks (Quercus species), and other street trees were replaced by the fast-growing Ailanthus. This caused a bout of xenophobia & botanical racism as many New Yorkers felt plants from other countries were stripping away the native trees. The coinciding A. altissima arrival and the American Chestnut Blight could have helped fuel the Sinophobia that still exists around Ailanthus to this day.
Andrew Jackson Downing was a notable critic of the A. altissima arrival… “While he may understandably have been disappointed by the plant, the racial undertones in his comments are unmistakable, especially in the context of a nation seeing its first influx of Asian immigrants. Downing’s comments thus became a reflection of American society and its growing Sinophobia. Perhaps most fascinating though is how a plant could become a conduit for Downing’s anti-Chinese feelings and a reminder of how aesthetics are shaped by the society they represent.”[2] We hope this overview of Ailanthus altissima has has given you some insight into the ways that xenophobia and other biases can manifest in botany. In King County, Ailanthus altissima is currently classified as a Class C Noxious weed.
Find these look-a-likes in the Washington Park Arboretum and elsewhere: Rhus glabra or Smooth sumac, Juglans nigra (black walnut), Rhus typhina (staghorn sumac), Gymnocladus dioicus (Kentucky coffee tree), Toxicodendron vernicifluum syn. Rhus verniciflua (varnish tree), Aralia elata (Japanese angelica tree), and Decaisnea fargesii (Dead man’s fingers).
Learn more about Tree of Heaven lookalikes here.
Sources:
[1] https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.3889
[2] https://www.nyhistory.org/blogs/splendid-usurper-fickle-story-ailanthus-tree
Urban Forests: A Natural History of Trees and People in the American Cityscape by Jill Jonnes
Report a sighting: https://agr.wa.gov/departments/insects-pests-and-weeds/weeds/tree-of-heaven
Washington State Noxious Weed Control Board: https://www.nwcb.wa.gov/weeds/tree-of-heaven
Map of Reported sightings: https://www.eddmaps.org/county.cfm?sub=3003&country=926&id=53033
Article from the Miller Library: https://depts.washington.edu/hortlib/pal/invasiveness-status-of-the-tree-of-heaven/