Ailanthus altissima, or the Tree of Heaven, has a bad reputation. It is often called the ‘Ghetto Palm’ or even the ‘Tree of Hell’ for it’s prolific invasiveness and difficult eradication. Though undesirable to many, this tree has some lesser-known, but remarkable credentials!
A. altissima is native to northeastern China and Taiwan and was accidentally introduced to Europe in 1751. The tree was introduced to the United States in 1784, on purpose this time, to function as a fast-growing ornamental shade tree. By the early 1900’s people’s views of A. altissima shifted and it is now seen as a rampant invader. This tree can grow just about anywhere, and has become naturalized in the United States, seen growing out of any small cracks or crevices in patios and sidewalks, wreaking havoc on building foundations and urban infrastructure. For context, one of these trees survived the Hiroshima A-bomb, only 300 m from where the bomb went off – and is still alive to tell the tale!
This tree is deciduous, fast-growing, and opportunistic. It blooms mid-April to July with clusters of small yellow to red flowers, and male trees emit a foul smell while flowering to attract insects – some have described the smell as similar to ‘rancid cashews’. A. altissima boasts dark green odd- or even-pinnately compound leaves, and can reach heights of almost 30 m tall! This extremophile has been known to grow anywhere and everywhere such as along forest edges, roadsides, in agricultural fields and even reclaimed surface-mined lands, to name a few. A. altissima has even been known to concentrate mercury in it’s tissues and absorb sulfur dioxide in its leaves, making it one of the most pollution-tolerant tree species!
Out of it’s native range A. altissima can take over and displace indigenous plants. It’s seeds can germinate and grow in a wide variety of soils, they have the ability to tolerate high heat, extreme droughts, severe air pollution, and therefore thrive in degraded urban sites where most other species cannot persist. In certain parts of the world A. altissima can grow by as much as 2 m per year, and is thought to be the fastest growing tree in North America! Additionally, it is known to send up suckers from tap roots every 5 – 10 cm, allowing very dense thickets to grow and choke out competing species.
A toxic compound (ailanthone) has been found with A. altissima leaf decomposition. This is called allelopathy, and it inhibits any nearby plants from encroaching on A. altissima. The tree even has a secondary toxin that deters common pests, such as insects and the white-tailed deer from browsing it.
In China, A. altissima was mentioned in the oldest extant dictionary, proving significance almost 2000 years ago. A. altissima has been listed in countless Chinese medical texts for it’s ability to cure everything from baldness to mental illness. The allelopathic chemical, ailanthone, is commonly sold in Chinese medicine shops as an antimalarial agent, and other parts of the plant possess anti-anaphylactic and anti-inflammatory properties. Today, the leaves, roots and bark are all still used in traditional Chinese medicines.
Not only is this tree hugely significant in traditional Chinese medicine, it is important agriculturally and economically in China. A. altissima has been cultivated specifically as a host plant for the ailanthus silkmoth (Samia cynthia). This silkmoth produces silk that is stronger and cheaper than most commonly produced silks.
Lastly, this tree made it’s claim to fame in modern fiction as depicted in Betty Smith’s 1943 book ‘A Tree Grows in Brooklyn’. A. altissima was the central metaphor in the book as it symbolizes the people of Brooklyn fighting for sun and air necessary for their survival in the harsh urban metropolis.
Aside from having important cultural, medicinal and fictional significance, A. altissima has a place in permaculture. In areas where nothing else can grow, brownfields and forgotten places where garbage debris has built up for years and leached toxins into the degraded soil, this tree will thrive.
Cultivating A. altissima for fiber can help to mitigate climate change, reduce pesticide use, remediate heavy-metal laden soils and has the potential to create economic outcomes for people living in invaded ecosystems. Additionally, as they are such fast growing trees, A. altissima can be great for coppicing, the wood burns very well and also makes excellent mulch. If in need of a windbreak, look no further! As it’s so fast growing, a once harsh environment can be made into a nice, sheltered space – prime real estate for less tolerant species.
Moral of the story: don’t judge a tree by it’s invasive tendencies – especially the Tree of Heaven, it’s got some pretty redeeming qualities!
Ailanthus altissima. Retrieved May 23, 2016 from: https://en.wikipedia.org/wiki/Ailanthus_altissima
Conservationists call for ban on ‘Tree of hell’ that threatens to damage native plants. Retrieved May 23, 2017 from: http://www.independent.co.uk/environment/nature/conservationists-call-for-ban-on-tree-of-hell-that-threatens-to-damage-native-plants-9818530.html
Ghetto Conservancy. Retrieved May 25, 2017 from: http://www.oliverk.org/art-projects/proposals/ghetto-conservatory
Invasive Trees in Colorado. Part 1. Retrieved June 1, 2017 from: https://permaculturenews.org/2012/02/16/invasive-trees-in-colorado-part-i/
Tree of Heaven: An Exotic Invasive Plant Fact Sheet. Retrieved May 23, 2017 from: http://www.ecolandscaping.org/05/invasive-plants/tree-of-heaven-an-exotic-invasive-plant-fact-sheet/