Ailanthus altissima: Tree of Heavenly Blessings (or Curses?)

London Fieldworks: Spontaneous City in the Tree of Heaven

In July 2010 an amazing arboreal city for birds and other wildlife materialized in clusters like natural outgrowths around branches and trunks of trees of heaven on two gardens on opposite sides of London. One site was in east London in Islington in the gardens skirting between Duncan Terrace and Colebrook Row. The other site was in the west in Chelsea in Cremorne Gardens. The imaginative constructions expressed the respective biodiversity and ecology of the two sites by reflecting their distinctive architectures. The traditional Georgian townhouse architecture of Duncan Terrace is contrasted at the south end of the gardens with the modern enclave of 1960s social housing flats in Colebrook Row. Adjacent to Cremorne Gardens is The World’s End Estate, designed by British modernist architect Eric Lyons (1912-1980) and associates in 1977, which replaced properties heavily damaged from German bombings during World War II (September 1, 1939-September 2, 1945). A network of elastic bands, developed with the Forestry Commission, attaches the miniature domiciles to the trees and thereby enables them to expand along with their growing host trees for the three years that they are scheduled to remain in situ.

Commissioned by UP Projects as part of their Secret Garden Project, the miniature city was created by internationally known artists Bruce Gilchrist and Jo Joelson, who formed London Fieldworks in 2000 as an umbrella organization to promote creative research on ecological themes through the collaboration of art, science, and technology. The Spontaneous City in the Tree of Heaven aesthetically and powerfully captures the tantalizing range in ecology and biodiversity that is the backdrop in the westernization of the tree of heaven.

Ailanthus altissima is commonly known as tree of heaven, Chinese sumac, or by its generic name, ailanthus. In its native habitat in Taiwan and northeast and central China, its name in Standard Chinese, the official language of the People’s Republic of China, is chouchun (Chinese: 臭椿 chòuchūn ), which means “malodorous tree.” Ailanthus altissima is in the family Simaroubaceae, which oftentimes exhibits bitter bark and fleshy fruits in its genera of pantropical (“across the tropics”) trees.

In Canada and the United States, tree of heaven is an introduced species, meaning that it is living outside of its native habitat and that its insertion into a new habitat was deliberate or accidental. In the case of tree of heaven, it was intentionally transplanted into these two North American countries first as a hardy ornamental and then later as a forestial plant. Brought to his hometown of Philadelphia, Pennsylvania in 1784 by esteemed plant collector William Hamilton (1745-1813), Ailanthus altissima came to the United States by way of England and was extensively planted in urban areas throughout the 1800s. Tree of heaven flourishes in urban, highly industrialized environments. Charles Sprague Sargent (April 24, 1841-March 22, 1927), the first director of Harvard University’s Arnold Arboretum, advocated planting Ailanthus altissima for afforestation:

“. . . for hardiness and rapidity of growth, for the power to adapt to the dirt and smoke, the dust and drought of cities, for the ability to thrive in the poorest soil, for beauty and for usefulness, this tree is one of the most useful which can be grown in this climate. . .” (Garden and Forest 1888: 380).

Tree of heaven’s favorable traits of tolerance to damaged soils and to urban, industrial irritants and pollutants, such as noxious emissions of gas, ensure its prevalent plantings in those areas. Its unfavorable traits of malodor and invasion by root suckering have diminished its incorporation into beautification and green ecology projects.

Tree of heaven is now a naturalized species in these new habitats as it thrives in this new distribution range.

In Canada tree of heaven’s distribution range encompasses the eastern province of Quebec and the east central province of Ontario.

In the United States tree of heaven has firmly established itself in the continental United States (with the exception of Minnesota, Montana, New Hampshire, North Dakota, South Dakota, Vermont, and Wyoming) as well as in Hawaii and in Washington D.C. Tree of heaven is not established in Alaska, nor is it naturalized in Puerto Rico or the U.S. Virgin Islands.

Externals: What Ailanthus altissima looks like

Appearing from mid-April to July, tree of heaven has yellow green flowers in an arrangement of large panicles (Latin: panicula, diminutive of panus “a swelling”) at the ends of new growth. Panicles are compound racemes (Latin: racemes “bunch of grapes” and Greek: rhag-, rhax “grape”). Racemose inflorescence (flower clusters on a shoot) is reminiscent of grape clusters as the flowers develop on pedicles (Latin: pedicellus, diminutive of pes “foot”), short stalks that connect flowers to the main stems, called peduncles (Latin: pedunculus, diminutive of pes “foot”). Flowers open in succession along the growing peduncles as they are borne.

Because female and male flowers are borne on different trees, tree of heaven constitutes a dioecious (Greek: δίς di “double, twice” + οἰκία oikia “house, habitation”) species, with male plants designated as androecious and female plants as gynoecious in order to distinguish individual plant sexuality. The amount of flowers produced by male trees triples or quadruples the amount found on female trees.

Male flowers emit a foul odor that attracts its pollinators.

The tree of heaven produces numerous seeds. As many as 325,000 seeds can be produced by one Ailanthus altissima tree each year. The tree of heaven seed is enclosed within the fruit, which emerges on female trees in late summer to early fall and which, as it is wing-shaped, is termed a samara (Latin: samara “the seed of the elm”). Samaras are yellow to bright red and turn brown at ripening.

Because their wing shape is slightly twisted, samaras twirl like ballerinas as they fall off the tree. The fruit’s wing shape is conducive to wind dispersal and, therefore, contributes to the extensive distribution of Ailanthus altissima, which, as a pioneer species, continuously seeks to expand its territory and is accordingly designed for successful colonization of new habitats, especially uncolonized land which often has poor quality soils.

Renowned American botanist Edgar Anderson (November 9, 1897-June 18, 1969), the third director of the Missouri Botanical Garden (1954-1957), appreciated Ailanthus altissima, unsuccessfully sought to reclaim its position of honor, and poetically rhapsodized about its graceful, wayfaring samaras:

“It blows long distances in a high wind; it whirls gracefully downward in quiet air; it can skid rapidly along over the surface of the snow or along a smooth sidewalk; it also floats effectively in the merest trickle of water. . .” (Edgar Anderson, p. 106)

Another feature that facilitates tree of heaven’s pioneer proclivities is the adventitious growth of buds on surface roots which easily produce shoots that, acting like separate plants, are called suckers. Thus, since it produces suckers, Ailanthus altissima is categorized as a surculose tree (Latin: surculus, diminutive of surus “branch”).

Using a process known as negative allelopathy (Greek: ἀλλήλων allelon “one another, reciprocal” + πάθος pathos “suffering”), tree of heaven produces ailanthone, a toxin that is inimical to the growth of other plant species in their vicinity.

Ailanthus altissima has shallow spreading roots which linger close to or at the soil surface, usually within the upper 18 inches (46 centimeters) of soil. This is another feature which facilitates the expansion of tree of heaven’s territory.

Typical of its family Simaroubaceae, tree of heaven has an alternate leaf arrangement of numerous leaflets along the stem. Leaves are pinnately (Latin: pinna “feather, wing, fin”) compound, meaning that the leaflets are arranged on both sides of the rachis (Greek: ῥάχις rhakhis “spine, ridge”), the main axis or stem. This pinnate arrangement may be odd, i.e., with the main axis terminating in a leaflet, or even, i.e., with the main axis lacking a terminal leaflet. These large leaves, measuring one to four feet (0.3 to 1.2 meters) in length, are composed of smaller leaflets, numbering anywhere from ten to about forty.

The edges (margins) of leaflets are entire (smooth). Along its lower margin, near its base, each leaflet bears two to four glandular teeth. Because their length exceeds their width, with the greatest width near the base, and thereafter tapering to a pointed apex like the head of a lance, the leaves are described as having a shape that is lanceolate (Latin: lanceolatus, from lanceola, diminutive of lancea “a lance”). When the leaves are crushed, they release the same distinctive, unpleasant odor that is emitted by the male flowers.

As a deciduous tree, tree of heaven sheds its leaves seasonally in a process called abscission (Latin: ab “away” + scindere “to cut”).

Ailanthus altissima has smooth, ochre-grey bark that is streaked with vertical lenticels (Latin: lenticella, diminutive of lens “lentil”), which are slits for the purpose of gas exchange between the atmosphere and the tree’s internal tissues.

Twigs are red brown with large heart-shaped leaf scars, which are marks left on twigs by leaves during their autumnal shedding.

Ailanthus altissima grows rapidly at a rate of three to five feet (0.9 to 1.5 meters) annually. Tree of heaven can reach heights of 56 to 90 feet (17 to 27 meters).

With a lifespan of thirty to fifty years, Ailanthus altissima is considered a short-lived species.

Wildlife appeal

Tree of heaven is selectively browsed. Some birds, such as the crossbill (genus Loxia) and the pine grosbeak (Pinicola enucleator), are known to consume its seeds. Deer (family Cervidae) occasionally graze on its foliage.

Insect predation normally does not occur.

Native to China and Japan, the Asiastic garden beetle (Maladera castanea) was first reported in the United States in 1922 in New Jersey. Considered pests in the United States for their voracious nocturnal feedings in which they chew irregular holes in the foliage and blossoms of herbs, fruit plants, ornamentals, and vegetables, they are willing to nibble on tree of heaven foliage.

The larvae of the cynthia moth (Samia cynthia), also called Ailanthus silkmoth, favor Ailanthus altissima as a host plant, but they also infest cherry (genus Prunus subgenus cerasus) and plum (genus Prunus subgenus Prunus) trees.

Another tree of heaven foliage feeder is the Ailanthus webworm (Atteva aurea), a native of southern Florida and, with the exception of Panama, all of Central America.

Cultural and medicinal ethnobotany: Value of Ailanthus altissima to humans

Commercial uses of tree of heaven are primarily explored and valued in China, where the tree is ubiquitous but not invasive.

In the Lower Yellow River Region, from the North China Plain to the delta of Bohai Sea in northeastern China, the common name for tree of heaven is ch’un-shu (“spring tree”). This descriptor was bestowed upon Ailanthus altissima in acknowledgment of its emergence from winter dormancy as a firm indicator of spring’s unequivocal arrival because there it is the last of the area’s deciduous trees to bud. A nursery rhyme of North China praises its vernal (Latin: ver “spring”) clarion call:

“As the unfolding buds of ailanthus appear, the helpless white eyes of the starving people turn clear.” (Dr. Shiu Ying Hu, p. 40)

Silkworms of the cynthia moth (Samia cynthia), which favor tree of heaven as their host plant, produce a silk that is stronger and less expensive than that produced by the better known domesticated silkmoth (Bombyx mori “silkworm of the mulberry tree”) but is considered inferior in gloss and texture.

Cabinetry and kitchen steamers are made from tree of heaven wood, which is pale yellow, close-grained, and satiny.

A proviso is that as Ailanthus altissima ages, its wood becomes brittle and its interior is hollowed. At that point it can still be used as firewood.

The bark, fruit, leaves, and roots of Ailanthus altissima are incorporated into a multiplicity of remedies in traditional Chinese medicine. For example, chun bai pi (Chinese: 椿白皮, chūnbáipí “white bark of spring”), a remedy that is made from the dried bark of Ailanthus altissima, is prescribed by practitioners of traditional Chinese medicine to treat diarrhea or dysentery. Its pharmaceutical name is Cortex ailanthi in traditional Chinese medicine’s Materia Medica. Associated with energy meridians of the large intestine, stomach, and liver, Cortex ailanthi has such medicinal functions as clearing heat, drying dampness, astringing the intestines, stopping bleeding, and killing worms.

Ailanthus altissima in the United States: Whispering tales of its flowery homeland, then smelling “like the plague”

Ailanthus altissima has had a dramatic fall from grace in the three plus centuries of its naturalized existence in the United States. Renowned botanist Edgar Anderson noted:

“It has been more highly praised and more roundly damned than any other tree.” (p. 105)

But Ailanthus altissima found a formidable foe in American landscape designer Andrew Jackson Downing (October 31, 1815-July 28, 1852), often posthumously crowned as the Father of American Landscape Architecture. Downing opposed its presence as a non-native species in the United States, charging it with duplicity and hypocrisy in its juvenile masquerade as a palm tree:

“For a few years, while the tree is growing, it has, to be sure, a fair and specious look. You feel almost. . .that you have got a young palm tree before your door, that can whisper tales to you in the evening of that ‘Flowery Country’ from whence you have borrowed it. . . .A few years pass by; the sapling becomes a tree, its blossoms fill the air with something that looks like curry-powder, and smells like the plague.” (Andrew Jackson Downing, p. 346)

Tree of heaven is now classed in the United States as a non-native, naturalized invasive species. It has this designation because of its previously mentioned physiology which allows it to survive and flourish in damaged areas and to dominate its environment. Apart from its malodor, which is inherent, tree of heaven has never existed as a curse in China, where its beneficial aspects have long been appreciated.

In the late nineteenth century Charles Sprague Sargent argued that the disastrous encounters with tree of heaven in the United States are due to allowing its unfettered growth as an invasive species instead of emphasizing and developing its beneficial aspects. His argument was echoed later in the twentieth century by Edgar Anderson and subsequently by Dr. Shiu Ying Hu (born 1910), esteemed Botanist Emerita of Harvard University’s Arnold Arboretum.

This disinterest in developing tree of heaven’s byproducts is exemplified by research into ailanthus honey near the middle of the twentieth century.

Interestingly, honey from Ailanthus altissima was reported by Ronald Melville (1903-1985), botanist at the Royal Botanic Gardens, Kew, as having an initially disagreeable taste:

“The first impression on tasting it was of a mild floral bouquet, but this was followed by a persistent after-taste reminiscent of cats.”

During the course of gradual tastings the unappealing flavor was discovered to dissipate:

“. . .it was found that the cat-like flavour gradually faded and. . .disappeared entirely, leaving a delicious rich muscatel flavour.” (Ronald Melville, pp. 640-641)

Control

For those holding Ailanthus altissima in disfavor and interested in diminishing or eradicating its strongholds, control is effectuated by a coordinated attack combining manual/mechanical strategies with chemical applications.

Manual and mechanical strategies encompass (1) digging up or pulling young seedlings, especially from moistened soil, (2) cutting back, which is recommended to be commenced in early summer, a time of lowest root reserves, and (3) controlled burning, which often is not an option, especially in an urban environment.

Chemical applications include foliar sprays, basal bark, hack/squirt, and cut stump treatment.

(1) Foliar sprays are effectively applied when tree of heaven is in full leaf, and broad-spectrum herbicides, such as Roundup®, Rodeo®, or Accord®, as well as selective herbicides, such as Triclopyr in, for example, Garlon® 3A and Garlon® 4,are successful eradicators because they are systemic, so they are absorbed by their floral victims and find their way into its root systems.

(2) Basal bark application, involving a solution of oil-soluble Triclopyr product (such as Garlon® 4) or the non-selective herbicide imazapyr in, for example, Chopper®, Stalker®, are most effective in late winter, early spring, and summer.

(3) Most effective in the summer, the hack-and-squirt or injection strategy combines squirting a Triclopyr product (such as Garlon® 3A) into cuts hacked into the tree’s sapwood (younger, outermost layer). Other effective herbicides for this method include Imazapyr (e.g., Arsenal® A.C., Chopper®) and a systemic herbicide cocktail of2,4-Dichlorophenoxyacetic acid (2,4-D) with picloram (e.g., Pathway®). Dicamba (e.g., Banvel®, Vanquish®) is effectively applied in the late autumn.

(4) Best used during the growing season, the cut stump method combines felling the tree with immediate herbicidal application, by painting or spraying, of a dilution of Garlon® 4 or a concentration of Garlon® 3A, and then followup foliar spraying the next year. The herbicides cited for hack-and-squirting are also effective in the stump method.

Ailanthus altissima in the United States: Blessing or curse?

As observed by Edgar Anderson, the coming to America of Ailanthus altissima is a blessing and a curse. In fact, its blessing is its curse. It thrives in urban areas where, for example, it emerges from sewer gratings to provide greenery unexpectedly in the midst of block after city block of brick, concrete, glass, and steel. It also thrives in damaged soils in roadside plantings in rural areas. From these vulnerable bases of operations, Ailanthus altissima sends forth a plethora of seed and sucker explorers to populate successively adjacent habitats so that tree of heaven then emerges in all the best neighborhoods, where its presence is excoriated.

The plucky, persistent ingenuity of Ailanthus altissima --- a trait congruent with the stereotypical American pioneers who steadfastly conquered the vast wildernesses that grew into the United States --- was transmuted into a metaphor for the human struggle against life’s adversities in the 1943 enduringly successful debut novel, A Tree Grows in Brooklyn, by Betty Smith (December 15, 1896-January 17, 1972). As with human life, tree of heaven’s life is innately programmed for glorious heights, for it, too, “struggles to reach the sky.” (Betty Smith, p. 3)

My special thanks to talented photographers who make their fine images available on the internet:

*** London Fieldworks for “Spontaneous City in the Tree of Heaven at Duncan Terrace, Islington” and “Spontaneous City in the Tree of Heaven at Cremorne Gardens, Chelsea”

*** Santa Monica Mountains National Recreation Area for “Male Ailanthus altissima flower” and “Female Ailanthus altissima flower”

*** Chuck Bargeron, University of Georgia, Bugwood.org for “Tree of heaven fruit”

*** Great Smoky Mountains National Park Resource Management Archive, U.S.D.I. National Park Service, Bugwood.org for “Ailanthus altissima leaf arrangement”

*** James H. Miller, U.S.D.A. Forest Service for “Tree of heaven leaf gland in September” and “Tree of heaven Ailanthus altissima foliage”

*** Paul Wray, Iowa State University, Bugwood.org for “Tree of heaven Ailanthus altissima bark”

*** Jan Samanek, Czechia State Phytosanitary Administration, Bugwood.org for “Ailanthus altissima leaf scar and bud,” “Ailanthus altissima flowers,” and “Ailanthus altissima flowers and leaves”

*** Luis Fernández García for August 17, 2004 photograph ‘Ailanthus altissima fruits and leaves, Valladolid, Spain”

*** Shawn Hanrahan for “Samia Cynthia adult male at the Texas A&M Insect Collection in College Station, Texas”

*** John M. Randall, The Nature Conservancy, Bugwood.org for “Ailanthus altissima native at China’s Great Wall”

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Copyright Thursday, May 5, 2011 by Derdriu