Suppression

Stinktree

Category: Medicines - plant based

Type

Voluntary

Introduction and description

 

Ailanthus altissima  commonly known as tree of heaven, ailanthus, stinktree or in Standard Chinese as chouchun (Chinese: 臭椿; pinyin: chòuchūn; literally: "foul smelling tree"), is a deciduous tree in the Simaroubaceae family. The name ailanthus is derived from the Ambonese word ailanto, meaning "heaven-tree" or "tree reaching for the sky".

The current name in Chinese, chouchun is a relatively new appellation. People living near the lower Yellow River know it by the name chunshu (simplified Chinese: 椿树; traditional Chinese: 椿樹; pinyin: chūnshù), meaning "spring tree". The name stems from the fact that A. altissima is one of the last trees to come out of dormancy, and as such its leaves coming out would indicate that winter was truly over.

As can be seen from its name, the one distinctive feature of this tree is its smell.  All parts of the plant have a ‘distinguishing strong odour that is often likened to peanuts, cashews, or rotting cashews.’  A. altissima is dioecious, with male and female flowers being borne on different individuals. Male trees produce three to four times as many flowers as the females, making the male flowers more conspicuous. It is the male plants that emit the odour while flowering to attract pollinating insects.

Apart from its medicinal uses, the tree has been grown extensively both in China and abroad as a host plant for the ailanthus silkmoth, a moth involved in silk production. Samia Cynthia produces silk that is stronger and cheaper than mulberry silk, “although with inferior gloss and texture and it is unable to take dye”. This type of silk is known under various names: "pongee", "eri silk" and "Shantung silk", the last name being derived from Shandong Province in China where this silk is often produced. Its production is particularly well known in the Yantai region of that province.

It is also considered a good source of firewood across much of its range as it moderately hard and heavy, so is used to make charcoal for cooking.

Description

A. altissima is a medium-sized tree that reaches heights between 17 and 27 metres (56 and 90 ft) with a diameter at breast height of about 1 metre (40 in).  It is a very rapidly growing tree.  Growth of one to two metres (3.3 to 6.6 ft) per year for the first four years is considered normal. Shade considerably hampers growth rates. Older trees, while growing much slower, still do so faster than other trees.

Ailanthus produces an allelopathic chemical called ailanthone, which inhibits the growth of other plants.  The inhibitors are strongest in the bark and roots, but are also present in the leaves, wood and seeds of the plant. It can kill virtually any seedlings.  It is lethal or highly damaging to both hardwoods and conifers, with the white ash (Fraxinus americana) being the only plant not adversely affected. The chemical does not, however, affect the tree of heaven's own seedlings.

Ailanthone, the allelopathic chemical in the tree of heaven, is a known antimalarial agent.

 

A. altissima is short lived and rarely lives more than 50 years, though its remarkable suckering ability makes it possible for this tree to clone itself indefinitely and live considerably longer.

The bark is smooth and light grey, often becoming somewhat rougher with light tan fissures as the tree ages. The twigs are stout, smooth to lightly pubescent, and reddish or chestnut in colour. The branches are light to dark gray in colour, smooth, lustrous, and containing raised lenticels that become fissures with age. The ends of the branches become pendulous.

The buds are finely pubescent, dome shaped, and partially hidden behind the petiole, though they are completely visible in the dormant season at the sinuses of the leaf scars. The leaves are large, odd- or even-pinnately compound, and arranged alternately on the stem. They range in size from 30 to 90 cm (0.98 to 2.95 ft) in length and contain 10–41 leaflets organised in pairs, with the largest leaves found on vigorous young sprouts.

 

The flowers are small and appear in large panicles up to 50 cm (20 in) in length at the end of new shoots. The individual flowers are yellowish green to reddish in colour, each with five petals and sepals. The sepals are cup-shaped, lobed and united while the petals meet at the edges without overlapping, and are white and hairy towards the inside. They appear from mid-April in the south of its range to July in the north.

The seeds borne on the female trees are 5 mm in diameter and each is encapsulated in a samara that is 2.5 cm long (1 in) and 1 cm (0.39 in) broad, appearing July though August, but can persist on the tree until the next spring. The samara is large and twisted at the tips, making it spin as it falls, assisting wind dispersal.  The females can produce huge amounts of seeds, normally around 30,000 per kilogram (14,000/lb) of tree.

Habitat

 

The tree prefers moist and loamy soils, but is adaptable to a very wide range of soil conditions and pH values.

It is drought-hardy, but not tolerant of flooding.

It also does not tolerate deep shade. In China it is often found in limestone-rich areas.

The tree of heaven is found within a wide range of climatic conditions. In its native range it is found at high altitudes in Taiwan as well as lower ones in mainland China.  Prolonged cold and snow cover cause dieback, though the trees re-sprout from the roots

Distribution

Ailanthus altissima  is native to both northeast and central China, as well as Taiwan. Unlike other members of the genus Ailanthus, it is found in temperate climates rather than the tropics.

The tree was first brought from China to Europe in the 1740s and to the United States in 1784. It was one of the first trees brought west during a time when chinoiserie was dominating European arts, and was initially hailed as a beautiful garden specimen. However, enthusiasm soon waned after gardeners became familiar with its suckering habits and its odour. Despite this, it was used extensively as a street tree during much of the 19th century.

It has escaped cultivation in all areas where it was introduced, but most extensively in the United States. It has naturalised across much of Europe, including Germany, Austria, Switzerland, the Czech Republic, the Pannonian region (i.e. southeastern Central Europe around the Danube river basin from Austria, Slovakia and Hungary south to the Balkan ranges) and most countries of the Mediterranean Basin. In Montenegro and Albania A. altissima is widespread in both rural and urban areas.

Ailanthus has also been introduced to Argentina, Australia (where it is a declared weed in New South Wales and Victoria, New Zealand (where it is listed under the National Pest Plant Accord and is classed an "unwanted organism"), the Middle East and in some countries in South Asia such as Pakistan.

All over the world, in other words, it has become an invasive species due to its ability both to colonise disturbed areas quickly and to suppress competition with allelopathic chemicals.  The tree also resprouts vigorously when cut, making its eradication difficult and time consuming.

Medicinal uses

Chinese medicine

In China, the tree of heaven has a long and rich history. It was mentioned in the oldest extant Chinese dictionary and listed in countless Chinese medical texts for its ability to cure ailments ranging from mental illness to baldness.

 

Nearly every part of A. altissima has some application in Chinese traditional medicine. One of the oldest recipes, recorded in a work from 732 AD, is used for treating mental illness. Another source from 684 AD, during the Tang dynasty and recorded in Li Shizhen's Compendium of Materia Medica, states that when used externally they can be effectively used to treat boils, abscesses and itches.

The dried bark, is still an officinal drug and is listed in the modern Chinese materia medica as chun bai pi (Chinese: 椿白皮; pinyin: chūnbáipí), meaning "white bark of spring". Modern works treat it in detail, discussing chemical constituents, how to identify the product and its pharmaceutical uses. It is prepared by felling the tree in fall or spring, stripping the bark and then scraping off the hardest, outermost portion, which is then sun-dried, soaked in water, partially re-dried in a basket and finally cut into strips.

The samaras are also used in modern Chinese medicine under the name feng yan cao (simplified Chinese: 凤眼草; traditional Chinese: 鳳眼草; pinyin: fèngyǎncǎo), meaning "herbal phoenix eye". They have been clinically shown to be able to treat trichomoniasis, a vaginal infection caused by the protozoan Trichomonas vaginalis.

Bioremediation

 

But it also has a more modern application as a bioremedial plant. 

Ailanthus is among the most pollution-tolerant of tree species, it can even withstand sulfur dioxide, which it absorbs in its leaves. It can withstand cement dust and fumes from coal tar operations, as well as resist ozone exposure relatively well. Furthermore, high concentrations of mercury have been found built up in tissues of the plant, meaning it can chelate mercury.  Ailanthus has been used to re-vegetate areas where acid mine drainage has occurred and it has been shown to tolerate pH levels as low as 4.1 (approximately that of tomato juice). It can withstand very low phosphorus levels and high salinity levels. The drought-tolerance of the tree is strong due to its ability to effectively store water in its root system. It is frequently found in areas where few trees can survive.

In northern Europe the tree of heaven was not considered naturalised in cities until after the Second World War, when it colonised areas of rubble of destroyed buildings where most other plants would not grow.

A Tree Grows in Brooklyn -  Betty Smith
There's a tree that grows in Brooklyn. Some people call it the Tree of Heaven. No matter where its seed falls, it makes a tree which struggles to reach the sky. It grows in boarded up lots and out of neglected rubbish heaps. It grows up out of cellar gratings. It is the only tree that grows out of cement. It grows lushly...survives without sun, water, and seemingly earth. It would be considered beautiful except that there are too many of it.

Like bracken it is spreading like wildfire, but we need to pause here.  Nature attempts to heal herself and the spread of all these apparently noxious plants may actually be a symptom of a deep rooted malaise of which we are the cause.  It is spreading because we are polluting.

In colder climates, it appears to go where it is needed most.  For example, one study in Germany found the tree of heaven growing in 92% of densely populated areas of Berlin, 25% of its suburbs and only 3% of areas outside the city altogether.

For most landscaping conditions, it has no value as there are too many trees of superior quality; for impossible conditions this tree has a place; selection could be made for good habit, strong wood and better foliage which would make the tree more satisfactory; I once talked with an architect who tried to buy Ailanthus for use along polluted highways but could not find an adequate supply [...]— Michael A. Dirr, Manual of Woody Landscape Plants

All he needed to do was wait!

Modern research

 

The observations below from Dr Duke and other research provides the detailed description of its uses, however, it is worth pointing out that this tree has anti-fungal, anti-parasitical, antiviral and antibacterial properties.  Since all illness is caused by pathogens such as these or toxins such as heavy metals, radiation and hypoxia, and the Tree of Heaven can also offer help here too, I think we need to realise this is a tree of some importance medicinally.

A very heavenly tree.

Related observations