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Botanical Name : Ailanthus altissima Mill.
Species: A. altissima
Synonyms : A. glandulosa
Habitat : It is native to northern and central China, Taiwan and northern Korea. In Taiwan it is present as var. takanai. In China it is native to every province except Gansu, Heilongjiang, Hainan, Jilin, Ningxia, Qinghai, Xinjiang, and Tibet.
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. In the U.S. it is found in arid regions bordering the Great Plains, very wet regions in the southern Appalachians, and cold areas of the lower Rocky Mountains. Prolonged cold and snow cover cause dieback, though the trees re-sprout from the roots.
Ailanthus altissima is a deciduous tree, grows rapidly and is capable of reaching heights of 15 metres (49 ft) in 25 years. However, the species is also short lived and rarely lives more than 50 years.
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). 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. They have lenticels as well as heart-shaped leaf scars (i.e. a scar left on the twig after a leaf falls) with many bundle scars (i.e. small marks where the veins of the leaf once connected to the tree) around the edges. 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 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. All parts of the plant have a distinguishing strong odour that is often likened to rotting peanuts or cashews.
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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 3.0 ft) in length and contain 10–41 leaflets organised in pairs, with the largest leaves found on vigorous young sprouts. The rachis is light to reddish-green with a swollen base. The leaflets are ovate-lanceolate with entire margins, somewhat asymmetric and occasionally not directly opposite to each others. Each leaflet is 5 to 18 cm (2.0 to 7.1 in) long and 2.5 to 5 cm (0.98 to 2.0 in) wide. They have a long tapering end while the bases have two to four teeth, each containing one or more glands at the tip. The leaflets’ upper sides are dark green in colour with light green veins, while the undersides are a more whitish green. The petioles are 5 to 12 mm (0.20 to 0.47 in) long. The lobed bases and glands distinguish it from similar sumac species.
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 are valvate (i.e. they meet at the edges without overlapping), white and hairy towards the inside. They appear from mid-April in the south of its range to July in the north. 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. Furthermore, the male plants emit a foul-smelling odour while flowering to attract pollinating insects. Female flowers contain ten (or rarely five through abortion) sterile stamens (stamenoides) with heart-shaped anthers. The pistil is made up of five free carpels (i.e. they are not fused), each containing a single ovule. Their styles are united and slender with star-shaped stigmas. The male flowers are similar in appearance, but they of course lack a pistil and the stamens do function, each being topped with a globular anther and a glandular green disc. 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 usually persisting on the tree until the next spring. The samara is twisted at the tips, making it spin as it falls and assisting wind dispersal. The females can produce huge amounts of seeds, normally around 30,000 per kilogram (14,000/lb) of tree.
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 purported ability to cure ailments ranging from mental illness to baldness. The roots, leaves and bark are still used today in traditional Chinese medicine, primarily as an astringent. 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. Ailanthus has become a part of western culture as well, with the tree serving as the central metaphor and subject matter of the best-selling American novel A Tree Grows in Brooklyn by Betty Smith.
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 foul smelling odour. Despite this, it was used extensively as a street tree during much of the 19th century. Outside of Europe and the United States, the plant has been spread to many other areas beyond its native range. In a number of these, it has become an invasive species due to its ability to quickly colonise disturbed areas and suppress competition with allelopathic chemicals. It is considered a noxious weed in Australia, the United States, New Zealand and several countries in southern and eastern Europe. The tree also resprouts vigorously when cut, making its eradication difficult and time consuming. In many urban areas, it has acquired the derisive nicknames of “ghetto palm” and “stink tree”.
Tree of heaven is a popular ornamental tree in China and valued for its tolerance of difficult growing conditions. It was once very popular in cultivation in both Europe and North America, but this popularity dropped, especially in the United States, due to the disagreeable odour of its blossoms and the weediness of its habit. The problem of odour was previously avoided by only selling pistillate plants since only males produce the smell, but a higher seed production also results. Michael Dirr, a noted American horticulturalist and professor at the University of Georgia, reported meeting, in 1982, a grower who could not find any buyers. He further writes (his emphasis):
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.
In Europe, however, the tree is still used in the garden to some degree as its habit is generally not as invasive as it is in America. In the United Kingdom it is especially common in London squares, streets, and parks, though it is also frequently found in gardens of southern England and East Anglia. It becomes rare in the north, occurring only infrequently in southern Scotland. It is also rare in Ireland. In Germany the tree is commonly planted in gardens. The tree has furthermore become unpopular in cultivation in the west because it is short-lived and that the trunk soon becomes hollow, making trees more than two feet in diameter unstable in high winds.
A few cultivars exist, but they are not often sold outside of China and probably not at all in North America:
‘Hongye’ – The name is Chinese and means “red leaves”. As the name implies it has attractive vivid red foliage.
‘Metro’ – A male cultivar with a tighter crown than usual and a less weedy habit
‘Erythrocarpa’ – The fruits are a striking red
‘Pendulifolia’ – Leaves are much longer and hang elegantly
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. It involved chopped root material, young boys’ urine and douchi. After sitting for a day the liquid was strained out and given to the patient over the course of several days.
Another source from 684 AD, during the Tang dynasty and recorded in Li Shizhen’s Compendium of Materia Medica, states that when the leaves are taken internally, they make one incoherent and sleepy, while when used externally they can be effectively used to treat boils, abscesses and itches. Yet another recipe recorded by Li uses the leaves to treat baldness. This formula calls for young leaves of ailanthus, catalpa and peach tree to be crushed together and the resulting liquid applied to the scalp to stimulate hair growth.
The dried bark, however, is still an officinal drug and is listed in the modern Chinese materia medica as chun bai pi (Chinese: pinyin: ch?nbáipí), 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 bark is said to have cooling and astringent properties and is primarily used to treat dysentery, intestinal hemorrhage, menorrhagia and spermatorrhea. It is only prescribed in amounts between 4 and 10 grams, so as not to poison the patients. Li’s Compendium has 18 recipes that call for the bark. Asian and European chemists have found some justification for its medical use as it contains a long list of active chemicals that include quassin and saponin, while ailanthone, the allelopathic chemical in the tree of heaven, is a known antimalarial agent. It is available in most shops dealing in Chinese traditional medicine. A tincture of the root-bark has been used successfully in treating cardiac palpitation, asthma and epilepsy.
The samaras are also used in modern Chinese medicine under the name feng yan cao (traditional Chinese: pinyin: fèngy?nc?o), meaning “herbal phoenix eye”. They are used as a hemostatic agent, spermatorrhea and for treating patients with blood in their feces or urine. It was clinically shown to be able to treat trichomoniasis, a vaginal infection caused by the protozoan Trichomonas vaginalis. In occident, an extract of the bark sold under the synonym A. glandulosa is sometimes used as an herbal remedy for various ailments including cancer.
Anecdotal evidence suggests that the plant may be mildly toxic. The noxious odours have been associated with nausea and headaches, as well as with contact dermatitis reported in both humans and sheep, who also developed weakness and paralysis. It contains a quinone irritant, 2,6-dimethoxybenzoquinone, as well as active quassinoids (ailanthone itself being one) which may account for these effects, but they have, however, proved difficult or impossible to reproduce in humans and goats. In one trial a tincture from the blossom and foliage caused nausea, vomiting and muscular relaxation
In addition to its use as an ornamental plant, the tree of heaven is also used for its wood, medicinal properties, and as a host plant to feed silkworms of the moth Samia cynthia, which produces silk that is stronger and cheaper than mulberry silk, although with inferior gloss and texture. It is also 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. The moth has also been introduced in the United States.
The pale yellow, close-grained and satiny wood of ailanthus has been used in cabinet work. It is flexible and well suited to the manufacture of kitchen steamers, which are important in Chinese cuisine for cooking mantou, pastries and rice. Zhejiang Province in eastern China is most famous for producing these steamers. It is also considered a good source of firewood across much of its range as it moderately hard and heavy, yet readily available. There are problems with using the wood as lumber, however. Because the trees exhibit rapid growth for the first few years, the trunk has uneven texture between the inner and outer wood, which can cause the wood to twist or crack during drying. Techniques have been developed for drying the wood so as to prevent this cracking, allowing it to be commercially harvested. Although the live tree tends to have very flexible wood, the wood is quite hard once properly dried.
The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplements, it is always advisable to consult with your own health care provider.