Tree of heaven

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iAilanthus altissima
Leaves and flowers
Leaves and flowers
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Sapindales
Family: Simaroubaceae
Genus: Ailanthus
Species: A. altissima
Binomial name
Ailanthus altissima
(Mill.) Swingle

Ailanthus altissima (Tree of Heaven or Ailanthus) is a member of the quassia family, Simaroubaceae, native to northeast and central China. It is a deciduous tree, which grows rapidly and can reach up to 25 m tall, rarely 35 m, with a trunk up to 1 m diameter, rarely 1.5 m diameter. The common name is a direct translation of the Indonesian name ailanto for a closely related species in the same genus. Other common names include china sumac, copal tree, stinktree and ghetto palm.

Seeds
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Seeds

The bark of the tree is smooth and light grey, while the stems are reddish or chestnut. Its large, compound leaves are arranged alternately on the stem, and can be 30-60 cm long (occasionally up to 1 m long on vigorous young sprouts) and contain 11-33 leaflets, occasionally up to 41 leaflets. Each leaflet has one to three teeth on each side, close to the base. This helps distinguish it from sumacs (Rhus spp.). Outer parts of the branches droop in a graceful "J" shape.

The flowers are small, yellow-green to reddish, produced in late spring to mid summer in panicles up to 30 cm long. It is dioecious, with trees being either all male or all female. The seed is 5 mm diameter, encapsulated in a samara 4 cm long and 1 cm broad; the samara is twisted, making it spin as it falls, assisting wind dispersal. Female trees can produce more than 300,000 seeds in a year. All parts of the tree produce an unpleasant odour, suggestive of rancid cashews, with male flowers having the strongest smell.

In overall appearance, it is somewhat similar to some species of sumac; Staghorn Sumac Rhus typhina can be distinguished by sumac's red and slightly hairy stems, as well as leaves that are serrated, instead of having the base teeth of A. altissima. Smooth Sumac Rhus glabra, also lacks the base teeth of A. altissima. Ailanthus also grows much taller than all sumac species.

There are two varieties:

[edit] Ecology

Ailanthus is an opportunistic species, thriving in full sun and in disturbed areas. It does, however, exhibit some shade tolerance. It spreads aggressively both by seeds and vegetatively, through root sprouts. It can resprout rapidly after being cut. Ailanthus is among the most tolerant of all tree species to pollution, including sulfur dioxide, and high soil acidity such as that from acid mine drainage (as low as pH 4.1). It has been noted as drought-tolerant, storing water in its root system. It is frequently found along highways and railroad tracks, in abandoned lots in cities, on abandoned mining sites, and in other areas where few trees can survive. Along highways it often forms dense thickets in which few other tree species are present.

Ailanthus produces allelopathic chemicals, which inhibit the growth of other plants. Resistance in various plant species has been shown to increase with exposure; populations without prior exposure to the chemicals are most susceptible to them. A few plants are resistant to these chemicals and form associations with Ailanthus in areas where it is dominant, such as along highways.

People have suggested many factors to Ailanthus' success at naturalising, including the absence of insects eating the plant, lack of exposure of native plants to the Ailanthus' allelopathy, and the widespread human disturbances which favour the tree. Regional variation has begun to show throughout its range, with trees in the colder northern regions producing heavier seeds than those in warmer regions.

[edit] Cultivation and uses

a female tree growing in Chicago, Illinois
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a female tree growing in Chicago, Illinois

Tree of Heaven is a popular ornamental tree in China, valued for its tolerance of difficult growing conditions, and its uses in Chinese traditional medicine. The bark is used to treat dysentery and other bowel ailments. A tincture of the root-bark has been used successfully in cardiac palpitation, asthma and epilepsy. The leaves are also used 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.

There are records of the wood from this tree being used in China. There are problems with using the wood, because the trees exhibit extremely rapid growth for the first few years, the trunk has uneven texture between the inner wood and outer wood, which can cause the wood to twist and/or crack when it is dried after it is cut. Techniques have been developed for drying the wood so as to prevent this cracking, allowing the wood to be commercially harvested. Although the live tree tends to have very flexible wood, the wood is quite hard once properly dried.

It was first introduced to Europe (France and England) by a French Jesuit priest returning from Nanking in 1751, and the United States by William Hamilton, a gardener in Philadelphia in 1784. It soon became a favoured ornamental tree in parks and gardens, and by 1840, it was available in many nurseries. As a second point of entry, the tree was brought to California by Chinese immigrants who worked the gold mines. To this day many abandoned mines have large colonies of it.

Synonyms of A. altissima include A. giraldii and A. glandulosa; under the latter name, an extract of the bark is sometimes touted as an herbal homeopathic remedy for various ailments. However, taken in large doses, the bark extract is highly toxic.

[edit] Control

Tree of Heaven has become a problematic invasive species in many areas with warm temperate climates, including Africa, the Americas, Australia, Europe, and New Zealand. In Europe, it is a problem from Bulgaria west to Portugal and north to Germany, and in the Americas from southern Canada south to Argentina. In the United States it is listed as invasive in 44 states, Washington D.C. and Puerto Rico. [1]

Because of its aggressive spread, vigorous growth, allergenic and allelopathic chemicals, it has become a problem in many areas, out-competing native species. It often grows directly up against a building or structure, where the roots can damage sewers and housing foundations. The trees grow rapidly and produce many offspring in their root vicinity, which also grow rapidly. They also shed many small branches at regular intervals. Digging or breaking the saplings yields an unpleasant smell and a sticky liquid. However, due to their sunlight requirements, their invasive behavior occurs mainly along roadsides and cleared fields, and they are not as successful in invading an already wooded area.

Cutting alone is not sufficient to kill the tree, as it resprouts quickly and abundantly, so eradication programs generally resort to herbicides.

Wikibooks has more information about Ailanthus altissima in A Wikimanual of Gardening.




[edit] Culture & Literature

The book A Tree Grows in Brooklyn by Betty Smith referred to the Tree of Heaven, using it as an analogy for the ability to thrive in a difficult environment. Ailanthus is also sometimes counter-nicknamed "Tree from Hell", from its prolific invasiveness. In cities, it often bears the name "Ghetto Palm", because of its propensity for growing in urban areas, on abandoned or poorly maintained properties.

The Chinese name for this tree contains the descriptive word "stinky".

In some parts of China, unwanted or worthless children may be contemptuously called "ailanthus shoots" [2].

[edit] References and external links

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