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Tree-of-Heaven

Ailanthus altissima

Summary 5

Ailanthus altissima, commonly known as tree of heaven, Ailanthus, varnish tree, copal tree, stinking sumac, Chinese sumac, paradise tree, or in Chinese as chouchun (Chinese: 臭椿; pinyin: chòuchūn), is a deciduous tree in the family Simaroubaceae. It is native to northeast and central China, and Taiwan. Unlike other members of the genus Ailanthus, it is found in temperate climates rather than the tropics.

The tree grows rapidly and is capable of reaching heights of 15 meters (50 ft) in 25 years. While the species rarely lives more than 50 years, some specimens exceed 100 years of age. Its suckering ability allows this tree to clone itself indefinitely. It is considered a noxious weed and vigorous invasive species, and one of the worst invasive plant species in Europe and North America. In 21st-century North America, the invasiveness of the species has been compounded by its role in the life cycle of the also destructive and invasive spotted lanternfly.

Short Description 6

Grows to be 14 to 18 m (45-60 ft) tall with a widespread crown. Each branch usually holds 1 to 25 large compound pointed-shaped and smooth leaves. In June, large clusters of small yellowish-green flowers. Have very large bud scars in the shape of a v or heart. In the summer, female trees produce single-seeded samaras (winged fruits) that may remain on trees for long periods of time. Individual trees may produce about 325,000 seeds per year!

Source: EwA Invasive Pocket Fieldguide | © Earthwise Aware

Description 7

Ailanthus altissima is a medium-sized tree that reaches heights between 17 and 27 m (60 and 90 ft) with a diameter at breast height of about 1 m (3 ft). 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 color. They have lenticels and 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 color, smooth, lustrous, and contain raised lenticels that become fissures with age. The ends of the branches become pendulous. All parts of the plant have a distinguishing strong odor that is often likened to peanuts, cashews, or rotting cashews.

The leaves are large, odd- or even-pinnately compound on the stem. They range in size from 30 to 90 centimetres (1 to 3 ft) in length and contain 10–41 leaflets organised in pairs, with the largest leaves found on vigorous young sprouts. When they emerge in the spring, the leaves are bronze, then quickly turn from medium to dark green as they grow. 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 other. Each leaflet is 5–18 cm (2–7 in) long and 2.5–5 cm (1–2 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 color with light green veins, while the undersides are a more whitish green. The petioles are 5–12 millimetres (0.2–0.5 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 color, 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 odor while flowering to attract pollinating insects. Female flowers contain 10 (or rarely five through abortion) sterile stamens (stamenoids) 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 stigmata. The male flowers are similar in appearance, but they lack a pistil and the stamens do function, each being topped with a globular anther and a glandular green disc. The fruits grow in clusters; similar to the ash tree (Fraxinus excelsior), the fruits ripen to a bright reddish-brown color in September. A fruit cluster may contain hundreds of seeds. The seeds borne on the female trees are 5 mm (0.2 in) in diameter and each is encapsulated in a samara that is 2.5 cm (1 in) long and 1 cm (0.4 in) broad, appearing July through 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, and aiding buoyancy for long-distance dispersal through hydrochory. Primary wind dispersal and secondary water dispersal are usually positively correlated in A. altissima, since most morphological characteristics of samaras affect both dispersal modes in the same way – except for the width of the samaras, which in contrast affects both types of dispersal in opposing ways, allowing differentiation in the dispersal strategies of this tree. The females can produce huge numbers of seeds, normally around 30,000 per kg, and fecundity can be estimated nondestructively through measurements of diameter at chest height.

Invasiveness 5

The earliest introductions of A. altissima to countries outside of its native range were to the southern areas of Korea and to Japan. The tree may be native to these areas, but the tree is generally agreed to be a very early introduction. Within China, it has also been naturalised beyond its native range in areas such as Qinghai, Ningxia, and Xinjiang.

In 1784, not long after Jussieu had sent seeds to England, some were forwarded to the United States by William Hamilton, a gardener in Philadelphia. In both Europe and America, it quickly became a favoured ornamental, especially as a street tree, and by 1840, it was available in most nurseries. The tree was separately brought to California in the 1890s by Chinese immigrants who came during the California Gold Rush. 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 AlbaniaA. altissima is widespread in both rural and urban areas, and while in the first it was introduced as an ornamental plant, it very soon invaded native ecosystems with disastrous results and became an invasive species. 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. In South Africa, it is listed as an invasive species that must be controlled, or removed and destroyed.

In North America, A. altissima is present from Massachusetts in the east, west to southern Ontario, southwest to Iowa, south to Texas, and east to the north of Florida. In the west, it is found from New Mexico west to California and north to Washington. In the east of its range, it grows most extensively in disturbed areas of cities, where it was long ago present as a planted street tree. It also grows along roads and railways. For example, a 2003 study in North Carolina found the tree of heaven was present on 1.7% of all highway and railroad edges in the state, and had been expanding its range at the rate of 4.76% counties per year. Similarly, another study conducted in southwestern Virginia determined that the tree of heaven is thriving along roughly 30% of the state's interstate highway system length or mileage. It sometimes enters undisturbed areas as well, and competes with native plants. In western North America, it is most common in mountainous areas around old dwellings and abandoned mining operations. It is classified as a noxious or invasive plant on National Forest System lands and in many states because its prolific seed production, high germination rate, and capacity to regrow from roots and root fragments enable A. altissima to out-compete native species. For this reason, control measures on public lands and private property are advised where A. altissima has naturalised.

🚧 Control Methods (EwA Content Development in Progress) 6

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Sources and Credits

  1. (c) Claire O'Neill, some rights reserved (CC BY-NC), uploaded by Claire O'Neill, https://www.inaturalist.org/observations/98704224
  2. (c) Jennifer Clifford, some rights reserved (CC BY-NC), uploaded by Jennifer Clifford, https://www.inaturalist.org/observations/108903956
  3. (c) Claire O'Neill, some rights reserved (CC BY-NC), uploaded by Claire O'Neill, https://www.inaturalist.org/observations/116481236
  4. (c) Kate Danziger, some rights reserved (CC BY-NC), uploaded by Kate Danziger, https://www.inaturalist.org/observations/86339949
  5. Adapted by Claire O'Neill from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Ailanthus_altissima
  6. (c) Claire O'Neill, some rights reserved (CC BY-SA)
  7. (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Ailanthus_altissima

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