Tree of Heaven
Ailanthus altissima
NEMBA: Category 1b
English: Tree of Heaven, Chinese Sumac, Tree of Hell, Stinking Sumac, Varnish Tree, Stink Tree
Afrikaans: Hemelboom
Historical scientific names: Rhus cacodendron, Toxicodendron altissimum, Pongelion altissimum
A rapid-growing deciduous tree originating from China, this Tree of heaven is not very heavenly, especially in urban landscapes. Its root system can push up pavement and sidewalks in its unquenched search for resources. It’s leaves also produces a foul odour, reminiscent of rancid peanut butter.
Have you got a better picture?
If you don't mind us using it, please upload it by clicking the Upload button below (you must be logged in to do this)
Origin:
Native to eastern and central China, where it is found in a variety of habitats, including rocky slopes and disturbed areas.
Distinguishing features:
Large, pinnately compound leaves (many leaflets per stalk) that can be up to 90 cm long.
Leaflets have 1-2 coarse teeth at their base, each with a small gland on the underside.
Distinctive, often unpleasant, "rancid peanut butter" smell when leaves or twigs are crushed.
Smooth, greyish bark with pale, diamond-shaped fissures when young, becoming rougher with age.
Produces abundant clusters of flat, twisted, winged, reddish-brown seeds (samaras).
Overall appearance:
A fast-growing, deciduous tree that can reach significant heights, often forming dense thickets or clonal colonies from its extensive root system. It typically has an open crown and a smooth, grey trunk when young.
Height:
Can rapidly grow to 15 to 25 metres tall, though some specimens can reach up to 30 metres.
Width:
The canopy can spread 8 to 15 metres wide, and its root suckers can extend far beyond the main trunk, creating broad clonal patches.
Leaves:
Very large, pinnately compound leaves, ranging from 30 to 90 centimetres in length, arranged alternately along the stems. Each leaf consists of 11 to 41 oval-to-lance-shaped leaflets. The most distinctive feature of the leaflets is the presence of one or two prominent, coarse teeth at their base, each containing a small gland on the underside. The margins of the leaflets are otherwise entire (smooth). When crushed, the leaves and twigs emit a strong, unpleasant odour, often described as smelling like rancid peanuts, cashews, or cat urine.
Flowers:
Small, inconspicuous, yellowish-green flowers are produced in large, upright clusters (panicles) up to 30 centimetres long at the tips of branches. The tree is dioecious, meaning male (pollen-producing) and female (seed-producing) flowers are found on separate trees. Male flowers produce a particularly strong, unpleasant odour, which helps to attract pollinators.
Flowering season:
In South Africa, flowering occurs from spring to early summer, typically between October and December.
Fruits:
The fruits are distinctive, flat, papery, winged seeds called samaras, each containing a single seed in the centre. They are reddish-brown when mature, about 3 to 4 centimetres long, and are produced in huge, hanging clusters that can persist on the tree long after the leaves have fallen.
Seeds:
Each samara contains one small, oval, flat seed. These seeds are highly viable and are efficiently dispersed by wind, allowing the tree to spread rapidly over long distances.
Bark:
When young, the bark is smooth and grey-brown with distinctive pale, often diamond-shaped, fissured patterns that resemble the rind of a cantaloupe or melon. As the tree matures, the bark becomes darker and more furrowed.
Thorns:
None.
Wood:
The wood of Ailanthus altissima is relatively soft, lightweight, and pale, ranging from creamy-white to yellowish. It is not highly valued for commercial timber due to its softness and tendency to rot quickly.
Roots:
Develops an extensive and aggressive root system that spreads widely, often close to the soil surface. These roots readily produce suckers (new shoots), allowing the tree to form dense, clonal colonies, even after the main stem has been cut down. This root system can cause damage to pavements, foundations, and underground pipes.
Soil type:
Remarkably adaptable to a wide range of soil conditions, including poor, degraded, compacted, infertile, acidic, or alkaline soils. It is also highly tolerant of urban pollution and drought once established.
Aspect:
Prefers full sun for optimal growth but can tolerate partial shade. It thrives in disturbed areas, waste ground, and urban environments.
Ediblity:
The tree is not considered edible. While some traditional medicinal uses for its bark and leaves exist in its native range, it contains compounds that can be toxic. The pollen can also be a significant allergen for many people.
Toxicity:
The sap contains chemicals that can cause skin irritation or allergic reactions in some individuals. The pollen is a known allergen. The plant also produces allelopathic chemicals (ailanthone) in its roots, bark, and leaves that inhibit the growth of many other plants around it, giving it a competitive advantage.
Uses:
Historically, Ailanthus altissima was introduced to many parts of the world, including South Africa, as an ornamental street tree due to its rapid growth, tolerance of pollution, and ability to thrive in harsh urban conditions. It was also planted for erosion control and, to a lesser extent, for its low-quality timber. In China, its leaves have been used as a food source for silkworms (though not the common mulberry silkworm).
Ecology:
As an alien invasive plant in South Africa, Ailanthus altissima is highly problematic. Its rapid growth rate, prolific production of wind-dispersed seeds, and vigorous suckering from its roots allow it to form dense, monocultural stands very quickly. These thickets outcompete and displace indigenous vegetation, reducing biodiversity and altering natural ecosystems. The allelopathic chemicals it releases further suppress the growth of native plants. It provides limited ecological benefits to native birds, insects, or mammals compared to indigenous trees.
Distribution and habitat:
Widespread across all provinces of South Africa, it is a common invader in urban and suburban areas, roadsides, railway lines, abandoned farmlands, mining dumps, and disturbed natural vegetation. It is particularly prevalent in the Eastern Cape, thriving in warm temperate to subtropical climates.
Derivation of name:
The genus name Ailanthus comes from "ailanto," a Moluccan word meaning "tree of heaven" or "tree reaching for the sky," referring to its remarkably fast and tall growth.
The species epithet altissima is Latin for "tallest," further emphasising its height.
Historical aspects:
Introduced to Europe from China in 1740 and to North America in 1784, it was initially praised for its hardiness and fast growth, making it a popular choice for urban planting. Its invasive tendencies were not fully understood until much later, leading to its widespread establishment as a serious environmental weed in many parts of the world, including South Africa, where it was introduced for similar reasons.
Interesting facts:
This tree is often called the "Smelly Tree" because its crushed leaves and male flowers can give off a weird smell, a bit like burnt peanut butter or cat wee! Definitely not a perfume you'd want.
Talk about growing fast! This tree is like a rocket, shooting up several metres in just a few years. It's one of the speediest growers around.
It's a real super-parent: each female tree can produce hundreds of thousands of winged seeds that spin like tiny helicopters in the wind, flying off to start new trees far away.
Not only does it spread by seeds, but its roots are like underground ninjas, sending up new shoots everywhere. This means if you cut down one tree, you might end up with ten more popping up nearby!
Friendly alternatives:
Cape Laburnum
Calpurnia aurea
Plant type:
Deciduous or tree
Plant family:
Simaroubaceae (Carib plant name) - Order: Sapindales