Help map the tree of heaven

The tree of heaven (Ailanthus altissima), is a deciduous tree that originates from the Chinese mainland. Introduced as an ornamental tree, the species has been planted in gardens and on pavements throughout South Africa. It is now spreading uncontrollably to the detriment of biodiversity and infrastructure, and scientists need your help documenting its distribution.

Although a large amount of work has been done on Tree of heaven globally, very little is known of the species in South Africa. The extent of planting, naturalization and invasion is unknown, making the implementation of a suitable management plan a difficult task. Studies have shown that the species exists in all but one of South Africa’s seven biomes (the forest biome being the only exception). Records show that the highest levels of invasion are seen in Gauteng, Free State and the Western Cape. The true extent of tree of heaven invasion in South Africa is however unknown.

Data collection

Gareth Walker from Stellenbosch University is currently documenting the distribution of this invasive tree. Integral to the compilation and implementation of a suitable management plan is establishing the extent of invasion in South Africa. As such all sightings should be reported by logging them on the iSpot web page (www.ispot.co.za) or by sending all sightings to Gareth Walker (This email address is being protected from spambots. You need JavaScript enabled to view it.) at the Centre for Invasion Biology at Stellenbosch University. Sightings should include a picture and the GPS coordinates of the plant – use Google Maps or Google Earth if you don’t have a handheld unit, or set your phone to “geotag” the photo you take. It would also be useful if you are able to include any contact details of the landowner on whose property the plant is found. The intention is to prevent the species from spreading to a point where containment and viable management of the species is no longer an option. This can have dire and irreparable consequences for our natural environment.

Competitive invader

The species is an incredibly hardy and adaptable plant, capable of withstanding adverse weather conditions like drought and flooding, as well as high levels of atmospheric pollution. Vigorous growth coupled with the plants’ ability to produce an allelopathic chemical known as ailanthone may result in drastic alterations to natural habitats. Allelopathic chemicals are effectively herbicides released by some plants which inhibit the growth of (or even kill) neighbouring plants. The release of this chemical can drastically alter your garden landscape turning a beautiful set-up into a rather desolate scene.

No plant, regardless of type, has the ability to withstand the effects of ailanthone. As such, in order to ensure that a beautiful garden landscape is maintained, all Tree of heaven individuals or stands should be removed from your garden immediately. In addition to the natural damage, the tree’s ability to grow and thrive in an urban environment makes the species a threat to infrastructure. Capable of growing through cracks in sidewalks as well as through gutters or even cracks in walls, this plant could ultimately weaken the structural stability and integrity of a building. A case has been reported in which the root system of a Tree of heaven, growing on an adjacent property, has spread far enough to crush the boundary wall and crack the lining of the neighbour’s swimming pool.