Ailanthus Altissima (Tree of Heaven. Hemelboom)

Weeds in our Area(Part One Hundred and Eighteen)

By Bob and Ena McIntyre– Garden Route

Ailanthus altissima (Tree of Heaven. Hemelboom)

Reading about the untold problems experienced with A. altissima in New York and elsewhere in the USA reminded us that this plant is insidiously gaining ground in our area. We decided to revisit the species and to share more fascinating facts. Native to China and Taiwan A.altissima was introduced into Europe in the 1740’s and reached the United States by 1784.Itwas possibly brought to South Africa during the 1800’s. Introduced to various countries all over the world it became a problem in many.

An extract from the book,‘A Tree Grows in Brooklyn’‘ by Betty Smith, says it all “There's a tree that grows in Brooklyn. Some people call it the Tree of Heaven. No matter where its seed falls, it makes a tree which struggles to reach the sky. It grows in boarded up lots and out of neglected rubbish heaps. It grows up out of cellar gratings. It is the only tree that grows out of cement. It grows lushly...survives without sun, water, and seemingly earth. It would be considered beautiful except that there are too many of it.”

However, in the right environment the tree has a variety of practical uses,many of which arelisted in Chinese medical texts for its purported ability to cure ailments ranging from mental illness to balding. The roots, leaves and bark are still used today in traditional Chinese medicine, primarily as an astringent.The tree is grown extensively both in China and abroad as host plant for the ailanthus silk-moth, a moth involved in silk production.

Back in the early 1950’s A.altissima’s only recommended uses as garden plants in our country were as avenue trees or windbreaks. Gardening experts thenalso warned that your Treeof Heaven would not make you popular with your neighbours and was only suitable for the very large garden and planted well away (20m) from any cultivated area. Locally many mature A.altissima and a profusion of saplings can be seenon the vacant site north of Heights Road opposite the Chapel.Anotherever-increasing clump thrives south of Krantz Lane and sadly they are also rapidly spreading in the “Bird Sanctuary”.

Identification: Mature trees are tall (up to 20m) and spreading (up to 10m). Deciduous for a short period, the dark green, yellow-tinged compound leaves and reddish-brown stems of young plants are disproportionately large (up to 1m). The individual leaflets are characterised by 1-4 basal gland-bearing teeth. The male flowers and crushed leaves have an unpleasant smell. The small greenish-yellow flowers appear Oct – Nov in large terminal sprays, followed by striking rust-red seeds. The leaves and flowers are poisonous and these and the bark are skin irritants.

Invasive Status:Ailanthus altissima are Category Three invaders – no trade is permitted and only mature (i.e. mature prior to March 2001) specimens may be retained - re-growth from suckers or seed germination must be removed and destroyed. The plants invade aggressively in mild areas such as ours and will also grow in poor and arid soils. Once established they sucker and spread particularly vigorously as can be seen in the areas mentioned above, to aggravate matters even further - wherever the spreading roots are cut, suckers sprout profusely.

Control: Ailanthus altissima has a similar growth habit toLantana camara and the same approach is appropriate – a foliar spray on young plants and on more mature specimens, very low stem cutsimmediately followed by herbicide application to the cut surfaces. Follow-up is critical. No specific herbicide is currently registered for this species in South Africa.In the United States both the non-selective Glyphosate and selective Triclopyr herbicides are used successfully. Both are systemic herbicides thataffect the whole plant.

Indigenous substitutes: Rooi essenhout (Trichelia emetica), Wild peach (Kiggelaria africana), Podocarpus falcatus (Outeniqua Yellowwood) and Podocarpus henckelii (Henckel’s yellowwood).