Download Article 53 Revisit Ailanthus Altisiima

Weeds in our Area (Part Fifty Three)
By Bob and Ena McIntyre – Garden Route Branch.
Ailanthus altissima
No doubt after a refreshing and inspiring break flavoured by happy reunions with friends and
family we are all looking forward to an exciting and rewarding 2006.
To keep our newcomers in the picture, we continue our series with revisits of the really persistent
alien invasive flora in our area. Ailanthus altissima, possibly better known by its common name
“tree-of-heaven” - although judging by its rampant spread a more appropriate name would
probably be “tree-of-hell” is yet another that is making itself inordinately at home in Wilderness
village and environs. There is just no good reason to have or cultivate this plant – it is weedy,
poisonous and stinky (see identification below). Back in the early 50’s it’s only recommended uses
were as avenue trees or windbreaks. A native of China, fast growing and becoming very tall, it was
once again a suitable specimen for the impatient gardener. Gardening experts sounded an early
warning that your tree-of-heaven would not make you popular with your neighbours and was only
suitable for the very large garden where it had to be planted well away (20m) from any cultivated
area. There are several mature specimens of Ailanthus altissima and a profusion of young trees
and saplings on the vacant site of the hotel annex north of Heights Road opposite the Chapel, a
large and ever-increasing clump on the south side of Krantz Lane and to our utter dismay they are
also present and rapidly spreading in the “Bird Sanctuary”.
Identification: The mature trees are tall (up to 20m) and spreading (up to 10m) across the crown
and deciduous for a short period. The dark green, yellow
tinged compound leaves and reddish-brown stems of young
plants are disproportionately large (up to 1000mm long) giving
saplings an aggressively robust appearance. The individual
leaflets are characterised by 1-4 basal gland-bearing teeth. The
leaves have a bad smell when crushed. The small greenishyellow flowers appear in Oct – Nov in large terminal sprays and
are followed by striking rust-red seeds. The leaves and flowers
are poisonous and these, as well as the bark are skin irritants.
The flowers have an unpleasant smell.
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 - any
regrowth from suckers or seed germination must be removed
and destroyed. The plants invade forest margins, roadsides and
rivers in 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 arise profusely.
Control: The plant multiplies and spreads in much the same way as Lantana camara and the same
approach is appropriate – on young plants use a foliar spray and on more mature specimens cut
the stems low down and apply herbicide to the cut surfaces. This is a persistent pest so follow-up
is critical. No specific herbicide is currently registered for this particular species.
Indigenous substitutes: Rooi essenhout (Trichelia emetica) is a fast-growing tree with a noninvasive root system as is Wild peach (Kiggelaria africana). Podocarpus falcatus (Outeniqua
Yellowwood) and Podocarpus henckelii (Henckel’s yellowwood) are two more suitable species. All
these provide excellent shade and are firm favourites with our feathered friends.
References: “ALIEN WEEDS AND INVASIVE PLANTS” by Lesley Henderson. Copyright © 2001
Agricultural Research Council. A-Z of Gardening in South Africa by W.G. Sheat. Ornamental Shrubs
and Trees for gardens in Southern Africa by Una van der Spuy