|Weeds in our Area (Part One Hundred and Thirty)
By Bob and Ena McIntyre – Garden Route Region.
Melia azedarach (Syringa, Persian lilac, seringboom)
An exceptionally popular and highly recommended gardening subject in days long gone, Melia azedarach’s desirability lead to it gracing just about every garden with enough space anywhere in the country. As ornamentals go it had all those “special” qualities – shade, attractive in flower, very large, quick growing, tolerant of adverse conditions, etc. With such appeal, becoming an aggressive invader where it was happiest, was merely a matter of time. Today it is a particularly serious problem in KZN and in the eastern summer rainfall region of South Africa. It is rated the most invasive tree species in South Africa with over three million hectares of mainly savanna invaded. In Wilderness there are healthy specimens well outside gardens to be found along Waterside Rd and Melkhoutlaan and we have on several occasions weeded out saplings in our own garden – most likely from bird dispersal - therefore certainly worthy of a reminder.
Melia azedarach is native across Asia to Australia. The naturalized version in South Africa is an Indian cultivar. Syringa berries are a very common cause of poisoning in South Africa affecting babies and small children who ingest the seeds. Many cases end up in hospital each year but luckily fatalities are rare. Of interest is that not all trees are toxic and in some instances only trees from particular areas are toxic.
Syringa timber is high quality and drying and maturing of the timber is relatively simple as planks dry without cracking or warping and are resistant to fungal infection. The hard, 5-grooved seeds were widely used for making rosaries and other products requiring beads, before those were substituted by modern materials. The leaves have been used as a natural insecticide to keep stored food insect free – in this instance great care must be taken that the poisonous leaves are not accidentally eaten.
Identification: The adult tree has a rounded crown, and measures between 7 and 12 meters in height. The clusters of small flowers are fragrant, with five pale purple or lilac petals. The fruit is a drupe, marble-sized, light yellow at maturity, remaining on the tree all winter, gradually becoming wrinkled and almost white, at which time the plants look quite tatty. The serrated leaves can be up to 50 cm long, alternate, long-stemmed, 2 or 4 times compound (odd-pinnate); the leaflets are dark green above and lighter green below.
Invasive status: Transformer establishing itself along riverbanks, roadsides, urban open space, wastelands. The plants bear copious numbers of seeds that germinate easily, being spread by birds, water, animals and human activity. Syringa is a declared invader (category three: existing plants at 30 March 2001 may remain - no new plantings i.e. hand-pull emerging seedlings)
Control: Syringa is reported to be very sensitive to ring barking but care must be taken as it coppices readily and follow-up is essential. Herbicides are registered for both basal stem and cut stump applications.
Indigenous Substitutes: The following are suitable indigenous substitutes. Calodendrum capense (Cape chestnut), Dais cotinifolia (pompon tree), Kirkia wilmsii (mountain seringa), Kirkia acuminata (white seringa), Sterculia murex (lowveld chestnut), Heteropyxis natalensis (lavender tree).
References: “ALIEN WEEDS AND INVASIVE PLANTS”: Lesley Henderson. Copyright © 2001 Agricultural Research Council. Problem Plants of SA – Clive Bromilow. Flowering Shrubs and Trees for South African Gardens – Sima Eliovson. Ornamental Trees and Shrubs – Una v.d. Spuy, www.agis.agric.za