Pom pom weed / Pom pom-bossie
Flower head in full bloom Pom pom in bloom, Welgevonden
(Images courtesy of Jeremy Goodall and ARC, SAPIA News 2, January 2007)
Description: A perennial, erect (>1m high) herbaceous plant with attractive fluffy pink/purple blooms in summer, (Dec-March); dies back in winter to a root crown. Stem covered with rough hairs, leaves light green.
Origin: South America; introduced to SA as ornamental flower; first recorded as naturalised in the 1960s in the Fountains Valley, Pretoria.
Occurrence: On roadsides, in open grassland, Gauteng highveld (esp. Pretoria), spreading N. into Limpopo (Waterberg, Tzaneen), Mpumalanga (Barberton), Free State and KZN.
Why it is a problem: it is unpalatable to large herbivores and once established in grassland, becomes a serious invader that causes degradation of veld and reduced biodiversity.
It is a declared weed (Category 1): it is prohibited, and must be controlled or eradicated where possible.
Elimination / Control Methods: Problematic because the destruction of above-surface parts by fire or herbicides can stimulate new shots from the rootstock and produce more flowers; but repeated application can be successful.
Physical removal, including the removal of budding flower heads, can control (but not eliminate) the plant; however, because the plant can take two weeks to die, the flower heads should all be picked at the same time, put in a stout plastic bag and burnt. Be careful when picking flowers: the plant produces a great quantity of seed which should not be allowed to be dispersed by the wind. Physical removal is only recommended for isolated plants. Removal of flower heads can help to curb spread but can also stimulate the plants to produce more flower heads.
Herbicides should be applied as early as possible in the growing season, preferably before flowering – but that requires training in identification of the plant. Several herbicides are registered for control of pom pom weed;
- All require the addition of a surfactant (which includes a wetting agent), the name of the preferred one usually being given with the instructions for use;
- All herbicides should be used when freshly mixed (do not leave the solution overnight).
- NB: Follow carefully the instructions provided on herbicide label. Many herbicides can be toxic to other plants and or game and livestock if used inappropriately. (Mis-use of herbicides is also a criminal offence in terms of Act No. 36 of 1947).
Registered Herbicides include:
- Brush-Off (L4535) (metsulfuron methyl 600g/kg): a granular powder. Apply with a back-pack sprayer to foliage of actively-growing plants early in summer.
- Forester (L8891) (formerly called Climax) (metsulfuron methyl 600g/kg ): a wettable powder. Use the surfactant H&R Crop Oil (L6802)). Apply to foliage.
- Plenum 160ME (L7702) (fluoroxypyr/picloram, 80/80 g/L)*: an emulsion.
- Access 240 (L4920) (picloram 240 g/L, a potassium salt)*: a liquid. Use the surfactant Actipron. Apply to foliage from November to January.
*NB: The use of picloram over widespread areas could become problematic, because the agent is very persistent and mobile in the soil as well as being easily absorbed by plant roots. This makes it very difficult to apply in ways that do not risk adversely affecting other vegetation, especially when it is broadcast as a foliant spray rather than on stumps.
Biological control is also under investigation.
Pom pom below Voortrekker monument before (left, Feb 2011)) and after (right, Jan 2012) treatment by Working for Water.
Further annual treatments will be required to eliminate the plant. Images kindly provided by Ferdie Jordaan.
ARC-LNR Weeds & Invasive Plants website: www.agis.agric.za/wip
ARC-LNR SAPIA News 2 (January 2007); 4 (August 2007); 14 (January 2010); 15 (April 2010). ARC – Plant Protection Research Institute, Pretoria. www.arc.agric.za
Bromilow, Clive (2010): Problem Plants and Alien Weeds of South Africa. Briza. Pretoria.
Henderson, Lesley (2001): Alien Weeds & Invasive Plants. Agricultural Research Council (ARC), Pretoria.
Jeremy Goodall, ARC-PPRI, Cedara – pers comm.
Van Zyl, Kathy, (compiler) (2005): Control of Unwanted Plants. Xact Information, Pretoria.
Van Zyl, Kathy, (compiler) (2012): Problem Plant Control Compendium. AVCASA, Midrand
Special thanks to Dr Gerhard Verdoorn of Griffon Poison Information Centre, to Mr Ferdie Jordaan of Arysta Lifescience and to Ms Lesley Henderson of ARC for their invaluable advice and guidance. Their enthusiastic support for this voluntary project is greatly appreciated.