 
They can be controlled with Resolva Xtra Tough Weedkiller from Westland or Superfast, Long-lasting, Weedkiller from Neudorff. This should help to eradicate the problem, but several applications may be needed. Most importantly, never let the plants produce seed or the problem will get much worse.
| 
 Gardening Expert:  | 
If you can't find what you are looking for on the website then you can ask one of our experts. To get in touch with us Click Here
We will try to get back to you with an answer as soon as we can.
Did you find this answer useful? Subscribe to our newsletter for gardeing news, projects, special offers and competitions.
Kirstenbosch National Botanical Garden
Cape Town, South Africa
Rio de Janeiro Botanical Gardens
Rio de Janeiro, Brazil
Pukekura Park 
New Plymouth, New Zealand
Vallarta Botanical Garden
Vallarta, Mexico
Humble Administrator's Garden
Suzhou, China
Monet's Garden, Giverny
Giverny, France