Some trees have surfacing root systems. The most common in the greater Cape Town area are the following. Eugenias (Australian Cherry) Comprosma (Mirror Bush) Monotokas Ficus species Brazilian Peppers These are all fast growing trees that were often planted for screening purposes. The reality is they are very destrucutive. If you have any of these species in your garden you should remove them and replant as there is very little that will be able to compete with their root systems. If you cannot bear to remove the tree, your best bet is to plant Clivias or Asparagus Foxtail ferns. These will manage for a while, but ultimately….the tree shoud go!