Love your African proverbs @joanstewart. So many that I have never heard before. And it is news to me that guava trees are not indigenous to South Africa. We have one in our garden...
Living in Johannesburg, I remember one April Fool's joke where they announced in the media that Jacaranda trees are invasive and that they will all be removed. The uproar was huge. They are in full bloom right now and it is a beautiful sight!
Many trees are damaging the ground soil water content, the Jacaranda is listed however I have not heard of them removing the trees, one up the road is in full bloom now as well, very pretty. I think it is up to the person owning the land to make the decision in some cases http://www.invasives.org.za/legislation/item/265-jacarandajacaranda-mimosifolia
So many trees and plants on invasive list it will take years to clear, clearing in nature reserves will most probably start first.
Proverbs are always lessons in living, thanks for visiting and have a great day.