PEANUT BUTTER CASSIA

I first became aware of the Peanut Butter Cassia (Senna didymobotrya) while I was living in KwaZulu-Natal. It is a very attractive bush which easily stands out thanks to its erect bright yellow flowers. I first identified it from a delightful book, The Wild Flowers of Southern Africa: Natal. A Rambler’s Pocket Guide by Dr. Winnifred G. Wright, which is filled with detailed black-and-white sketches. I used to colour them in once I had identified a plant and so it is that I see that I first noted the Peanut Butter Cassia in the suburb of Lincoln Meade in Pietermaritzburg in April 1973 and  growing along the beach at Uvongo in October a year later. In July 2019 it was growing prolifically along the Transkei coast.

The scientific name has an interesting origin: Senna stems from the Arabic sana , a name covering species with leaves and pods that have both cathartic and laxative properties. Then comes didymobotrya which is made up of didymo (in pairs) and botrya (cluster). The common name (one among several) of Peanut Butter Cassia relates to the fact that when crushed, the leaves smell akin to peanut butter.

In those days I had no idea that it has been classified as an invader plant, the origins of which lie in tropical East and Central Africa, from the Congo east to Ethiopia and south to Namibia, Zimbabwe and Mozambique. Given its beauty, it was inevitably imported for ornamental use. The trouble is that the leaves are toxic to both humans and livestock. Given its prolific load of seed pods, it is quick to invade roadsides, wastelands, disturbed areas, urban open space, grasslands, savannas, woodlands and riparian vegetation.

Several of these evergreen shrubs are growing in some wasteland next to one of the schools in town. As pretty as they are:

It would make sense for the municipality to remove them, especially as they fall into the Category 1 section of invasive aliens in KwaZulu-Natal, Mpumalanga, Limpopo and the Eastern Cape.

Further useful information can be read at:

http://invasives.org.za/plants/plants-a-z/item/344-peanut-butter-cassia-senna-didymobotrya

http://publish.plantnet-project.org/project/plantinvasivekruger/collection/collection/synthese/details/CASDI

 

TIPUANA TIPU

When we moved into a newly-built house in a recently developed residential area of Pietermaritzburg, it took us a while to clear the builder’s rubble and to level an area for a lawn. As novice gardeners, we turned to the local nurseries for assistance in choosing plants for this garden we were creating from scratch. Given the hot summers we experienced in the then Natal, we naturally wanted to plant some trees for shade.

Having selected a couple of indigenous trees, which we were warned would take a long time to grow, we were encouraged to plant at least one Tipuana tipu tree. This, we were told, was not only fast growing – could reach 4m in its first year – but would provide both shade as well as a pretty show of yellow flowers. This almost sounded too good to be true – of course it was!

We didn’t remain in that house for long enough to see the tree grow to maturity. However, upon moving into our present house in Grahamstown, we discovered an enormous Tipuana tipu tree growing next to the dividing wall on our neighbour’s property. There was an equally enormous one at the far end of our property too – that section has since been sub-divided and belongs to someone else. You can see how it towers over the double storey house (the grey roof of which is on the right) that has since been built next to it.

Because the relatively flat and dusty environment of Mmabatho and Mahikeng in the then Bophuthatswana had few trees, we were delighted at first by the sight of these large mature trees, as well as the Natal fig that has provided us with great bird watching pleasure over the years. At first we didn’t think much of what we innocently regarded as the ‘wear and tear’ of an older tree, for these cracks attracted woodpeckers, nesting barbets and woodhoopes.

We have since discovered some of the many downsides of planting an alien tree such as the Tipuana tipu. It is very fast growing and self-seeds at a speed that keeps us on our toes, whipping out the tiny seedlings as soon as they make their presence known. If you don’t, you will end up with a large tree before you know it. Given that these trees grow to over 20m tall, one has to be careful not to become inundated with them. The green winged seeds dry to yellowish-brown and remain on the tree during winter only to ‘helicopter’ down in the spring breezes. There is no denying that their flowers, which appear from September to January, are pretty – both on the tree and when they cascade to the ground in the wind – but, they not only cover the lawn with a yellow carpet (which I don’t mind) but festoon the swimming pool with a thick yellow carpet of petals.

Despite the longevity of the Tipuana tipu (they can apparently live for several decades), these trees become brittle as they age. Unlike the Natal fig that bends and twists with the wind and then shakes itself back into shape, the Tipuana tipu resists the wind, cracks, and some of the branches twist off, landing with a thud on the ground crushing plants in the process – as we have found to our cost.

The Tipuana tipu originates from South America. While the Tipuana tipu has been planted as street trees in the past, it is an aggressive invader that has now been listed as a Category 3 invader plant and may no longer be planted. They also have aggressive root systems that, in our street, have lifted parts of the tarred road and, in our garden, have made our stone garden path tricky to walk on.