Invasives and Natives: Triffid trials and a soapy native

Dune soap berry (Deinbolia oblongifolia), covered in flowers, attracts a haze of insects.

ENVIRONMENTALLY speaking, one of the saddest sights you can see in South Africa is a huge expanse of what should be natural bush slowly being smothered by that creeping green death we call triffid weed.

Chromolaena odorato, its botanical name, is a member of the daisy family. It was accidently brought from America to South Africa where it has become a problematic alien invasive that is costly us dearly.

According to the Wildife and Environmental Society of South Africa (Wessa) handbook on Invasive Alien Plants in KwaZulu-Natal, a single plant can produce 1,3-milion wind-dispersed seeds so it is not surprising that it spreads virulently when given half a chance.

Another common name for this plant is paraffin bush, not only because its leaves have a distinct paraffin smell. It is also highly flammable even when green and it acts like a wick, leading the flames deep into natural forests that would normally be sheltered from fire.

Once it is well established it is incredibly difficult to destroy even though conservancies and landowners have an arsenal of weapons to fight it, including a number of herbicides and foliar sprays. Even when these are used successfully continuous follow-up action is needed to prevent it from reoccurring. Bio-control agents – that is using carefully checked imported insects that are its natural enemies back in its home – are being used with some success.

If there is some Chromolaena growing in your neighbourhood there is a good chance the wind will blow seeds your way. Before you know it this problematic plant will have settled nicely into a quiet corner of your garden where it will grow and thrive unnoticed if you don’t do regular invasive alien checks.

Look out for its pungent-smelling triangular leaves and its fluffy white flowers.

Chromolaena is a particularly nasty alien invasive so let’s cheer ourselves up by taking a look at a rather delightful and super-useful native plant. The dune soap berry or Deinbolia oblongifolia is one of the characteristic plants you would expect to find in our fast-vanishing dune forests, according to Elsa Pooley’s ‘Trees of Natal’ field guide. Almost every conservationist or horticulturist I have heard giving talks on indigenous gardening, including Elsa, extol its virtues.

From a horticultural point of view, it is a wonderful subject for smaller gardens as it is a dainty tree with an interesting shape. It often plants itself in our coastal gardens where it grows tall and slender without taking up too much room. It has a habit of twisting itself into pleasing sculptured shapes as it grows and has an attractive, not too dense crown of large, dark green compound leaves.

At times it is covered in clusters of cream flowers and a haze of insects seem to surround the little tree then.

However, it is the fruit that really makes it a wildlife winner. I have often heard horticulturist and wildlife friendly gardening proponent Geoff Nichols recommending the dune soap berry and in his book ‘112 Plants for You and Your Bushbuck’, he talks about these berries. About 10mm in diameter, they provide a feast for birds and monkeys during the drier months when food gets scarce. The black-collared barbets that frequent my garden absolutely love them and gobble them down at an amazing rate.

Geoff points out that the leaves are food for the larvae of various butterflies – and some adults like the fermenting fruit. I often see the bright blue and orange peach moth hovering around my dune soap berries so I wasn’t surprised to discover that the tree is host to this species.

This ‘indigenous garden must-have’ has yet another use. As its common name suggests, the seeds lather in water and can be used as soap.


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Judi Davis

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