Flamingo - Nature - The extraordinary sausage tree
Text by Abigail Amos
Although the baobab richly deserves its place as a symbol of sub-Saharan Africa, the extraordinary sausage tree is equally interesting and much valued by people who know it well. It is common in tropical areas where intermittent good rains occur, but also thrives in the arid years, occurring as far north as Senegal and Sudan, and as far south as the Transvaal Lowveld in South Africa.
Sometimes referred to as the German sausage tree, presumably because it is the Germans who are associated with the production of outsize sausage delicacies, its scientific name is Kigelia africana, and it belongs to the family Bignoniaceae. Spread over such a large geographical area, it is recognised for its species niche successes and has many localised names. In Caprivi, where the flowers yield a pinkish dye and the fruit a red-brown, it is referred to as mopolota and kazungula. Its Afrikaans name is, of course, worsboom. Sometimes reaching over 20 metres in height and rounded in shape, it isn’t amongst Africa’s tallest trees, but is distinctive. It has a tendency to aloofness, single trees preferring a little space, socialising at a distance with other kinds rather than occurring in their own family groups.
The glossy rounded leaves are paired on elegant stems. They are an important source of livestock nutrition during the dry season. The sensational, vulgar flowers flaunt themselves, grouped together invitingly on their pendulous stems. To maximise pollination opportunities and minimise the threat from downpours, only one or two flowers on each stem open on successive nights. They are crumpled and convoluted like a voluptuous unmade bed. With a deep throat and wide gape, they are usually red to maroon purple, sometimes more pink, the stamens lurking beneath the upper lobes, the outer surface of the petals pale and reptilian. The fruits are often a metre in length, smooth-skinned in their youth, coarse with old age. Maturing from pale grey-green to woody, fibrous brown, they dangle heavily beneath the branches on long stalks, then lie undisturbed for years on the bare ground underneath the tree, generating their own micro-ecology. Successful years produce fruit, each weighing as much as ten kilograms.
The best way to experience a day, or preferably a night, in the life of the sausage tree is to camp close beside it. Choose a site west of the trunk with the tent opening facing the tree, so that you have a full view of both evening and early-morning activity whilst enjoying- shade at breakfast time. In order to cause minimal upset to the abundant wildlife whose world thrives beneath the tree, clear only the necessary area of decaying sausage fruits and desiccated flowers. With sundown, the flowers begin to open and a vague musky scent can be detected. The big hawk moths arrive. Their interest seems exploratory rather than nutritional. Perhaps the flowers are too deep for them to venture into, or perhaps the taste of the nectar offered by the flowers does not meet their expectations. The first few hours after darkness bring the bats, the industrious pollinators. The musky perfume becomes dense and powerful and attracts them in large numbers. Their activity in the tree can be heard on still nights as they gorge themselves on nectar. They seem undisturbed by concentrated torchlight. Bats frequently eject sticky urine, so keep drinks and food covered. Some potential for successful pollination by flying feeders may remain until just before sunrise, when the sunbirds come to enjoy the feast, but by that time the flower trumpets are falling to the ground.
Elephants and monkeys browse on the sausage-like fruits, but otherwise they are largely ignored unless food is scarce. Authoritative sources tell us that they can be poisonous to man, especially when green, but their many vernacular applications include ingestion to combat a diversity of problems. Traditional authorities have long used the fruit pulp beneficially in the treatment of skin ailments, and the validity of the active properties is now proved by research and recognised in commercial marketing. The fermentation of the village brew is enhanced by the addition of cooked slices of the sausage tree fruit. A traditional and apparently effective use is to add slices to the drinking water of the cattle to protect them against parasitic worms and leeches. Local women say that there was a time when wives would grate a little of the fruit and add it to their husband’s relish as an aphrodisiac, but they perceive this practice as symbolic rather than medicinal and will not vouch for any benefits. They insist, giggling, that the ploy is no longer practised.
In their book Peoples’ Plants Gericke and van Wyk tell the story of the sausage tree seeds taken back to America’s Californian coastline, where they happily germinated and flourished. No one could understand why, despite their thickly perfumed attraction, they refused to reproduce themselves, and why it was that their seeds would not grow. Coincidentally, and many years later, ladybirds were introduced to the orange groves of California in an effort to curb scale insects that were making serious inroads into citrus crops. Ladybirds are voracious predators on scale insects and made a wonderful job of their task, doing so well for themselves that they soon became unwelcome invaders. It became necessary to find an effective natural predator of the natural predator.
Research eventually determined that the African bat would fit the bill nicely and the bats were shipped across to eat the ladybirds. The bats, in turn, thrived and multiplied.
Around this time, incidentally and independently, an arboreal enthusiast in the vicinity tried again, with little optimism, to propagate the seeds from Californian-grown sausage trees. They germinated abundantly. The parent trees were carefully monitored. As expected, many insects and birds visited them, attracted by the lingering perfume during daylight hours, but the flowers were wilted and dropping and pollination seemed unlikely. By watching at night, however, the answer quickly became obvious; the flowers were gorgeous, the immigrant African bats arrived in large numbers to swill down their ladybird diet with nectar, and it was their furry activity that ensured the successful pollination of the sausage trees.