In 2017, through our corporate social responsibility scheme, Desert & Delta Safaris has been financially supporting the Peter Smith University of Botswana (PSUB) herbarium. PSUB is making their collection of preserved plants useful and accessible to a wider public, including those who plan for and manage the future of the Okavango delta.
The legacy collection of specimens of the flora of the Okavango delta in northern Botswana housed at PSUB are gradually being prepared for digital scanning so that the digital image can be used to enter data into the BRAHMS database that is specifically designed for herbarium management. PSUB’s work focus this year has been on the personal collection of Mr. Peter Alexander Smith who spent more than thirty years living and working in Ngamiland. His collection of specimens dates back to the early 1970s, having digital images of them will remove the need to handle the actual specimens.
As part of their studies, the team at PSUB write monthly articles on their studies in the Okavango Delta. Last month Mr. Mmusi Mmusi, one of the PSUB Herbarium Assistants sent us his article on the waterlilies of the Okavango Delta. If you are as passionate about plants and nature as we are you will find this fascinating. Happy reading!
This month we look at one of the indigenous waterlilies found in the Okavango delta. Its full scientific name is Nymphaea nouchali Burm. f. var. caerulea (Sav.) Verdc. and belongs to the family Nymphaeaceae. Its common names are, in English blue water lily or blue lotus, sometimes also called frog’s pulpit, in Afrikaans it is knowns as blouwaterlelie or kaaimanblom or paddapreekstoel. In SeYei, a tribe of people native to the Okavango delta region, the fruits are called makungara. In Setswana the plant and its edible rhizome is called tswii.
The waterlilies family, Nymphaeaceae, is an old and evolutionarily primitive one. ‘Numphaios’ is ancient Greek and means sacred to the nymphs. A ‘nymph’, in Greek and Latin mythology, is a minor female nature deity and they were the crafters of nature’s wild beauty. The meaning of the specific epithet ‘nouchali’ has only been traced with the assistance of staff at Kew who reported, to the South African National Biodiversity Institute, that one of their specimens contains a note that Noakhali is a district in Bangladesh. ‘Caerulea’ is from Latin meaning blue and refers to the flower colour. The genus Nymphaea consists of roughly 40 species found in tropical and temperate climates of both hemispheres. The family is full of synonymy, because different populations, or colour forms, have been described as separate species. These have since been sunk (combined back) into one species. In some cases the same plants have been described as different species by different botanists, or the name of one species has been misapplied to another species. It all gets rather confusing!
Commercially, there are many variants and hundreds of hybrids available, they come in all colours, shapes and sizes. This beautiful plant commonly seen on the slower flowing rivers of the Okavango delta and in the floodplains, is a rooted, perennial aquatic herb with a spongy tuberous rhizome anchored in the soil by spreading roots. The water lily does not have a true stem, the leaves are on long petioles (leaf stalks) that arise directly from the rhizome.
The leaves are large and flat, rounded or oval sometimes with notched margins, floating on water surfaces, up to 40 cm in diameter. The leaves are cleft, almost to the centre, where the petiole is attached. This cleft allows the leaf flexibility, allowing it to move with waves or under pressure from a bird’s foot and not be submerged or broken. The leaves are relatively short-lived and are replaced regularly throughout the growing season. They start out as a soft shiny green at the centre of the plant. As they age, the petiole lengthens, pushing the leaf towards the outer perimeter making room for the new growth, the leaves may develop light brown or purple splashes. One plant can spread over an area of about 1 metre.
The large flowers are blueish-white, fading to white as they mature. They are held above the water at the tip of the petiole and appear almost constantly from spring until the end of summer (September to February). They are bisexual, star-like and regular (actinomorphic), with 4 sepals, green on the outside and white to blue on the inside, and many blue petals. In the centre of the flower are numerous bright golden yellow stamens. The flowers open in early to mid-morning and close completely in late afternoon and stay closed all night. The opening and closing mechanism of the flowers is controlled by the sepals. If they are removed, the flower loses the ability to close. A fully open flower lasts for about four days. The flowers are sweetly fragrant and are visited constantly by bees who are the most likely pollinator.
The tubers, known as ‘tswii’, form part of the diet of the local people, they may be eaten raw or are more commonly boiled with either fish or beef. The tubers can be used for dyeing of palm leaves which are used to make baskets. The baskets from the Okavango delta region are valued craft items known globally for their complex beauty. The roots and stem are used as a diuretic, decoction of the flower is said to be narcotic and an aphrodisiac, the leaf is applied directly to the affected area to treat blisters. Pigmy geese, wattled cranes and some fish species feed on the tiny seeds inside the fruit. Honey bees and other insects utilize the nectar produced by the flower. The ripe fruit consists of many greyish-black seeds, these have been eaten by man and can be ground in to flour.
This article was written by Mr. Mmusi Mmusi PSUB Herbarium Assistant and edited by Mrs. Frances Murray-Hudson, PSUB Data Mobilzation Project Assistant PSUB Herbarium at the Okavango Research Institute, University of Botswana, Maun. The image of specimen is © PSUB 2017 and the photographs ©Mmusi Mmusi 2017
For more information on the Peter Smith University of Botswana Herbarium (PSUB) visit http://www.orc.ub.bw/index.php/psub.