If you haven’t already done so please pay your subs, $20, which were due on April 1st.



Saturday 1st August : Botanic Garden Walk.  Park at the Herbarium where we will meet Tom at 1045 hours.  Tom is appealing – no pleading for seeds.  He will let us know which special species are required for the garden, but in the meantime any seeds are useful for the exchange system which operates world wide.  Please label your paper packets giving also the date and location of collection.

Sunday 16th August : Choosing a venue for our August outings is always tricky and this year it is even harder because of the drought.  It has been suggested that we should not venture too far, so Lake Chivero (formerly Lake Mac is the obvious choice, where it won’t matter if the bush is leafless – we can view the game.  In any case it will be a pleasure to get out of town and enjoy a day in the sun.  The Girl Guides Association is kindly letting us visit Pax Park, where we will meet at 1000 hours.

Saturday 22nd August : A Walk with Mark in the Cleveland Dam area.  Park in the Main car park where we will meet at 3 pm.

Tuesday 1st  September : Botanic Garden Walk. N.B. Note change to summertime time.

8th to 12th August : We are trying to organize an ‘extra’ trip for this period, perhaps to Burma Valley, and maybe camping. However the water situation might well be the deciding factor. Booking is on a first come basis so please phone Maureen Silva-Jones on 739711 at work or 25837 at home if you’d like to be included.



Sunday 2nd August : To Regina Ruins. A round trip of about 220 kms. Bring tea, lunch and chair.  Rendezvous at Thecla and Roy Mitchell’s house, 5 Glengarry Crescent off the Harare road just beyond Brady Barracks at 8.30 a.m.

Wednesday 19th August : Hillside Dam Walk at 5 pm

Sunday 13th  September : Please note that this is a Second Sunday meeting because we shall be combining with the Aloe and Cactus Society on their usual day for a lecture and slide presentation by the cycad expert Brian Schlacter. The venue is the house of Barbara and Derek Viljoen at 42 Fairbridge Way,  Malindela.

Time 10.30 for 11.00 am.  Please bring chairs, lunch afterwards at Mabukuweni – catering by John Coulson at $38.00 a head. There will be a cash bar. Members who want lunch please phone Clem von Vliet (41619) or Ian McCausland (41945)


On the 9th July we lost a long standing enthusiastic and very knowledgeable member, Dr.J.K.A.Davey – known to us all as Ken.  Ken loved the Zimbabwe bush in all its moods. The Mashonaland Highveld, Matabeleland, Eastern Highlands the Lowveld and especially the Zambezi Valley, were all familiar and home to Ken. He had an encyclopaedic knowledge of their trees, birds and animals which he was always keen to share with his many friends.  Because of this, Pamuzinda Lodge asked him and his wife Lyn to identify and draw up a tree list for the use of visitors to the Lodge.

Once when out ‘birding’ in the Mukuvisi Woodlands in Harare, a member was heard to remark that no one should stop to look at a tree or we would be learning our trees from Ken for the next half hour and forgetting about the birds! We will miss his contagious enthusiasm and love of nature on our future outings, but he will surely be with us in spirit.

To his Wife Lyn and his daughters we offer our sincerest sympathy.




5 people turned up on a grey Saturday afternoon and we drove round to the somewhat dilapidated gate on Blatherwick Road. The purpose of writing up this walk is to mention the rather unusual and unexpected species  (mainly exotics)  which were seen and to report on a subsequent telephone conversation with George Hall which helped to explain the origin of some of these.

Phyllanthus reticulatus. Photo: Bart Wursten. Source: Flora of Zimbabwe

Phyllanthus reticulatus. Photo: Bart Wursten. Source: Flora of Zimbabwe

By the fence is a Dalberga sissoo. This is a native of Asia grown for ornament in this country, but which has been known to become naturalised and is therefore on the National List of trees.  Its leaves resemble Pterocarpus and have broadly ovate, dark green leaflets arranged alternately in a compound leaf. The fruits have a flattened rectangular wing-like structure around the central seed case rather like the other species of Dalbergia we are more familiar with. This tree was planted in the early 1980s.

Nearby, we came across a fine flowering and fruiting specimen of Phyllanthus reticulatus  to our bewilderment at first.  Surely we were at nearly 1500 m in Harare and not by a lowveld river? Later, George enlightened us. The bush was planted there in December 1980. Nevertheless, it has done remarkably well.

After this, we walked down towards the river, examining the more normal tree flora. Even down here we did not escape from exotics. This is a plant of the bamboo family,  Bambusa vulgaris, well-established among the native plants.  As this species rarely flowers around Harare, we assume that it was either planted or had been introduced vegetatively.

I will report at a later stage on the odd-looking Terminalia we found.

All in all, a surprisingly interesting afternoon.

-Mark Hyde



A good number of members gathered in the sunny but chilly Botanic Gardens. Tom’s brief was to concentrate on the succulent Euphorbias and Aloes, but as usual we digressed to look at other interesting species.

To begin with the remarkable genus Euphorbia. According to Mabberley, this is the second largest Angiosperm genus by number of species with 1600. (From the same source, the largest genus is Astragalus with 2000 speoies, only one of which occurs in Zimbabwe). The species Euphorbia vary from tiny prostrate annuals through herbaceous perennials to cactus-like trees.

Euphorbia griseola. Photo: Bart Wursten. Source: Flora of Zimbabwe

Euphorbia griseola. Photo: Bart Wursten. Source: Flora of Zimbabwe

Euphorbia ingens is probably the commonest and most widespread “succulent” Euphorbia occurring at a wide range of altitudes, E.coopeii and E.griseola are also fairly common.

Two endemics of the Great Dyke are growing in the Gardens, E.wildii and E.memoralis,  E.schinzii is another widespread low-growing species, unpleasant if discovered in bare feet.

Turning to the species of Aloe.  om grows the Great Dyke endemic A.ortholopha in a bed to which serpentine rocks have been added.  It is actually advisable to make the soil toxic by adding a magnesium salt.

Aloes easily hybridise with each other, even pairs of species from quite distantly related sections of the genus.  In the same bed was a possible ortholopha x cryptopoda hybrid.

We examined A.cryptopoda.  Its specific name means “hidden feet” and refers to the fact that the inflorescence has prominent bracts which, especially in the immature inflorescence conceal the flower stalks.  Later, we saw A.lutescene, which is similar to cryptopoda.  It grows in the SE of the country and its flowers turn yellow when mature.

On our way from one part of the gardens to another we passed an unusual tree with spherical fruiting heads.  I am ashamed to say it took a lot of prompting from Tom before we recognised its affinity with Breonadia. It was in fact another RUBIACEAE – Burttdavya.

Not far from the Herbarium is a bed of strange-looking plants from the DIDIEREACEAE, all of which are endemic to Madagascar. An especially weird one was Alluaudia procera,  a huge unbranched spiny species with short leaves on the stem.

In passing, we also saw two “stars” of the Zimbabwean plant world-, namely the Lundi Star (Pachypodium saundersii) and the Sabi Star Adenium multiflorum).

Once again, our sincere thanks to Tom for giving his time to guide us through the fascinating Botanic Gardens.

-Mark Hyde



Ken and Betty Blake have resigned from the committee of the Bulawayo Branch. We would like to thank them for all they have done, not only for the Bulawayo Branch but for the whole Tree Society. Considerable help has come from them with our stationery and printing requirements, with organizing field trips and generally keeping in touch.




Boscia matabelensis. Photo: Meg Coates Palgrave. Source: Flora of Zimbabwe

Boscia matabelensis. Photo: Meg Coates Palgrave. Source: Flora of Zimbabwe

Some 28 of us ‘debussed’ close to the south-western boundary on Zebra Loop. Before setting off to look at trees, Val and Wendy produced a specimen picked in the Iland area which they said was Boscia matabelensis (not shown on our tree card) thus providing an exciting find right in town .

Dennis pursued his special interest and produced samples of Acacia ataxacantha, A.gerrardii, A.nilotica, A.rohusta subs. robusta and an unknown which the Herbarium identified as A.hebeclada. We recorded A.rehmanniana and numerous A.nigescens with several of the large old trees bearing huge galls on the larger branches. Many of the trees were completely bare, but Ken managed to find a very impressive Cassia abbreviata pod. Included in our list of species identified were Cassine matabelica and C.transvalensis; Delbergia melanoxylon four Commiphora common to Bulawayo; Kirkia acuminata; Lannea discolour; Pterocarpus angolensis and P.rotundifolius;  Terminalia randii and T.sericea,

Ximenia caffra and X.americana.  A strange looking Schrebera alata eventually proved to be a special find in the form of Vepris zambesiaca.

During the tea break Ken announced that he was giving a month’s notice as Chairman of our branch. I am sure all our members join in thanking him for the hard work that he has done during his term of office. Those of us left on the committee will continue to keep things going until the AGM next year.

After tea we headed for the dry riverbed and across to the rocky outcrops on the east bank of the river where we found Ficus abutilifolia, F.glumosa, F.thonningii,Pouzolzie mixta and Ochna puberula. In all, over 60 specimens were recorded on a well-attended convivial outing in warm sunshine.



For the mid-month tree walk we met at Hillside Dams at 5 o’clock on Wednesday 15th July. Ian had prepared for us three interesting subjects. The first was Ehretia rigida in the BORAGINACEAE family with its characteristic twiggy branchlets.  On studying it in my Palgrave book afterwards I found that it is one of Africa’s good luck charm trees.  Hunters in the Transvaal believe that the strength of their prey will be reduced if a twig is pointed towards it, while a bad-tempered ox is said to become docile if the cattle kraal is made from the branches.  The powdered root mixed with hair from a goat’s head is sprinkled over hunters to bring them luck and a branch is dragged around huts and gardens to protect them from a threatening hailstorm.

Next we looked at Ehretia amoena.  Its leaves were falling and seemed to go a deep purple underneath before drying up altogether and dropping.   We did the tongue test to feel the sandpaper effect and held the leaves against the sunset to see the fine crystalline edging. The wood is evidently quite hard as it is used to make pestles for stamping grain.

Lastly we visited a handsome specimen of a mature Pappea capensis and discussed the leaves which varied a lot.   A few dried up fruits could still be seen and Ian explained the various uses to which they are put such as making soap and lubrication oil.

-C.G. v.V.



With a typical winter morning beginning to thaw out, Maureen suggested that the Nyagui Hills Road would make an interesting deviation prior to our outing at Shamva. As the road began to approach the hills, a halt was called and within a few seconds “treeing” had started.  George appeared with a piece of Cassine matabelica and Maureen pointed out the unusual growing tips on Uapaca nitida.

A slow drive down the road revealed Pericopsis angolensis, Terminalia sericia, whilst the C.molle had already started to change its leaf colour to a dull pink. Some stunted Cussonia arborea and scattered Pterocarpus angolensis and the occasional Kigelia africana gave way to Uapaca and Brachyetegia woodland as the road continued to the summit of the hill.

We reached the summit after a couple of slippery curves only to look out on a superb view of Bindura and Shamva with a bit of luck a Steganotaenea araliacea (Popgun tree) was right next to our stopping place.

Descending again through Brachystegia country the level ground introduced itself with wiffs of Phyllanthus reticulatus and a grove of Acacia polyacantha mixed up with a few A.karoo grew very close to road verge.

Turning off the main road into Shamva, the many indigenous trees planted on the verges were source of much interest. Dombeya burgessiae, still in bloom, followed by Cordia abyssinica enjoying its roadside habitat as did the Albizias namely A.glaberiama and A.chinensis, which was also seen later at the farm house.

By this stage driving and treeing had become erratic so a Lonchocarpus capassa was chosen for a stopping place.  A group of four flourishing Rhus lancea was noticed along with a Bauhinia galpinii and a Rauvolfia caffra.  A sorry looking Kigelia africana allowed Pat, Fiona and Keith and ourselves to meet up and continue to the farm passing an Azanza garckeana, Erythrina abyssinica_and a huge Pileostigma thonniggii on the way through Shamva.

I am looking forward to Dicks article about the farm and would like to thank him and Edone for organising such a superb outing.  Many thanks also to Aubrey and Edone Ann for their hospitality and for showing us the mine workings.




Baboons’ breakfast is Hexalobus monopetalus which belongs to ANNONACEAE, Civet’s breakfast is another story; the civet is omnivorous, nocturnal and has a habit of depositing its droppings in middens to which it returns after wandering far afield to feed. These middens are conspicuous in a clearing or beside a path.

A large sample of droppings collected in May was sundried, washed in several waters, strained through fine netting, washed again and left in the sun to dry.  What a revelation, it took ages to sort it out and even longer to identify.

Contents of a midden in May during a drought :

Animal items were as follows:  black, grey and white feathers, likely to be from Francolin; 105 porcupine quills (longest 5.5cm x 3mm, part of a stouter quill 4.5cm x 4mm) the remainder were immature and sorting them was like the game of “picking up sticks”; ventral scales from a snake; elytra (beetle wing covers); fine hairs 2-3cm in length; numerous ‘insect’ legs; millipede rings very numerous; spider fragments; bone fragment and one long black shiny tapering bristle, its tip was colourless like fishing line, total length 23cm! what was this?

Items of plant origin were as follows : Skeletonized leaves and those of Ziziphus; a wad of green fibrous grass; tufts of very fine grass or Bulbostylus (sedge); many one-seeded fruits of Euclea sp; some similar fruits with remains of a fibrous covering; Parinari curatellifolia fruits in plenty; many star calices and numerous coffee bean like capels from inside the fruit of Diospyros lycioides.  There could have been one mineral item or was it a very hard nut with a fissured surface?  Some dollops were composed entirely of fig seeds, rather appropriate in view of all the ods and ends which are voi ed by the African Civet.

The Bundu Seriés Wild Mammals states that the young of small buck may be taken, there is no mention of the young of porcupine.

The midden month by month could well be a feature of this newsletter, emphasis would be on wild fruits.

It is Protea time.  Today we went for a Protea ride to see how dejected they look when fireguards have burnt them.  P.angolensis had managed to open one bloom before it was flamed.  Protea is one of the easiest genera to recognise.  The hard woody involucral bracts surrounding the inflorescences are distinctive; to the uninitiated the entire inflorescence resembles a single flower with the bracts being petals.  In Protea each floret consists of three fused perianth segments (tepals) and a single free perianth segment.  This can be checked in the field with fresh flowers or remove a few florets from a Protea in a dry arrangement.  The fruit is woody and entirely covered by hairs, a hairy nutlet.  Proteas are distinguished by the size, shape and feel of the leaves, the plant growth habit and marked differences among the inflorescences.  The long lasting dry seed heads on the bushes are called infractescences.  The hairs on the seed when dry raise the seed above sun scorched earth, when moist the hairs gradually close up and let the seed touch the ground to absorb moisture, this happens when a tray of sandy soil is sown with Protea seeds, actually they are one-seeded fruits and the domed dry inflorescence has three kinds of fruit; a few fat ones which contain a seed capable of germination, woody fruit and thin fruit, empty ones may resemble the fertile seeds.  This is one of the Protea’s survival strategies, predators such as rodents have to waste a lot of time looking for the few fruits with seeds in them.  Their seeds are adapted for germination in nitrogen starved soils because the cotyledons (seed leaves) contain a store of nitrogen.  In the wild Proteas are able to thrive in spite of being burnt so long as it happens before the fruits are shed, the term ‘serotiny’ means the storage of seeds on the parent plant until a fire, after which they are released and later geminate where the burn has reduced the plant population so there is less competition.

Another member of the family PROTEACEAE is the genus Faurea, when these bloom look for the floral structure which is arranged differently but is identical, as regards three fused and one separate perianth member, to the Protea species.

You will be lucky to find Protea seeds this season, many seeds are empty, the drought may be the cause of the absence of viable seed, parasitism is rife too.

Lack of information

Identification of wild fruits in civet dung was not as easy as might be expected. It was an exciting challenge and an ongoing one. Reference books describe the fruits but often omit a description of the seed and its method of dispersal. Winter fruits were examined carefully to see if they were the ones in the midden. One revelation concerned [tough dried-out fruit of the tree Azanza garckeana often mulitated for its immature chewy fruits (Chingwa) what was much more interesting was its relationship to cotton Gossypium sp. instead of pure white hairs covering the carpal (seed, there is golden brown ‘teddy-bear fur firmly attached to each seed.

In the barbel incident vlei a lone kudu bull faces us to watch as we rode home after looking at the Proteas.  This was a rare sight on Katawa. A large Egyptian Cobra and a very large Python were seen just as the weather became cold, (9. night temperature of 2 to 4 degrees Celsius on this hill but colder below on level ground), these sightings were reported by an employee.

Trees and History in Ayrshire District

In order that the Ayrshire gold mine be supplied with firewood the B.S..A. Chartered Company reserved l60 sq. miles of heavily wooded country for exclusive use by the mine; and the new railway drew its fuel from this area while carrying wood to the mine. Major C.T.C. Taylor, who owned Nyarapinda Extension (Tinto) many years ago, wrote the history of Lomagundi for “Rhodesiana” No. 10 in 1964.  He quoted from The Rhodesia Herald 11th  Oct. 1904 where it was reported that ‘wood trains run into Ayrshire Camp daily from some 15 miles out and the forest near the line looks like unto him that carrieth a banner when he fainteth‘.  Today the only large trees there are Pericopsis angolensis, they were left as being too hard to cut.  This also happened in the vicinity of the Muriel gold mine.

In 1924 land on Ayrshire farm, owned by Messrs Watkins and Larter, was cleared for tobacco, the task of stumping was made more difficult by the coppice growth in the sandveld woodland.  Along the route to the Mazvikadei dam the absence of venerable old Brachystegia trees is noticeable, a legacy of old time mining.

-Benadicta Graves



During recent visits to locate archaeological sites in the Matopos and northern Mashonaland I began to see a possible correlation between old occupation sites and certain floral types. This is just an‘ intuitive feeling at this stage, but one worthy of pursuit. Such a correlation could certainly prove a useful means of remote sensing, that is the discovery of new sites by both professionals and interested amateurs. The following are just a few ideas and I would appreciate any further observations and suggestions.

Why these correlations occur I think can be divided into two categories. There are those resulting from directly purposeful human activity such as the rooting of “cuttings” (poles in construction), or growing of seeds included in the deposit due to human activity (as food, medicine and spiritual use).  In all these cases it is human activity which has directly led to the concentration of such plants on the site. On the other hand there are floral changes which are indirectly due to human activity.  Here humans have influenced other elements which in turn have influenced the vegetation, eg changing soil conditions, run-off, incidental protection from fire and grazing, etc. It is this reasoning that needs the greatest attention right now.

The most obvious correlation is the dense concentration of thatching grass (Hyparrhenia spp.) on old sites, especially more recent Iron Age sites of the Refuge period. This is not my observation however, rather it was pointed out to me some time ago by Peggy Izzett. This is a good indication of occupation especially during the dry season when it stands out, often on hill-tops as distinct patches of yellow against the otherwise beige sea of grasses. So look out for this. I might add it is a useful indicator for locating sites on aerial photographs.  As to why this relationship occurs, it seems that this is an example of inadvertent change. This grass occurs individually almost everywhere, but after human activity it becomes concentrated on such sites. It would seem that the occupants have unwittingly altered the local soil conditions, possibly through its compaction and the addition of ash thus altering the pH and chemistry of the soil.  Only the Hyparrhenia seems able to tolerate this new regime and so it grows to the exclusion of other types. Once dominance has been established this continues for some time through its localised seeding pattern.  I might add that in eastern Botswana, Jim Denbow found that another grass, Buffalo Grass (Cerichrus citicris), acts in a similar manner.

Another interesting plant is the Aloe, especially the larger shrubby or tree-like species, eg Aloe arborescene and Aloe cameronii (both common around the Nyanga Ruin sites and the well known Aloe excelsea such as in the Valley Complex at Great Zimbabwe. These plants although they do occur elsewhere are frequently associated with stone walling. Why they grow in these walls I have often asked myself. Certainly some of the smaller species are short term colonisers of degraded land but what of these larger types? I doubt they have grown from seeds or cuttings in the household debris.  All too well one remembers the bitter aloe extract used to prevent pencil chewing at junior school, so I doubt they were eaten, but could they have been used as medicines or lotions? Suggestions much appreciated. One thing is certain, once established these plants thrive in the stone walls. Protected from grazing and fire damage they grow to enormous sizes, but in doing so it is true that they damage the walls by loosening the stones. Some of the wall problems at Great Zimbabwe are a direct result of the Aloe excelea, hence their recent removal.

Down in the Zambezi Valley, especially on the old river terraces at Mana Pools and Chirundu, I have noted a correlation between Baobab (Adonsonia digitata) and old Iron Age sites, which came first I cannot say; some of the trees are old and others comparatively young, but regardless of age of the tree it is rare to find a baobab without an adjacent site. Is it that the tree provided a focus for village life thus the village was built around it?  Are such trees tied to the ancestors as is the case in Zambia where the swollen trunk is residence to the souls of the departed? The younger baobabs around the sites are also of interest. Were they planted with the ancestors in mind or have they just seeded from household debris?

In the Nyanga area there is a strong correlation between “pit structures” and at least one of each of the following: White Stinkwood (Celtis africana), Wild figs (Ficus species), Erythrina species, and Cabbage Trees (Cussonia species). These trees are relatively uncommon away from the pits and they form an excellent indication as they produce a dense evergreen canopy which can be picked out on aerial photographs and as you stand on neighbouring hills. Why the relationship?

Well the figs are obviously derived from the seed of consumed fruits, but the others are less obvious. The Celtis is an excellent hardwood and may have been used in construction, although I have found its truncheons don’t grow very easily. As for the soft wooded Erythrinas and Cussonias I cannot say. Any suggestions?

Various other trees are known to be good colonisers, taking root in newly disturbed conditions and growing there until matters revert to pristine conditions when they tend to die out. Unlike the softer tissue colonisers we call weeds, certain trees also grow and are useful indicators due to their long living period. Good examples of these being the various Euphorbia species.  Tree Nettle (Urera tenax) and Acacia polyacantha . I doubt is any of these trees were directly planted or seeded from household debris, rather they arejust part of the natural ecological succession after human disruption. The Euphorbias are of particular use because they stand out due to their large size and colouration. So keep a look out for them when looking for sites.

In the Matopos one frequently finds several trees associated with occupied shelters. That is not to say they don’t occur elsewhere but other wise their concentration is far less obvious. The trees being Milkwood, Mimusops zeyheri, various figs (Ficus species) and Grewia species. These plants I believe are probably derived from seed of consumed fruit, edible fruit being a distinctive feature of each.

An opposite case to the above is the Mahobohobo (Uapaca kirkiana).  I have foundthat archaeological sites don’t occur in the vicinity of this species. The trees are obviously very intolerant of human interference. This is not to say they weren’t utilized for their excellent fruit, they just don’t seem to grow on sites unless it is particularly ancient. Thus don’t worry searching such places for you won’t miss much.

These are just a few of the relationships I have noted, there must be others.  What I have tried to show here is that plants can be used to find new sites, they’re not all just randomly scattered. Human activity will lead to the concentration or dispersal of certain floral species, and it’s this we need to discover. However, matters should not stop there, for inferences on the social behaviour can also be made eg the economy, building techniques and even abstract religious beliefs. Should you know of further information on these or other species please let me know as I am working on it at present.

-Rob S. Burrett, Acknowledged with thanks Newsletter No. 85 of Prehistory Society of Zimbabwe.



After writing the above I came across a most interesting article in New Scientist of 25.1.92, entitled “Archaeology takes to the skies”, it discusses how variations in vegetative cover, as indicated in aerial photographs, can be used to discover archaeological sites.  Work mostly seems to have been carried out in the America’s, but there are also references to classical Greece. Referring to it as phytoarchaeology, the author, 0. Joyce, discusses how human activities have affected the moisture, chemical and temperature of soils. This in turn has led to changes in the types and densities of certain plants, as well as the chlorophyll content of these plants. He discusses how their technique has been used to trace lost roads of the Maya Civilization in the Central American forests, and how by noticing the spatial distribution of scrub oak (Kermes) in the limestone areas of Central Greece, lost Greek tombs have been relocated.  So it is not just us amateurs that are looking at this subject of vegetation and archaeological sites. Any observations that we can make are not just academic, but will be of use to archaeologists in this Country.

-Rob Burrett .



The family MORINGACEAE has one tree representative in Southern Africa, that being the ‘moringo‘ Moringa ovalifolia of Central Namibia described in Coates-Palgrave as “a rather succulent tree up to 7 m in height with a strange squat swollen stem . . . with bark smooth pale whitish grey to almost coppery and shiny . ‘

Another species Moringa oleifera comes from India, but has become naturalised in N. Transvaal, parts of Natal, and the Zambezi valley. In India it is prized for its strong flavoured edible root, used also for medicinal purposes. Leaves are also edible. The article which follows was handed to Philip by an overseas visitor. As the Indian Moringo grows well here, there may be a great future for it here if there is someone to take up the challenge.


Plants do not often figure in research carried out by engineers. But this year, work featuring a hard, bean-like seed starred in the Engineering Council’s environment awards.

The seeds of Morinngo oleifera, a tree that is cultivated throughout the tropics and sub-tropics, form the basis of a water treatment process which could provide African villagers with clean, safe water when the seeds are ground and added to water, the particles bind to particles of dirt and other impurities in the water to form larger particles called flocs which are heavy enough to settle out.  Bound up in the flocs are bacteria and viruses that cause some of the worst of tropical diseases – typhoid, dysentery, “cholera and river blindness.

A group of scientists at Leicester University, led by Dr Geoff Folkard, has been trying out the process in Malawi in a project funded by the Overseas Development Administration. After shelling the seeds, villagers grind them in the large wooden bowls they would use to grind corn, and sieve the powder until it is as fine as possible.  Mixed with a little water, the solution is drip fed or pumped into the water supply.

No one is sure exactly how the Moringa seed works but Paul Williams, who designed the water treatment equipment says it is almost certain to be a protein in the seed. Certain types of protein molecules carry minute electrical charges which attract particles in the water in the same way that dust tends to stick to object. that have been charged with static electricity. The prototype treatment plant can provide clean water for 2,500 people.

The idea of using plant material to purify water is not a new one. Sanskrit writings several thousand years old mention the use of Moringa and other species for just that purpose. The tree is native to India and was transported to Africa as an ornamental by colonists in the nineteenth century. Moringa is a truly multipurpose tree, the kind so admired by economic botanists.  It grows fast and is both pretty and useful, the seeds, seedpods and young leaves are all edible in India the seeds are used in a type of dahl.

In addition to their work designing and testing the water purification system, the researchers at Leicester have been working with the Forestry Research Institute of Malawi to establish plantations of Moringa trees to find the best growing conditions for them.






Widdringtonia nodiflora. Photo: Bart Wursten. Source: Flora of ZimbabweBoscia foetida. Photo: Rob Barrett. Source: Flora of Zimbabwe