TREE LIFE
FEBRUARY and MARCH 2002
AS BEFORE PLEASE CONFIRM WITH ANY OF THE COMMITTEE MEMBERS THAT THE SCHEDULED OUTINGS AND WALKS WILL ACTUALLY TAKE PLACE. SEE THE BACK PAGE FOR PHONE NUMBERS.
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MASHONALAND CALENDAR
Tuesday 12 FebruaryBotanic Garden Walk. Please note the change of date owing to the Nyanga trip.
Meet in the car park of the Botanic Garden at 4.45 for 5 pm where we will meet Tom and continue with the Rubiaceae family.
Sunday 17th February. Cleveland Dam is the venue for this month’s outing. Lyn Mullin has found a delightful area in which to walk and a lovely spot for our picnic lunch which is quite secluded.
Saturday 23 February Mark’s walk is a return visit to a well treed area in the Ruwa area, – the home of Rick and Sally Passaportis, which was a very popular venue for the outing in June last year. Meet at the house at 2.30 pm.
Tuesday 5th March. Botanic Garden walk
MATABELELAND CALENDAR
There will be a trip organised by the Matobo Conservation Society to Tshangula cave in the southern Matopos on Sunday 17 February 2002. We will all meet at 9.00 at the Churchill Arms carpark, where lifts can be arranged if required. All members of the Tree Society are invited. Please bring your own chairs, food and drinks. Check with Jonathan Timberlake closer to the time about road conditions, but it should be accessible by normal vehicles.
No other arrangements have been made for February. Contact Jonathan Timberlake if you would like to organize a future outing.
TREE FLOWERING By Peter Taylor
The sparse flowering of jacaranda has been commented upon recently in Tree Life and Tree Life 262, December 2001 gives a Bulawayo record of Acacia galpinii and A. karroo not flowering at all.
In and around my apiary site in Banket, I have several Albizia versicolor which flowered prolifically in 2000 and set a mass of fruit, no doubt due to pollination from my bees. But this year they haven’t flowered at all. Is it possible that a heavy seed set inhibits floral initiation, the seed set perhaps being due, in part, to optimum moisture levels caused by several good rainy seasons in a row?
Suggestions and comments please!
NEW CONIFER FOUND IN VIETNAM
The following appeared on the BBC’s web site on November 25th, 2001.
An international team of scientists has found a new conifer in the forests of northern Vietnam. The tree, a new species in a new genus, has been named the Golden Vietnamese cypress.
Its discoverers say it is a missing link between true and false cypresses. But although it is new to science, the tree is already critically endangered, and only a few individuals exist.
The team that discovered the tree included scientists from the Royal Botanic Gardens, Kew, UK; the Vietnamese Institute of Terrestrial Ecology in Hanoi; the Komarov Botanical Institute in St Petersburg, Russia; and the Missouri Botanical Garden, US. They were in the area to study the orchids of the karst mountains of northern Vietnam.
The new cypress is a small tree with unusual foliage – the mature trees carry both needle leaves and a scale-like form, which are usually found only in juvenile individuals. The scientists made their discovery in October 1999, but waited till now to confirm it.
Kew’s conifer specialist, Aljos Farjon, told BBC News Online: “I was shown some slides of what they’d found, and I have to admit that at first I dismissed the possibility that it could be anything new. Then I saw a specimen. But I decided I needed to see another before I could make up my mind”.
The team went back to the area in February 2001 and brought back another specimen.
“I was excited to realize what it was, both for the sake of the new species and because it starts answering a few funny questions. The nearest relative of the new tree is the Nootka cypress of North America, itself a parent of Leyland’s cypress, known to gardeners and loathed by many of them. Now we may be able to find out why the Leyland, although a hybrid, is sterile.
Because we now know the Nootka cypress is not exactly what we’d thought, we’re having to give both it and the Leyland new scientific names. The Leyland’s new name is a bit shorter. Perhaps that will mean it stops growing so fast.”
The Golden Vietnamese cypress, Xanthocyparis vietnamensis, is the first new conifer found since the Wollemi pine’s discovery in Australia seven years ago. Before that, there had been no new conifers described since 1948. But Xanthocyparis is in trouble. It is naturally rare, found only on limestone ridges in a small area close to the Chinese border.
And the local people like to use its fragrant wood for building shrines and making coffins. Only a few semi-mature and coppiced trees exist. The golden cypress is the latest in a line of newly-discovered species in south-east Asia.
This month is the start of a fascinating story about our Baobabs compiled by Lyn Mullin. It will be spread over several months. The first part deals with the scientific information and some folklore and subsequent parts with folklore and other interesting stories and facts.
BAOBABS IN MY SOUP
Introduction
Adansonia digitata. Photo: Bart Wursten. Source: Flora of Zimbabwe
Very recently I received on loan a small book titled The Baobab in Fact & Fable, written by Rowan Cashel, a retired District Commissioner who died in July 1995. The book was produced and printed privately, and runs to 192 A5 pages, of which 32 are taken up by illustrations. I had had some correspondence with Rowan Cashel while he was preparing the book, and he was going to show me a copy, but he died before I could meet him. It was only the chance visit to an elderly friend in South Africa, the widow of another retired District Commissioner, that finally put the book into my hands.
There is much in Rowan Cashel’s book that might be of interest to readers of TREE LIFE, and summarized extracts from it, together with material from my own files and from other sources, will be combined into a single article on baobabs generally, but more particularly on our familiar African baobab.
It was noted Arab traveller, Ibn Batuta (1304-1369), who first brought outside attention to the African baobab. In his Rihlah, the account of his travels, he commented on a weaver in Mali whom he had seen weaving his cloth in the shelter of a hollow baobab.
The name baobab was probably derived from bu hobab or bu hibab – ‘the fruit with many seeds’ – the name the fruit was sold under in Cairo markets in the late 16th century.
Systematics
The genus Adansonia comprises eight species, six endemic to Madagascar, one to northwestern Australia, and one originally from continental Africa that has been dispersed widely by man within the tropics, including Madagascar where it has become naturalized.
Adansonia was named for French botanist Michel Adanson (1727-1806), who first came across baobabs in Senegal, West Africa. The genus is divided into three sections:
Section Brevitubae (2 Madagascan species) with erect, ovoid flower buds, and short, staminal tubes. A. grandidieri and A. suarezensis.
Section Adansonia (1 African species), with pendent, globose, flower buds, and long staminal tubes. A. digitata.
Section Longitubae (1 Australian and 4 Madagascan species), with erect, very elongated flower buds, and long staminal tubes. A. gregorii (Australia), A. rubrostipa, A. madagascariensis, A. za, A. perrieri.
There is some evidence to suggest that West African populations of A. digitata may be taxonomically separable from those of eastern and southern Africa.
Two of the Madagascan species have been divided into varieties. These are – A. rubrostipa (var rubrostipa and var fony), and A. za(var za, var boinensis, and var bozy).
Flower Colours and Flowering Period
Adansonia digitata. Photo: Mark Hyde. Source: Flora of Zimbabwe
A.digitata(white), A. grandidieri (white), A. suarezensis(white), A. gregorii(white), A. rubrostipa (yellow), A. madagascariensis(yellow or red), A. za(yellow), A. perrieri(pale yellow).
The flowering period of the two species in Brevitubae, A. grandidieri and A. suarezensis is in the dry winter months (May-September), and all the others flower in the wet summer months (November-March); A. digitata at the start of the wet season (which varies across its range); A. za, A. perrieri, and A. gregorii in the early part of the wet season (November-January); A. rubrostipa in the middle of the wet season (February-March); and A. madagascariensis flowers at the end of the wet season (March-April). The flowers open around dusk, and produce nectar for the one night only, although they may remain on the tree for 1-4 days.
Pollinators
There are two main pollinating systems in Adansonia, one carried out by nocturnal mammals, and the other by long-tongued hawkmoths, and these two systems are correlated closely with differences in floral morphology, phenology, and nectar production.
Proven pollinators of A. digitata are three fruit bats, Eidolon helvum (Straw-coloured Fruit Bat), Epomorphorus gambianus (Gambian Epauletted Fruit Bat), and Rousettus aegyptiacus (Egyptian Fruit Bat). Zimbabwe is in the migratory (but not main) range of the first of these bats; the Victoria Falls region as far as the upper limit of Lake Kariba lies within the main range of the second species; and the range of the third species covers all of Zimbabwe except the extreme west. The distribution of the three fruit bats coincides precisely with the distribution of A. digitata. In Madagascar there are also three fruit bats, Eidolon dupraenum, Pteropus rufus, and Rousettus madagascariensis. Fruit bats are believed to seek the nectar that is secreted by a ring of calyx tissue around the base of the ovary in all species; in sections Brevitubae and Adansonia the nectar is easily accessible, but there is restricted access to it in section Longitubae.
In Africa the Thick-tailed Bushbaby, Otolemur crassicaudatus, is also thought to be a pollinating agent since it feeds on the flowers of A. digitata, but some observers believe that this bushbaby is too destructive of the flowers to be an effective pollinator. In any case, the bushbaby’s distribution in Africa covers only a very small part of the baobab’s range.
Observations in Madagascar indicate that the two species of Brevitubae are primarily pollinated by nocturnal mammals, A. suarezensis by fruit bats, and A. grandidieri by the Forked-marked Lemur, Phaner furcifer, but bat pollination of this latter baobab could not be ruled out. Four of the five species of Longitubae, A. rubrostipa, A. za, A. perrieri, and the Australian A. gregorii are pollinated by long-tongued hawkmoths of the family Sphingidae. The fifth species of section Longitubae, A. madagascariensis, has not been sufficiently studied to provide reliable information on pollinating agents, but there is some evidence of minor pollination by honeybees.
Suggestions that sunbirds and ants also play a part in baobab pollination have not been supported by any positive evidence, although they are known to be regular visitors to the flowers in search of nectar. Other visitors to baobab flowers are bluebottles, at least three species of bollworm moths, flies, butterflies, and settling moths, but none of these is a known pollinator.
Normal Habitat
The African baobab is a component of the drier regions of Africa, with rainfall ranging from 200 mm to 800 mm annually, but there is no doubt that its currently mapped range in Africa includes areas that have been extended by man. Its importance as a source of food, water, and raw material for various products would have ensured its dispersal by man and animals throughout much of sub-Saharan Africa.
In Zimbabwe the baobab is an inseparable part of the Zambezi Valley and the Save-Limpopo lowveld at altitudes up to 600 m, but it does also occur in other, less likely, areas, eg the single specimen just outside Kadoma on the road to Gweru, the occasional specimens in the Kalahari-sand regions of northwestern Matabeleland, and the population in the Nyanga North region growing naturally at an altitude of more than 1200 m. The highest altitude that has been recorded for a naturally growing baobab in Zimbabwe is 1330 m in the Nyanga North area; the observation was made in 1951, but the tree has long-since died and disintegrated.
Baobabs have been planted well outside their natural range both in Zimbabwe and elsewhere. The National Botanic Garden and Greenwood Park in Harare contain some thriving specimens, and there are two trees at No 14 Arcturus Road in Highlands at an altitude of 1520 m. Baobabs were successfully grown in England as long ago as 1720, reaching heights of more than 5 m before the severe frost of 1740 killed them all.
In Australia the baobab (or boab as it is called) is confined to open woodlands of the Kimberley region of the north of Western Australia and the northwest of Northern Territory. The latitudinal range is 14-18S, and the altitudinal range is from near sea level to 400 m. The mean annual rainfall is 500-1500 mm, with a long dry-season.
Baobabs in Masdagascar extend from the extreme north to the extreme south of the island, in the dry region west of the central mountain chain. They are usually canopy or emergent forest trees of the lowlands, but A. perrieri grows in rainforest at altitudes of up to 650 m. At the other extreme, A. madagascariensis, A. suarezensis, and A. rubrostipa can all be found in coastal scrub that may occasionally be inundated by sea water.
- A. perrieri and A. suarezensis face extinction in the foreseeable future due to degradation of habitat by human activity.
Size Attained by the African Baobab
The African baobab is probably the largest of the eight species of Adansonia. It is certainly very much larger than the Australian species, which reaches heights of 12-25 metres and diameters of up to 6 m. No data have been seen for the Madagascan baobabs (except for A. perrieri, which may exceed 25 m in height), but photographs suggest heights and diameters comparable with those of the Australian species. Reliable reports of African baobabs with diameters of 10.82 m and 10.64 m have come from Sudan and South Africa, respectively, but unconfirmed reports of diameters of 17.7 m and 17.35 m have appeared in the Guiness Book of Records. Attempts to verify these records have met with no response. In Zimbabwe the largest known diameter for any baobab is 8.79 m for a tree on Devuli Ranch in the Save Valley, and the tallest height is 27 m for another tree in the same area. The pre-storm-damage height of 47.5 m recorded by Rowan Cashel for the ‘Big Tree’ at Victoria Falls is clearly erroneous. This tree was said to have been truncated by a violent storm in 1960, but there is no way that a claimed height of over 47 m could be accurate. Such heights belong to rainforest trees, not to trees of dry-country woodland. In 1985 the ‘Big Tree’ at Victoria Falls had a diameter of 7.02 m, and the height of 24 m was very much in proportion to the diameter.
Age
Here we enter the realm of speculation, but it might not be wildly inaccurate to suggest an age of 3000 years for a really big African baobab. Carbon dating of a tree of 4.5 m in diameter from the Kariba Basin was carried out by Dr ER Swart at the (then) University of Rhodesia and Nyasaland, and he came up with an age of 1010 years 100. If this is used as a yardstick, a tree of twice that diameter could well be three times the age, because diameter growth cannot possibly be maintained at the same rate throughout the life of a tree – even if the same volume of wood is produced each year (see also the contribution by GL Guy in Rowan Cashel’s book).
The first attempt to calculate the age of a baobab was made by Michel Adanson when he examined two trees in Senegal in 1749, and concluded that they were 5150 years old. Some 100 years later this infuriated David Livingstone, who belonged to the school of thought that had calculated the Year of Creation as 4004 BC. Adanson’s calculations put these trees on earth before the Great Flood, and what annoyed Livingstone was the inference of no Flood! But when Livingstone himself set about dating a large old baobab, he arrived at a figure of over 4000 years!
The Tree of Plenty
Practically all parts of the African baobab are used by man. The roots provide a red dye, and can even be eaten; the bark fibre is used for making mats, baskets, clothing, and medicine; the leaves make a good substitute for spinach, and they can also be used medicinally; the pith surrounding the seeds may be mixed with water to make a refreshing drink, or it can be used as a substitute for cream of tartar; and the hard pods have many domestic uses.
The story is much the same for the Madagascan baobabs. A. rubrostipa provides mushrooms from the fallen trunks; the hollow trunks of A. grandidieri and A. za are used as water cisterns; the bark of the latter two species is used for rope; the sap of A. grandidieriis drunk fresh; the wood of A. grandidieri and A. rubrostipa is used for thatching huts, that of A. grandidieriis burnt as fuel, and that of A. grandidieri and A. za is fed to cattle; seedling roots of A. grandidieri, A.madagascariensis. A. rubrostipa, and A. za are eaten; the fruit pulp of all species is eaten fresh, and is also thought to be used medicinally; and the seeds of A. grandidieriare eaten fresh, and an oil is extracted from them.
In Australia the boab is important to the Aboriginal people. The pulp is eaten dry, or mixed with water as a beverage; the trees are sources of water, just as they are in Africa and Madagascar; the bark is rolled to form twine; a gum was traditionally made from the pollen, and was said to be used for fixing heads to spears; and the fruits are carved as ornaments. An early observation from Australia was that the Aborigines used to carve marks on boab stems, apparently to record the number of fruit taken.
Hollow trees in Africa have provided water-storage reservoirs from time immemorial, and a large tree can hold up to 900 litres. No wonder, then, that old slaving and trading routes followed a path from one hollow baobab to another across vast arid tracts. In more modern times hollow baobabs have been put to a great variety of innovative uses – bus shelters, cold rooms, dairies, dwellings, flush toilets, jails, storerooms, tombs, and probably many more.
DR LIVINGSTONE’S MONOGRAM, I PRESUME
Or
A SECOND PIECE OF VANITY
I could hardly believe my eyes when I first spotted it hidden away in the dark interior of an enormous hollow Baobab tree standing on the southern bank of the lower Zambesi, deep in Portuguese East Africa. It seemed too incredible that no one had ever spotted it before.
QUENTIN KEYNES –
DR LIVINGSTONE’S MONOGRAM, I PRESUME
In a chapter contributed to Rowan Cashel’s book by Quentin Keynes, the author describes finding David Livingstone’s monogram carved into the bark of the inside of a hollow baobab. The authenticity of the find was verified by David Livingstone’s grandson, Dr Hubert Wilson, who was shown a flashlight photograph of the monogram, the characteristically looped ‘D’ and ‘L’ of the missionary-explorer’s signature.
It all started with Keynes’s chance acquisition in an auction of a four-page letter written by Livingstone on 25 May 1859, and deposited ‘in a bottle ten feet Magnetic North from a mark + cut on the beacon.’ This acquisition started Keynes on a decision to retrace the explorer’s six-year Zambezi Expedition of 1858-1864, and in this he was accompanied by two friends.
The search eventually led to a Senhor Ferrao, whose grandfather had known Livingstone well. Ferrao mentioned a hollow baobab where Livingstone had camped near Shiramba, and Keynes narrates –
It was about three miles above Shiramba, and an immensely wide baobab, easily distinguished from others along the way by a narrow slit in its trunk. The slit provided a doorway taller than a man, and all three of us were able to walk upright through it into the tree’s dark interior. Here we found a perfect natural shelter, which I estimated to be over 30 feet high and perhaps 30 feet around.
Excitedly I peered around for initials. There were several newly made ones, and some indistinct – rather older – marks. But nothing that looked remotely like ‘D.L.’ Then I turned to face the entrance way – and there, a foot or so from the edge of the slit, was the mark that I immediately deciphered as the work of David Livingstone from the characteristically looped ‘D’ and ‘L’ of his signature that I had long since noted on my bottle letter. I could see it had been cut a long time ago from the blackness of the indentations.
“Dr Livingstone’s monogram, I presume?’ I said to my astonished companions.
In camp that night I searched through a printed copy of the explorer’s Zambezi diaries, and found an entry that clearly and indisputably confirmed my discovery. Under the date September 16th, 1858 – it was now August 1958 – I read:
“We wooded at Shiramba, about four miles above the spot pointed out as the great house�I walked a little way to the southwest and found a baobab which Mr Rae and I, measuring about three feet from the ground, found to be 72 feet in circumference. It was hollow and had a good wide high doorway to it. The space inside was 9 feet in diameter and about 25 feet high. A lot of bats clustered about the top of the roof and I noticed for the first time that this tree had bark inside as well as out.”
It seems evident from the last sentence that Livingstone had been playing around with his penknife on the inner surface of this strange hollow tree, and that he had, probably without thinking much about it, soon manufactured his perfect monogram.
This contribution by Quentin Keynes raises the question: Did Livingstone further indulge his vanity by carving his initials or monogram on any other trees? It would certainly seem that when he ‘indulged in this piece of vanity’ on Livingstone Island in 1855 it was not to be the last time that he did so!
SORORO’S TREE
The following story from Rowan Cashel’s book was contributed by NJ (Jack) Brendon, a retired District Commissioner.
Many baobabs provide shelter to the tribesman, like the one known as ‘Sororo’s Tree’. This giant stands alone beside a path in the Mutoko District of Zimbabwe’s northeast, and the people of that area would spend a night in its roomy interior when they were travelling. It is big enough to accommodate 20 or more, and the trunk has a natural doorway plus several holes that serve as ventilators. One evening a man named Sororo was travelling through the country with his wife and three children. They reached the tree at about sundown, and as it was too late to travel on to the safety of the next village, they decided to spend the night in this recognized resting place. They made a small fire, and the woman roasted some monkey-nuts, then, having finished their meagre meal, the family lay down to sleep.
They were tired after their long journey, and did not stir when the fire grew cold. It was then that the lion arrived. He was old, and was worried by the quills he had received in his foreleg a month or so before when he had tried to kill a porcupine. He had tried to bite these quills from his leg, but had only succeeded in making matters worse, and now he was painfully lame. Often during the past year he had gone hungry, and now his recent injury had prevented him from killing for several days. As he passed the baobab a slight scent of humans wafted towards him. Hunger drove out any natural fear that he might have had. He prowled slowly round the tree, then saw the opening, and went inside.
It was some days before the fate of the travellers was discovered, and then the engorged animal was tracked down and shot. Since then the tree has been shunned as a place of refuge. Charms and an ornamental axe were found in the tree some months later, and this gave rise to the rumour that a witch had taken up residence in the dark interior.
To be continued.
In Retrospect by Lyn Mullin (Cont).
SYSTEMATIC ARRANGEMENTS
A ROOTNOTE from Kim Damstra in TREE LIFE No.118 (December 1989):
Everyone seems to understand basic zoology. If asked to arrange a frog in the progression jellyfish, shark, lizard, bird, they will put the frog between the shark and the lizard. But if asked to put the Bignoniaceae (jacaranda family) into the sequence Strelitziaceae (strelitzia family), Caesalpinioideae (cassia family), Rubiaceae (gardenia family), they fall apart, as if they were being asked to translate ancient Arabic. And yet it is not very difficult, certainly not beyond any of us, if we know three easy rules:
(1) All parallel-veined leaves (eg strelitzia) are conventionally placed before net-veined leaves (cassia, gardenia, and jacaranda).
(2) Net-veined leaves with separate petals (think of a cassia flower) are placed before fused petals (visualize a tube-like gardenia and jacaranda).
(3) Fruit that sits below the flower (remember a gardenia, where the remains of the flower remain on the end of the ripening fruit) is considered a more advanced feature than fruit that develops within the petals (as in a jacaranda).
So, on this basis, the Bignoniaceae (jacaranda family) falls between the Caesalpinioideae (cassia) and the Rubiaceae (gardenia).
One eventually gets to know where to find the biblical books by their “almost” chronological sequence, yet, as we are always consulting books like “Trees of Southern Africa” (Coates Palgrave), it will help us a lot to get a basic idea of how things are arranged – it will also open up the arrangements in most of our southern African herbaria, which follow the arrangement of the botanists Engler and Prantl. This is not a real classification, and does have a couple of flaws.
Mail a cheque for $400, made out to the “Tree Society” to PO Box 2128, Harare giving full details of your name, postal address and email address and you will be including in the mailing list pending confirmation of acceptance of membership.
MARK HYDE CHAIRMAN
