November 2009


Sunday 15th November: Ruzawi School, near Marondera.

It has been about two years since we last visited Ruzawi.  There are always interesting species to see in the high-rainfall miombo woodland typical of that area.  Once again our hosts will be Maureen and Buck Williams.

Sadly, Maureen and Buck will soon be leaving for New Zealand.  Please can everyone make sure that they bring a cup for tea as Maureen tells me she has sold a lot of hers!

Directions: From Harare, take the road to Marondera.  Within the town, turn right at the Shell Garage (Ruzawi Service Station).  Travel for approximately 5 km. Turn right where it says Ruzawi School and also St Cyprians.  You are now on the Ruzawi Road.  Turn right to front gate, then immediately left inside the gate.  You will arrive in the Williams’ garden.

Meeting time: 9.30 a.m.  Please bring a chair and packed lunch.

Note:  There will be no walk with Tom this month as he is away.


October – Jacaranda month

Recently there was a discussion on the age of jacarandas.  The age of trees is a perennial question so I decided to see what Lyn Mullin in Historic Trees of Zimbabwe had to say on the subject, and most of the information comes from that source.  I also used The Plant Book by D.J. Mabberley.

According to Cabbages and Kings in The Herald of 17 December 1958, Zimbabwe’s first jacaranda was planted in 1899 or 1900 in the garden of what we used to know as 13 Montague Avenue and, as Montague Avenue was previously called Cape Avenue, it was probably called that when the jacaranda was planted there.  So street names were changed even in those days.  What was known as 13 Montague Avenue is now 23 Josiah Chinamano Avenue.  When Jacaranda Mews was built on that stand, this jacaranda was preserved and was in the grounds of no 5, where there used to be a plaque which stated ‘This is believed to be the first jacaranda planted in Salisbury or Southern Rhodesia – circa 1900’.

Had it survived it would have been 109 years old now but the Queen didn’t need to send it a telegram in 2000 because, unfortunately, it didn’t make 100 years, as it collapsed in 1998.

Josiah Chinamano Avenue is lined on both sides by jacarandas which were planted in the rainy season of 1902-1903.  This jacaranda-lined avenue extends for two kilometres, from Tenth Avenue to Prince Edward Street and was called Montague Avenue after Sir Ernest Montague who came to this country in 1898 as a clerk in the BSA Co.  He rose to become Secretary of Mines.  For many years he was an active chairman of the Tree Planting Committee in Salisbury’s early days and was probably responsible for the tree-lined streets of present-day central Harare.  The avenue no longer commemorates his name.  But the two lines of jacarandas are still there.

While we are still in Josiah Chinamano Avenue, in fact in the same block that the first jacaranda was planted, the first flamboyant was planted between Leopold Takawira (previously Moffat Street) and Blakiston Streets and now stands in front of Alderbury Court.  It is a bit of an odd man out – apart from being a totally different species, it is out of the line of the row of jacarandas.

While history does not seem to relate who planted the first jacaranda, it was probably Milton, who introduced the first flamboyant.  Whether he planted it or not, I don’t know.  He was Secretary to Cecil John Rhodes and came to this country in 1896 as Chief Secretary for Native Affairs, becoming Senior Administrator of Rhodesia two years later.  He was a very keen gardener and was known to have distributed flamboyants to his friends.  Who actually planted that tree reputed to be the first?  The history that I have does not relate.

The jacaranda, Jacaranda mimosifolia, comes from Brazil.

The flamboyant, also known as the peacock flower or flame tree, was originally known scientifically as Poinciana regia but has been placed in a different genus and is now Delonix regia.  It comes from closer to home, Madagascar, where it is now very rare in the wild.  In fact, I think it is thought to be extinct there but was rediscovered in 1932.  So perhaps it is a good thing it has been planted in other parts of the world.  It actually belongs to the same family Caesalpiniaceae as our Brachystegia and Julbernardia.  Here in Harare one of the streets where the flamboyants are famously spectacular is Blakiston Street.  They usually come into flower in November, heralding – we hope – the beginning of the rainy season and for the children the approach of Christmas.  They tend to be not very tall and are flat-topped with the flowers borne on the top of the tree and are best viewed from above.

Spathodea, or scientifically Spathodea campanulata, also known by many common names including flame tree, African tulip tree, fountain tree and Nandi flame is another of our spectacular flowering street trees.  This comes from even closer to home, it occurs naturally in East Africa and I found it quite exciting to see it growing in the wild in Uganda.  It also occurs in Kenya.  Lyn Mullin has not included that in his Historic Trees of Zimbabwe, so I don’t know who was responsible for introducing it into this country.  Both the jacaranda and the Spathodea belong to the same family Bignoniaceae.

Here they have no natural pests and have flourished.

Unfortunately, both the jacaranda and the Spathodea have wandering tendencies and do not always stay where they are put.  I once worked at Bumi Hills where Spathodea had been planted.  The baboons enjoyed the pods and seeds, and we had to be very watchful of the trees coming up in the bush.  We only became aware of this when they came into flower.  Jacaranda seeds are wind-blown and have found their way too many places where they ought not to be.

I am afraid I am a purist when it comes to aliens invading our indigenous woodlands and forests.  You just have to look at Nyanga to see how the pines and wattles have invaded the area.  And on Sunday coming back along the Mutoko road there was a place where the jacarandas had invaded right up a gulley.  And there are many instances around the country where they are visible in the bush at this time of the year.  As gardeners, we all know they are greedy feeders.  I agree the jacaranda is very beautiful in flower and also in autumn colours just before the leaves fall and I believe the wood makes a very fine timber, but I do have strong reservations about its presence.  In fact, in South Africa it has been declared a weed and may not be planted and efforts are being made to eradicate it where possible.

Unfortunately, the early generations, including my parents, thought if a tree was indigenous, it was of no value and should be replaced.  And so far too many indigenous trees were removed and far more alien trees than necessary have been planted.

In fact, what is now Harare was probably miombo woodland before the establishment of the settlement in 1890.  There are occasional msasas still standing, including the one in Josiah Tongogara Avenue near the intersection with what was previously known as Second Street.  Apparently when this tree was depicted on a postage stamp issue in the 1990s, it was called a hanging tree and it is amazing how many people know it as that, but the information is probably incorrect as there appears to be no evidence of it’s ever having been used for such a purpose.

There is a record of a hanging tree in Bulawayo from which nine people were hanged during the 1896-97 hostilities.  This is what is known as the false marula, or Lannea schweinfurthii.  It stands, if it is still there, unmarked, on the east side of Main Street between First and Masotcha Ndlovu Avenues.

And while we are in Bulawayo, Lobengula had two royal kraals and two indaba trees—both Pappea capensis—unsurprisingly commonly known as the Indaba tree in Zimbabwe.  These were known as indaba trees because that was where Lobengula held court.  The first one at his first royal kraal, a Gubulawayo, now known as Old Bulawayo about 18 km southeast of present Bulawayo, and the second on the site of the present-day State House.  Whether the presence of that tree influenced his choice of the second site, I really don’t know.  The second Indaba tree became a national monument having escaped the burning of the great kraal when the king fled following the defeat of his army.  It subsequently suffered considerable die-back and much of the stem is now in the Bulawayo Museum.  Like so many of our indigenous trees, it has been able to produce root suckers.  This was recorded in 1987 so hopefully it has regrown.

The first indaba tree suffered a totally different fate.  It was strangled – by a strangler fig, Ficus burkei, and died in 1960.  But the fig is still there and stands in its place.

Figs are amazing trees.  They have three types of habit and growth form.  Firstly, there is the strangler fig which starts life as an epiphyte, in other words, growing on the host tree but taking no nourishment from it other than a bit of compost from the bark.  The seed, having been deposited in the fork of a tree germinates and sends down long aerial roots which twine round the host until eventually they reach the ground when they become the true roots.  The aerial sections criss-cross and fuse by natural grafting, expanding, thickening and strengthening until they form a pseudo-trunk around the host tree and can literally squeeze it to death by destroying the phloem, which is just under the bark.  In other words, effectively ring-barking it.  Trees have their phloem, the food transporting vessels, just inside the bark, so if a tree is ring-barked the food supply system is cut and the tree dies.  Trees also have the ability to expand their trunks in proportion to their height.  The xylem cells, which are the water transporting vessels, increase in number each growing season, forming the rings in the wood so they are expanding outwards increasing the pressure from the fig tree.

In the Kibale forest, Uganda, we looked at a strangler fig growing on a wild date palm, Phoenix reclinata, but the palm had not been strangled.  Palms have the xylem and phloem in what are known as vascular bundles, which are not able to increase in size.  Palms cannot start growing upwards until the stem is wide enough to support itself and the limited number of leaves it bears.  So, if the roots of a fig wrap themselves round a palm, it does not die.  Of course in the forest the palms are competing with all the other trees for the light so have grown really nice and tall and make really nice long poles.

Other species of Ficus tend to grow on rocky outcrops.  They probably have a thin bark and in the rocks are protected from fire.  Their roots creep, tightly pressed, against the bare rock-faces, squeezing their way into almost imperceptible crevices and cracks until even great boulders can be split apart.  These are called the rock-splitting figs.  There are wonderful examples of rocks which have split by fig trees in the Sanyati gorge at Kariba.  Because the roots have been squashed in the rock crevice when the rock splits and breaks, the roots look as though they have been sploshed against the rock.

Thirdly, many species grow as ordinary trees or shrubs, and even those which tend to be stranglers or rock-splitters can grow as normal trees if they happen to have established themselves in open ground.  In Oak Avenue in Mutare there is a magnificent example of a strangler fig now standing on its own surrounded by a forest of its own aerial roots.  This is Ficus rokko.  There is also one in the Botanic Garden.

Meg Coates Palgrave

October 2009


Who says it’s green to burn wood chips?

Woodchip power stations are set for a boom.  But conservationists are increasingly challenging their green credentials.


One of the most cherished articles of faith of the green movement – that wood-fuelled power stations can help save the planet – is being increasingly challenged by campaigners and conservationists around the world.

Electricity generated by burning woodchips is on the verge of a global boom.  America is planning 102 power stations fuelled by woodchips in the next few years.  Europe is reported to be planning a similar, if yet unquantified, expansion.  And in Britain, the next three years will see wood-fuelled power station capacity increase sevenfold, requiring, according to the campaign group Biofuelwatch, so much timber that it would need an area 12 times the size of Liechtenstein to grow it.

The power companies say the source will be “sustainable forests”, but campaigners and ecologists claim that untold damage will be caused by the burgeoning market for wood.  They say that, although traders in the developing world are being tempted to grub up and sell native forests, the chief danger is in the creation of monoculture plantations, where single species of trees are grown in straight rows and little wildlife can establish a home for itself.

They also challenge the “green” assumptions behind woodchip power, claiming that, far from fighting climate change, transporting large amounts of bulk wood across oceans and then burning it will increase carbon discharges by 50 per cent more than would have been caused by burning a fossil fuel like coal.

The power companies dispute the campaigners’ science, and most also insist the wood will come from “sustainable sources”, as approved and certified by the Forestry Stewardship Council.  This non-government body said: “The FSC does not support the conversion of natural forests into plantations.”  But it added: “Certification may be granted if the forest manager can demonstrate that they were not responsible for the conversion.”

Such flexibility is now drawing fire.  A recent article in The Ecologist, headlined “Can we trust the FSC?”, read: “The World Rainforest Movement reports that by 2008 the FSC had certified 8.6 million hectares of industrial tree plantations ‘despite ample evidence regarding the social and environmental unsustainability of large-scale monoculture tree plantations’ ….  Jutta Kill, climate campaigner at the Forests and European Union Resource Network, says, ‘There is a long continuum between an intact forest and short rotation monoculture tree plantation on the other end.  It is preposterous to claim these are the same.’”

The FSC claims, however, that “properly managed plantations are essential to stop the destruction of natural forests”.

The issue may yet prove just to be a panicky reaction to a radical expansion of wood energy or it may be a portent of a deep problem.  If so, it will echo the evolution of biofuels, initially embraced as a universal blessing before it was realised that native forests were being grubbed up to grow palm oil, and that US farmers would switch from food cereals to fuel cereals, thus causing a world food shortage.

Some campaigners are in no doubt.  Almuth Ernsting from Biofuelwatch said: “It’s almost unbelievable that we’re creating vast areas of monoculture, mile after mile, just to be cut down as fast as they grow, to be shipped thousands of miles to be burned just for people’s electricity.  It just doesn’t make sense.  What about all the habitat that gets destroyed along the way?”

Simone Lovera, of the Global Forest Coalition in Paraguay, said: “Europe is going to cook the world’s tropical forests to fight climate change; it’s crazy.”  She said her group had obtained a report stating that Brazil is gearing up to meet the European woodchip demand, not by cutting down forests, but by expanding tree plantations by 27 million hectares, mostly of exotic species such as eucalyptus.

Last week, at the UN-sponsored World Forestry Congress in Buenos Aires, the agronomist engineer Hector Ginzo, an adviser to the Kyoto Protocol, stressed that plantations could not be classified as sustainable.  He said UN rules “would never allow a plantation of eucalyptus or other fast-growing trees for use as pulp or wood to be considered a sustainable forestry project, because that kind of production favours monoculture forests and the carbon capture is lost when the trees are cut down”.

The Global Forest Coalition said that, in South America, tree plantations have had devastating effects on people and the environment, and have nothing like the biodiversity or ecological function of natural forests, whether they are first or even second growth.  These plantations, it said, are “green deserts” because of the amount of water they consume, and because of the lack of native wildlife.

Isaac Rojas, co-ordinator of the forest and biodiversity programme at Friends of the Earth International, said: “All over the world, plantations destroy the lands and livelihoods of local communities and indigenous peoples, as well as biodiversity and water resources.  They also store less carbon than natural forests.”

FoE International and the coalition now want the UN’s Committee on Forestry to stop promoting plantations and to urge governments immediately to halt the conversion of forests into biofuel plantations.  A UN report issued in March noted that the expansion of large-scale monocultures of oil palm, soy and other crops for agrofuel production has been a major factor in the failure to halt deforestation.  It added: “The potential for large-scale commercial production of cellulosic biofuel will have unprecedented impacts on the forest sector.”

Janet Larsen, director of research at the Earth Policy Institute said: “Shipping chips like this is just not the answer.  We have been warning about this for some time now Wind turbines and solar power make much more sense.  You need to source biomass from relatively small areas around power plants.  Here in the US you can drive for an hour and never see more than one species of tree.  We used to have far more natural forest than we have now.”

She said the institute had now discovered land in Laos being bought by China to turn into plantations.

The Global Forest Coalition said an examination of international trading companies has revealed a new and growing global industry in wood for energy.  UK campaigners at Biofuelwatch said that wood chips and pellets are now being imported from South America, the US, Canada, Portugal, South Africa and Russia, among others.  It has also discovered that Mag-Forest, a Canadian company operating in Congo, is starting to ship 500,000 tons of woodchips annually to Europe.  The Independent on Sunday was offered 100,000 tons of tropical hardwood and softwood a month by a firm in Ghana and a British firm is negotiating over supplies from Indonesia, home to some of the world’s richest rainforests.


‘Burning wood is called carbon-neutral, but it’s not’

Rachel Smolker

Global Justice Ecology Project


In Europe, small-scale woodchip power plants make use of locally harvested timber and wood waste.  In the UK, a government strategy paper on waste said that recovering energy from the two million tonnes of the waste wood available could both generate electricity and save over a million tonnes of CO2 emissions.  But such sources will not be able to feed the industry’s huge need for wood in convenient bulk deliveries over the next few years.  Worldwide, production of wood pellets is set to double in the next five years from the present 10 million tonnes to 20 million.

In recent months, British power companies have said they will build at least six new generation plants to produce 1,200 megawatts of energy, most by burning woodchips.  The country’s demand for wood will increase more than sevenfold.  MGT Power, which is creating a new waste-to-energy plant at Ince in Cheshire and a new woodchip-fired power plant at Teesport near Middlesbrough, then another in North Shields, will be using chips from North and South America.  It said it will use crops planted specifically for use as fuel, examples being eucalyptus, pine, willow and poplar.  A company statement insisted that it “will never procure fuels that contribute to the loss of areas of protected habitat or areas of high ecological value”.

One of the new plants – the world’s largest – is now being built at Port Talbot in South Wales, and by 2012 it will supply over half Wales’s one million homes, and, claim its owners, Prenergy, displace 3.5 million tons of CO2 emissions a year that would have been produced by older power stations.

The fuel will arrive by sea, largely but not exclusively from America.  A company statement said: “Prenergy is committed to obtaining its feedstock from a range of overseas sources.”  This, it added, would “take advantage of a variety of species with rapid growth rates, and lower delivered moisture content due to rapid post-harvesting drying achievable in more southerly latitudes”.  The company said its studies had shown that the carbon emitted during shipping of the woodchip represents only about 2 per cent of the total carbon being transported.  Other plants are planned for Drax, Anglesey and Teesside, which together will burn 20-30 million tons of wood a year.

Biofuelwatch said: “The land area needed to grow the biomass to power a station the size of Port Talbot ranges from 130,000 to half a million hectares of productive land – an area three times the size of Liechtenstein.”

The power firms claim that generating electricity by burning wood emits an equal or lesser amount of CO2 than the quantity absorbed by the trees through photosynthesis in forests.

The claim, however, has been robustly denied by Rachel Smolker, a research scientist who works with the Global Justice Ecology Project in the US.  She said: “Burning wood is called carbon-neutral, but it’s not.”

She says that research by the Massachusetts Environmental Energy Alliance, a US environmental group, indicates that burning trees for energy produces 1.5 times as much carbon as coal and three to four times more than natural gas.  She added: “Climate change is a huge problem, but some of the plans for fighting it are even more dangerous.”

Graham Mole

Originally published in The Independent on Sunday (UK) on 28 October 2009.  Republished in the interest of science.


Outing to Ewanrigg National Park

18th October 2009

Ewanrigg lies approximately 30 km north of Harare, on the Shamva road at 17° 41.805’ S and 31° 19.757’ E at an altitude of 1298 m.  This national park lies in a rolling hilly area formed by basaltic rocks, with red loamy soils.  Most of the area was originally miombo woodlands, much of which has been cleared for agriculture and the gardens within the park.  Twenty people attended the outing.  Thanks to our leaders Mark Hyde and Meg Coates-Palgrave.  Mark led a group of 6, and Meg led a group of 14.  This report is from Mark’s group.

The Miombo woodland was dominated by Julbernardia globiflora with lesser Brachystegia boehmii and occasional Brachystegia spiciformis.  Three separate environments were noted.  First, the managed planted gardens, second, typical open miombo woodland near the picnic area.  Thirdly, a most interesting forest-like closed miombo woodland at the base of a hill.


The extensive mowed and originally cleared garden lies in a well drained basin surrounded by low hills.  The trees, and groups of trees, are long established, and well spaced.  A fine old Msasa, Brachystegia spiciformis, left from the original clearing, dominates the garden area.  Although not in new red leaf, it is a magnificent sight.  An unusual feature of this garden was the sense of space between the large trees.

A tall, rather than spreading, Kapok tree, Ceiba pentandra of the Bombacaceae family, had well-developed buttresses and the ground under the tree was covered in an ankle deep carpet of leaves.  The leaves, as the name pentandra indicates were five-fold digitate.  In its native habitat in the tropics of America, Africa, and the East Indies, this tree can grow to 50 m or more.  Gmelina arborea is a member of the Verbenaceae family.  It is native to India, Bangladesh, Sri Lanka, Myanmar, Thailand and southern China.  Its common names are Gmelina, Kashmir tree, White beech or White teak.  It has brown and yellow orchid-like flowers, and at the base of the leaves is a distinctive double gland.  This fast-growing deciduous tree is a popular plantation tree in the tropics where it prefers moist, fertile valleys.  Its light but strong cream-coloured timber is often used for musical instruments.  Enterolobium contortisiliquum is a native of Brazil.  A member of the Fabaceae family, the trees had white Albizia-like flowers, and it still carried a few of the distinctive pods which give it its common name, Rattle-pod.

Among the exotics were several planted indigenous trees, including, Sterculia quinqueloba, Syzygium guineense subsp. afromontanum, Stereospermum kunthianum, and in bloom, Albizia amara and Acacia nigrescens.

Miombo woodlands

Near the parking area was a typical open section of Miombo woodland.  Here the main tree was Julbernardia globiflora.  Other trees recorded were Uapaca kirkiana, Vernonia colorata and Faurea rochetiana.  The grass that had been growing under the trees had been burnt off, and the following pyrophitic suffrutex were recorded: Sphenostylis erecta subsp. erecta, Dolichos kilimandscharicus subsp. kilimandscharicus and Ochna richardsiae.  These plants are typical of an area subjected to repeated annual burning.

Across the garden from the parking area was a most unusual section of woodland.  The different nature of this woodland had been noted by Dave Hartung on a previous visit to Ewanrigg, and to check out this area of woodland was the main reason for our outing.

The dominant tree in the woodland, as in the rest of the local area, was Julbernardia globiflora.  However, the canopy was much more closed and forest-like, compared to other local sections of woodland.  No grass was seen on the ground; instead it was covered with an extensive bed of leaf litter.  The base of this leaf litter was moist and well rotted, and penetrated by feeder roots.  The only suffrutex seen was Sphenostylis erecta subsp. erecta.  These were not well developed, but spindly and weak-looking.  Quite clearly, a bushfire in this area is an uncommon event, unlike most typical areas of Miombo woodlands.  Mostly the trees seen here are the kind of woodland tree normally found in the local area, but some such as Celtis africana and Syzygium guineense subsp. afromontanum do not like being burnt.  Syzygium guineense subsp. afromontanum almost certainly was seeded from the planted tree in the garden.  Diplorhynchus condylocarpon did not occur as a tree, but as a liana, causing much confusion in its identification.  Another problem tree was Acacia gerrardii, only positively identified from a pod found on the ground.  Pleurostylia africana and Euclea schimperi both proved difficult to identify, the former due to its very variable leaf form in this woodland.  Zanha africana was leafless and bearing immature fruit.  A fine old specimen of Securidaca longipedunculata was in full flower.  Normally a tree with smooth pale grey bark, this tree had black grooved bark at the base.

 Escapees seen were Prunus cerasoides and Lantana camara.

What explanation can be offered for this forest-like woodland?  Often, especially in granite areas where there is high runoff from rainfall on steep rocky slopes, a dense area of bush can be found at the base of the slope.  I feel that this is not the cause in this case.  In my opinion, the cause is due to the absence of bushfires over the last 50 to 70 years of the park’s existence, resulting from management fire prevention policies, and the fact that gardens, buildings and roads created firebreaks, which, quite by chance, protected this area.

Name changes

Some of us lesser mortals really battle to retain in our memories the various scientific names of plants.  All too often due to ongoing revision of names of everything the name of a familiar plant changes.  This month it is the turn of the Rhus genus, which has now been renamed Searsia.

 List of 40 species from the Mashonaland check list

Acacia amythethophylla; Acacia gerrardii; Acacia karroo; Acacia nigrescens; Acacia sieberiana; Albizia antunesiana; Albizia amara; Brachystegia boehmii; Brachystegia spiciformis; Celtis africana; Cussonia arborea; Diospyros lycioides; Diplorhynchus condylocarpon; Dodonaea viscosa subsp. angustifolia; Erythroxylum emarginatum; Euclea schimperi; Faurea rochetiana; Flacourtia indica; Grewia monticola; (Maytenus) Gymnosporia senegalensis; Julbernardia globiflora; Lannea discolor; Ochna schweinfurthiana; Ozoroa insignis (reticulata); Parinari curatellifolia; Pittosporum viridiflorum; Pleurostylia africana; Pseudolachnostylis maprouneifolia var. maprouneifolia; Psorospermum febrifugum; Rhoicissus tridentata; Searsia longipes (Rhus); Securidaca longipedunculata; Sterculia quinqueloba; Stereospermum kunthianum; Syzygium guineense subsp. afromontanum; Terminalia mollis; Uapaca kirkiana; Vernonia colorata; Zanha africana; Ziziphus mucronata.

Bernard Beekes

Combretum imberbe (leadwood). Photo: Burt Wursten. Source: Flora of ZimbabweCrotalaria pallidicaulis. Photo: Mark Hyde. Source: Flora of Zimbabwe