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This is actually rather a difficult selection to make. It is not as straightforward as it might seem to say just how 'big' an individual tree is. The height is not the only criterion; some kinds of tree are very tall and slender, but by contrast, others are not very tall, but grow enormously thick. In addition, others have canopies that spread very wide, and have a very heavy mass of leaves. In judging 'bigness', factors like height, canopy spread, trunk girth, and overall mass must all be taken into consideration.
It is also the case that, in any tree species, we do not always know just how big individuals of that species can become. This is especially true of rare species. With the sneezewood (Ptaeroxylon obliquum), for example, most individual specimens are average-sized, about ten metres in height, but occasionally there will be an individual that is much, much bigger. In South Africa this happens frequently; most of the country is semi-desert or dry savannah, with infrequent rainfall, lots of browsing mammals, and frequent fires, and the trees growing in this habitat are relatively stunted. Trees from the same species can grow very much bigger when they get more water, and are protected against fires and browsers, so we cannot always say how big a species might grow. A tree guide might state that a species grows to a height of five to ten metres, because botanists have observed that pretty nearly all mature individuals of the species fall within this range, but in some remote canyon somewhere, where no botanist has yet been, there may be an individual that is 20 or 30 metres tall. There are indeed specimens of some species in remote locations that are well beyond the limits stated in botanical guides.
On the other hand, there is also the factor of exaggeration; it's difficult to know just whose figures to trust. Many people are not very good at observing and estimating factors such as height and girth. They will look at a tree and say it is 30 or 40 metres tall, when in truth, its height is only about ten metres. A truly big tree is so impressive and imposing, that people who see it might want to believe that it is much bigger than it actually is. Even a writer of reputation such as Eugène Marais has fallen into the temptation of ridiculously exaggerating the size of trees, so as to claim that the biggest trees in the world belonged to South Africa. The true height of a tree can usually only be accurately determined by rigorous measurement, using trigonometric techniques. Similarly, the trunk girth or circumference needs to be measured to be valid. It should be measured at breast height, or about 1.3 - 1.5 metres from the ground. Any non-rigorous claims for tree size have to be disregarded.
In general, South African native trees are relatively small. Much of the country consists of desert, succulent or shrubby semi-desert, and almost treeless grassland. The rest consists mostly of savannah, with small trees dotted here and there amidst the grass, and most of the trees here are less than five metres tall. Some areas of 'dwarf savannah' have miniature trees less than two metres tall, but this is largely due to factors such as excessive browsing by domestic goats and the removal by humans of large trees for firewood, not to mention bush fires. In more protected areas, savannah trees can reach and exceed 20 metres in height – especially if they are growing on the banks of rivers. In forests, the tree canopy can be 10-20 metres in height, with some individual trees exceeding this. All in all, a South African tree can be considered 'tall' if it exceeds 20 metres.
In terms of thickness, a tree can be considered very thick if it has a trunk approaching or exceeding 1.8 metres (six feet) in diameter. A tree of this thickness will need at least three large men to encircle it, with their arms spread as wide as possible and their fingers just touching.
Bearing in mind these constraints and the unavoidable subjectivity involved, here's a list of the ten biggest tree species of South Africa1.
1. The Baobab, Adansonia Digitata
This tree is in first place because of its potential for overall mass: girth, spread and height combined. The baobab never becomes very tall, seldom exceeding 20 metres in height, but it can become extremely fat with a massive trunk and branches. The biggest baobab in South Africa is only 22 metres in height, but has a trunk that is 10.47 metres in diameter. It has a crown that is 38.2 metres in width. It is therefore almost twice as broad as it is tall! There is another baobab that is shorter, being only 17 metres in height, but having a trunk an incredible 15.9 metres thick! Its crown spreads to 37 metres in width. There are many other individual baobabs that approach or exceed 10 metres in trunk thickness.
These trees have the greatest potential for hugeness if allowed to live very long, but how long can they live? In 2007, the biggest baobab in South Africa was officially determined to be about 2,000 years old, and many others may exceed 1,000 years. Baobab wood is very soft and doesn't form growth rings, so the age needs to be determined by taking carbon-14 readings.
The baobab grows in warm, dry savannah regions, mainly in the far north of South Africa (and up into the drier parts of tropical Africa), where it is by far the biggest tree. Other trees growing alongside it are mopane (Colophospermum mopane), blue hook thorn (Acacia erubescens), white syringa (Kirkia acuminata), sjambok pod (Cassia abbreviata), sesame bush (Sesamothamnus lugardii), and several species of corkwood (Commiphora).
2. The Outeniqua Yellowwood, Podocarpus Falcatus
This tree can become very tall, and also develops quite a thick trunk and a broad, deep, dense crown. In terms of massiveness, these can be very imposing, but it's difficult to say just how big the tree can become. So many of them have been cut down, having excellent wood, but in the old days, when they cut them down, they didn't always measure them accurately. It is said that there used to be trees of up to 60 metres in height, yet today, the biggest known specimens are less than 40 metres tall. Even so, these individuals are incredibly impressive. In terms of overall mass, they must come fairly close to the huge baobabs, because of their huge and dense crowns. The wood is also much denser and heavier than that of the baobab. The two biggest Outeniqua yellowwoods currently recognised in South Africa are 39 and 36 metres tall, with trunks 2.22 and 1.88 metres thick, and crown diameters of 29.6 metres and 33.6 metres across, respectively.
Because of the excellence of its timber, many of the largest Outeniqua yellowwoods have been cut down. There may be specimens bigger than these 'official' champions in some remote ravines, where woodcutters haven't yet been able to get to them. Their inaccessibility will also have made these difficult for botanists to discover, too.
The Outeniqua yellowwood is in second place for the reasons of both its actual and potential size.
3. The Common Cluster Fig, Ficus Sycomorus
This tree can become amazingly huge. Its trunk doesn't grow very tall and straight, but spreads outwards into a vast dense crown of long, sturdy branches. At the bottom, it spreads out into huge flaring buttress roots, often snaking out over the ground for many metres from the central trunk. These trees mostly grow along rivers in warm savannah regions; many superb specimens can be seen along the Limpopo and Pafuri rivers. The champion common cluster fig grows near Polokwane/Pietersburg, and stands 25 metres tall, with a trunk 3.9 metres thick and a crown spreading to an incredible 45.7 metres in width. There are many other specimens exceeding 20 metres in height and 30 metres in crown width.
The cluster fig is also made impressively conspicuous by its yellowish to yellow-green bark. This is similar to that of the fever tree (Acacia xhanthophloea), that also grows along tropical and subtropical rivers. The cluster fig is a favourite of animals and birds, bearing its large figs in generous quantities pretty much throughout the year. These fig trees are always bustling with noise and activity.
4. The Matumi, Breonadia Salicina
This tree usually develops a massive tall and straight trunk. It makes excellent timber – heavy, hard and fine-grained – and again, many of the really big specimens have been cut down. The biggest one remaining is 41 metres tall, with a trunk 2.44 metres thick. Its crown spreads to 32.3 metres in width. There are many others still standing which approach or exceed 40 metres. They grow in warm, moist forests as well as on subtropical riverbanks.
The Matumi is more of an upright, straight and narrow kind of tree. This shape is enhanced by its long, narrow lancehead-shaped leaves that usually hang downwards. Despite the comparative narrowness of its crown, it counts as a 'big tree' because of the volume of its trunk, which rises almost to the top without any significant narrowing.
5. The Wonderboom Fig, Ficus Salicifolia
This one makes the list because of a freak individual. This ancient tree stands in the city of Pretoria and a whole suburb is named after it. Even long ago, this was a big tree with very long branches. Some of the branches eventually drooped under their own weight and reached the ground. There, these branches sprouted roots (many of the wild fig trees can easily produce new roots on their trunks and branches) and became new 'trunks', supporting new branches that spread out and drooped and rooted even further away. So, a large group of 'secondary' trunks have grown around the central trunk. Eventually, the central trunk died, leaving the secondary trunks seemingly disconnected, however they are all part of a single 'complex' individual. This 'complex' is currently 22 metres tall and 53.3 metres wide, and in terms of total mass might rival even the huge baobabs.
No other individual of this species comes close to the original Wonderboom, or 'wonder tree', but the existence of this one individual shows that the species does indeed have the potential for greatness. Under optimal circumstances even single trees of this species can exceed 20 metres in height and spread, and have a trunk over two metres thick.
6. The Monkey Thorn, Acacia Galpinii
These beautiful thorn trees line the banks of many of the larger rivers in the far north of South Africa. They qualify as huge in height, thickness, and canopy spread. The largest recorded individual stands 30 metres tall, with a trunk three metres thick and a canopy spreading to 35.1 metres.
This thorn tree species is quite common, and there are many outstanding specimens still standing in the wild. Sadly, some of the best ones are due to be submerged beneath a new artificial lake in Sekukuniland, but the species itself is in no danger. A very large number of trees have been planted along streets and in gardens, where they grow fast, and rapidly become very big. In fact, this is rather a concern: this tree grows so strongly that it can endanger the nearby roads and buildings.
7. The Ana Tree, Faidherbia Albida
This species is related to the thorn trees; it too grows along rivers in the north of South Africa. The biggest known living specimen stands 36 metres tall, with a trunk 1.78 metres thick and a crown 36.2 metres wide. This is the species that was so ridiculously exaggerated by Eugène Marais. About a century ago, he made the claim that he measured trees as being over 60 metres in above-ground height with an additional 60 metres of trunk submerged beneath drift-sand piled up over many years by the river, giving a total height of 120 metres! The trees for which he made this claim have long since disappeared, and, based on trees measured recently, his claims would appear to be exceedingly unlikely. Nevertheless, living Ana trees are still among the largest in the country.
Ana trees are rapid-growing under optimal conditions - deep soil with good drainage, a hot climate, and moderate water. They initially grow rapidly tall, staying rather narrow, but later in life the trunk starts to thicken and the canopy starts to spread. They can probably live for a few centuries; there are some Ana trees in the Potgietersrus/Mokopane area under which David Livingstone is said to have rested.
8. The Red Stinkwood, Prunus Africana
This species occurs in forests, and, since less than 1% of South Africa is forested, it is rather rare. The bark smells of bitter almonds when newly crushed, and it has medicinal uses now recognised by the international pharmaceutical industry. When left alone, this tree can become very tall: the biggest specimen stands 40 metres tall with a trunk 1.83 metres thick.
The red stinkwood is in the same genus as the well-known peach (Prunus persica) and cherry (Prunus avium, P. cerasus) trees of more northern climes. The 'African' Prunus is widespread in the forests of tropical Africa, and also occurs in Madagascar.
9. The White Stinkwood, Celtis Africana
The champion white stinkwood is stated as standing at 39 metres tall, with a spread of 19.7 metres and a trunk girth of 5.05 metres. This would make this individual one of the thickest trees in the country, freak baobab specimens excepted. In general, individuals range from small to medium-sized trees in savannah and thicket, to giants growing in moist ravine forests.
White stinkwoods are very beautiful trees. Under optimal conditions - deep, fertile soil, lots of water in summer, and mild to warm temperatures - they grow fast. Many of them are planted in cities and gardens in South Africa. They are somewhat less aggressive growers than most of the other big trees in this list, and are less likely to pose a danger to roads and buildings.
10. The Sneezewood, Ptaeroxylon Obliquum
This species is widespread in South Africa, occurring in a variety of different habitats, from dry open woodland and savannah to moist forests. In dry areas they rarely exceed 10 metres in height, but in forests they can become huge. A sneezewood growing in the Lekgalameetse Nature Reserve in the Limpopo Province holds the record for being the tallest indigenous South African tree: it stands 45 metres tall, with a rather slender trunk girth of 1.29 metres and a crown 22.7 metres wide.
The sneezewood is another very attractive tree species that does well in suburban gardens and city parks. It can tolerate much drought, but also takes advantage of good watering. It has attractively-divided bluish-green leaves and a 'spicy’ smell that can be noticed from quite a distance.
Apart from those mentioned here, there are many other South African species that can also become very big; after all, there are over 1,000 tree species growing there. Many of them are very poorly known or very rare, with most individuals growing under harsh conditions. It would be a worthwhile project to try and plant many individuals of as many South African native tree species as possible, in a large number of different places and conditions, so as to discover the optimal habitat for each species. Then, planting large numbers under these optimal conditions, and taking excellent care of them for as long as necessary, would prove how big they really can become. Such a project might significantly improve an understanding of the potential size of South African trees, not to mention helping with the conservation of the superlative botanic diversity of the country.
Compared with other countries, South Africa cannot claim to have the biggest or the most impressive trees in the world. The only one that stands out internationally is the baobab. Under optimal conditions and given enough time, these can certainly become some of the thickest trees in the world, but that species is shared with many other African countries, and there are some great baobabs in Madagascar as well. As for height, the sneezewood (mentioned above) is the tallest known indigenous tree in South Africa, but at only 45 metres, this cannot rival the tallest trees in the world: the coast redwoods (Sequoia sempervirens) of the western coast of North America; the douglas fir (Pseudutsuga menziesii), also of the western regions of the USA and Canada; and the mountain ash (Eucalyptus regnans), of Australia. These species can all exceed 100 metres in height, and could possibly reach even 120-140 metres. The most massive trees in the world are the giant sequoias (Sequoiadendron giganteum) of California, some species being over 80 metres tall, while also having trunks over seven metres thick. The banyan figs (Ficus bengalensis) of Asia might also be champions in overall mass. This is another kind of 'compound' tree similar to South Africa's Wonderboom, except that the Asian species can develop hundreds of subsidiary trunks from roots dropping down from the branches. The largest known individual has over a thousand trunks and its canopy spreads over about 1.6 hectares, making it more than 100 metres in width!
So, South Africa's trees are nowhere near record-breakers. But her biggest trees are still her biggest trees, and should be cherished for what they are!
Wherever you are in the world, dear Reader, learn about your country's native plants, and be proud of them!