IAP clearing activities reveal many of the Endangered Dahlgrenodendron natalense (Sandstone quince; sandsteenkweper)
Text by: K. Grieve, W. Neale and R. Crous
Photos by G. Nichols and G. Grieve
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| Dahlgrenodendron natalense |
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| Fruits of Dahlgrenodendron natalense (G. Nichols) |
Extract from an information board mounted at two of the readily accessible specimens of Dahlgrenodendron natalense at Umdoni Park.
About 20 years ago the Trustees of Umdoni Park asked the Wildlife and Environment
Society of South Africa (WESSA) to name and tag the trees around the Trustees’
cottage and along the back road through the forest at Umdoni Park. A group of four tree “fundi’s” : Eugene Moll,
Hugh Nicholson, Trevor Coleman and Keith Cooper, set about recording the trees that
required tree tags. Amongst the four of
them, there were few, if any, indigenous trees in Natal unknown to at least one
of them.
Imagine the
surprise then, when along the forest road, a fairly large tree was encountered
that none of the four could identify. It
was totally unknown, even the genus was a mystery. The Natal and National
herbaria required fertile material (flowers and/or fruits or better still, both)
before a name could be given. Hugh
Nicholson (now deceased) eventually found fertile material on the Umdoni Park
mystery tree. Natal herbarium had no
idea what it was and so sent the specimens to the National Herbarium in Pretoria. They too had no idea and sent the material to
Kew herbarium in London (the world HQ for botanical nomenclature). After
several months Kew came back with the great news. It was a new genus for South Africa and a species new to science. They gave it the
name Beilschmiedia natalensis.
What a find!
Shortly after this discovery, a few more specimens of Beilschmiedia natalensis were found on the Natal South Coast and at Krantzkloof Nature Reserve on the Nqutu river. Several years later, Prof. Braam van Wyk of Pretoria University and a great friend of the late Hugh Nicholson, wanted to see all the B. natalensis trees in Natal. He took core samples of the wood and bark and had these compared with samples of Beilschmiedia from other parts of the world (DNA tests etc). They did not match so he re-described our Umdoni Park B. natalensis and gave it a completely new genus that he called Dahlgrenodendron natalense. So our famous Umdoni Park tree was not just a species new to science but a new genus too.
Some years later when Roy Broderick
was working on alien plant eradication at Umdoni Park, he phoned me to say he
had found quite a few more D. natalense off the main block of the
forest going down to the stream. I immediately went down to see them and
sure enough, there were a good few additional trees in the forest. The Umdoni Park subpopulation of D. natalense is, as far as we know, the largest of this tree in the world.
Originally described in 1973 by Ross as Beilschmiedia natalensis in the family Lauraceae, in 1988 the species was renamed in a new genus as Dahlgrenodendron natalense by Van der Merwe, Van Wyk and de Kok. Dahlgrenodendron acknowledges Swedish botanist R.M.T.Dahlgren (1932-1987); dendron = tree; natalense = from Natal, now KZN.
The new genus was based on several characters including its pollen structure, which was unknown in the Lauraceae. Other distinguishing features are that it has opposite versus alternate leaves and in Beilschmiedia the flower is completely deciduous whereas in the Sandstone Quince the base of the flower enlarges to envelope the fruit. In 1990, Kostermans, a botanist based in Indonesia and an expert in the Lauraceae, suggested that the different pollen morphology was insufficient to justify a new genus and placed the species in Cryptocarya as C. natalensis instead. While this nomenclature has been followed by Kew’s Plants on the World Online and iNaturalist, SANBI has retained the name Dahlgrenodendron natalense. SANBI’s approach seems sensible given that Kostermans acknowledged that the tree seemed intermediate between Cryptocarya and the genus Aspidostemon of Madagascar, suggesting more work was needed to confirm its placement.
The type specimen of this species was
collected at Umdoni Park in 1971 by Hugh Nicholson. A type specimen is the
original collection of specimen material against which all further specimens
are compared.
Dahlgrenodendron natalense is regarded as a rare tree (EN), up to 20 m tall, that grows in scarp forests, forest margins and near streams. It is known mainly from Pondoland, between the Msikaba River and Port Edward and there are also one or two at Umdoni Park (as it was thought at the time), Kranzkloof Nature Reserve and Ongoye (possible extinct there).
Until recently it was
thought that the trees did not reproduce well, probably because of limited fruit
set or parasitism. It was previously estimated that the total
number of individuals did not exceed 200, and it was considered to be an
ancient relict on the brink of natural extinction (Van der Merwe, et al. 1988).
For many years there were only two known mature Dahlgrenodendron natalense trees at Umdoni Park. Very few fruits were seen and it appeared that there was no natural recruitment. The future of the trees seemed uncertain.
However, all this changed when Wendy Neale was contracted to eradicate invasive alien plant species at Umdoni Park, these efforts fully supported by the estate Manager, Rynhardt Crous. In the process of clearing plants from the forest (Pereskia aculeata in particular), she came across a few trees that she thought might be Dahlgrenodendron. Their identity was subsequently confirmed by Elsa Pooley and Geoff Nichols. Further clearing down the forested slope to the Mkumbane River has revealed the presence of approximately 130 trees, with the expectation of more to come.
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| A cluster of coppiced trunks of Dahlgrenodebdron natalense after the surrounding Pereskia aculeata was cleared |
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| Large basal trunk of a Dahlgrenodendron natalense with several coppice shoots |
Excited by this discovery and the
realisation that the trees were reproducing, Wendy decided to propagate seeds
herself. The attempt with the first fruit was a non-starter as the seed had
been eaten by a caterpillar. The
caterpillar has tentatively been identified as the larva of one of the Crambid Snout
Moth species but more larvae will have to be reared to confirm this.
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| One of the seedlings of Dahlgrenodendron natalense |
With guidance from Geoff Nichols, Wendy started with one fruit. She cleaned the leathery covering and flesh from the seed and planted it in July 2021. After three months, a shoot appeared and by November the shoot was approximately 20 cm tall. As she collected more fruits, she continued to propagate the seeds. The plants are slow growing but do well in pots until they are ready to be planted out in the part of the forest where the fruits were found. Wendy’s efforts have been so successful that she has returned three trees to the forest and has 30 growing in pots. This achievement contributes greatly to current knowledge about Dahlgrenodendron natalense and provides important information for the dendrological community.
References:
Boon, R. 2010. Pooley’s Trees of Eastern
South Africa: A Complete Guide. Flora and Fauna Publications Trust, Durban.
Kostermans, A.J.G.H. 1990 Botanica Helvetica 100(1): 36.
van der Merwe, J.M., van Wyk, A.E., Kok, P.D.F. 1988. Dahlgrenodendron, a remarkable new genus of Lauraceae from Natal and Pondoland. South African Journal of Botany 54(1): 80 – 88.
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