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Euphorbia aggregata Berger. (and E. pulvinata and E. ferox)


Rikus van Veldhuisen.

Introduction

euphorbia aggregata kommadagga
  E. aggregata Kommadagga
  euphorbia pulvinata steynsburg
  E. pulvinata, Steynsburg.
  euphorbia aggregata J&R94 Grahamstown
  E. aggregata, J&R94, north-west of Grahamstown.

Euphorbia aggregata belongs to a group of plants, together with the closely related species Euphorbia ferox and Euphorbia pulvinata, which can be recognised by their striking growing-shape. They exist mostly of compact, multiple branched and heavely thorned cushions. The english nickname "pincushion" says enough.
Farmers in South Africa are not very fond of these plants because they can injure their cattle badly. When an animal steps on one of these plants, the thorns can penetrate the hoof quite deep. The infections caused by this are very persistent and sometimes they even can cause death. Therefore the stock-farmers call these plants "voetangel", which means mantrap.

During our journey through South Africa in 1997, we found, during a short break, impressive large plants of Euphorbia pulvinata, just nearby the road. Although we had only little time to explore this locality, south of Aliwall North in the Elandspas, it was one of the highlights of our trip.
The giant cushions of many thousends little heads of just four to five centimeter in diameter were sometimes until three meters in height. A quick calculation informs us that such a plant must have 40.000 heads or more. I can only guess at their age, but no doubt they are very old.
Euphorbia pulvinata grows, in contrary to Euphorbia aggregata and Euphorbia ferox, preferably on stoney slopes, at the sunny northside of a hill of mountain.

Later this journey we stayed in Grahamstowm. We planned an excursion to find Euphorbia aggregata which grows, amongst others, in the surroundings of Carlisle Bridge, about 45 km north of Grahamstown. But we did not make it that far that day. We are used to stop quite often during our travelling, and on every of these stops we found something interesting. This took so much time that we didn't reach our destination. A part of what we found that day is described in the articles about Euphorbia polygona and Euphorbia inermis.
Now you might say that it's a bit silly to not accomplish the mission, but looking back now we are glad, because this was a good reason to try again. And so we did in 1999. This time with succes and we found Euphorbia aggregata at several localities. Luckely we again didn't find some of the species we were looking for also, so we have a good excuse to visit this wonderful country again.


Description

e. aggregata kommadagga
  E. aggregata Kommadaggaroad J&R 94
   
   

It is not known who discovered Euphorbia aggregata nor when. Mister Berger is the person who took notice of her presence in culture in 1902. At first he assumed it was the long lost Euphorbia enneagona of Haworth. In the end this identification did not satisfy and in 1907 he described these plants as a new species: Euphorbia aggregata.
Until today the identity of Euphorbia enneagona is still not clear. White, Dyer & Sloane presumed her to be identical with E. heptagona var. viridis, which they described themselves.
Euphorbia aggregata is a very variable species. The population west of Carlisle Bridge existed of about 150 plants, growing on approximately 1 hectare. Sometimes some plants grew together but between most of them was a distance of about 10 meters. Not two plants were similar.
The variety shows mostly in bodycolour, colour and length of the thorns, colour and size of the glands that surround the cyathia and the number of thornes per plant. Also there were plants with some crystate-shaping side-branches, closesly packed between the normal branches.
N.E. Brown described Euphorbia alternicolor, but White, Dyer & Sloane reduced this species to a variety: Euphorbia aggregata var. alternicolor. I don't think this is correct, because this description was based on a variegated individual and can therefore be a forma at most.
We found plants with a not plain green bodycolour between all three species: Euphorbia aggregata, Euphorbia pulvinata and Euphorbia ferox. We didn't find though the white-green stripes, as mentioned in the description of the variëteit alternicolor.


Distribution-area

The distribution-area of Euphorbia aggregata is north of Grahamstown, around Carlisle Bridge and from there to the north-west to Somerset East and futher to Graaff-Reinet.
In the south-east the plants have the most thorns. North of Graaff-Reinet the plants are greener and have less thorns. These show much resemblance with Euphorbia pulvinata.
White, Dyer & Sloane also mention Willowmore and Fauresmith as a habitat. Willomore lays in the middle of the distribution-area of E. ferox and Fauresmith lays in the Vrij Staat, inside the distribution-area of E. pulvinata. Therefore its more likely that these habitats are occupied by intermediate forms between the mentioned species.
We did't find any differences between the populations of the several localities which we visited at Carlisle Bridge and Somerset east. The populations existed of plants with a great variety, but comparable.

Euphorbia pulvinata

euphorbia pulvinata askeaton
  E. pulvinata Askeaton, growing on vertical cliffs. 
  e. pulvinata cathcart
  E. pulvinata Cathcart

Dr. Marloth has described Euphorbia pulvinata by the plants found by Dr. Galpin nearby Queenstown, two years after the description of Euphorbia aggregata. It's a remarkable fact that is took so long before these big and impressive plants attracted someones attention. These cushions they make are thus hard and solid you can just step on them without damage. That is to say: without damage to the plant, be sure to wear solid shoes!
Ephorbia pulvinata has, of the 3 named species, by far the largest area of distribution. It is located from the south at Queenstown, to the north, through and along Lesotho, the Drakensbergen, Free State and kwazulu Natal until in the Zoutpansbergen in the Northern Province.
The plants from the northern distribution-area differ clearly of those of the south. Marloth's intentention was to grant the nothern forms a different status. However he didn't push through, because, after an intensive studie, he came to the conclusion that none of the distinctive characteristics was constant. The differences though are considerable and to my modest opinion
the differences are greater as those between the southern form of Euphorbia pulvinata and Euphorbia aggregata.
The plants from the north distinct themselves by their leaves which have a length of no less than 3 cm, and by their ribs that exist of tubercles and which are larger in number and more narrow .There are more differences though. If you very interested you can study the literature named at the end of this article, you will find many pictures of both forms.

 

 

 

 


Euphorbia ferox

euphorbia ferox springbokvlakte
  E. ferox Springbokvlakte
  euphorbia ferox
  E. ferox, between Beaufort West and Aberdeen, or is it a ferocious spined E. mammillaris?

The third and last described species by Dr. Marloth in 1913 is Euphorbia ferox. She thanks her name to the fact that her thorning is the most heavy of the three species. And in contrary to the other two species she doesn't form a cushion, but she looks more like a closely-branched bush.
The distribution-area of Euphorbia ferox is located west of the one of Euphorbia aggregata. It starts in the east around Graaff Reinet and from there to the west until Beaufort West. More southern she is commonly found. At some locations her presence is even the most dominant vegetation, often growing together with Euphorbia esculenta.
On Springbokvlakte she often grows together with Euphorbia mammillaris. E mammillaris can be recognized by her longer and straighter and less thorned trunks. These trunks have ribs with little cross-channels. Because of that the trunks show a great resemblance with a corncob with thorns.
At several localities on Springbokvlakte, and also at Graaff Reinet, we found an Euphorbia with a different appearance, looking like a small Euphorbia ferox with lesser spination. These plants are also fairly widespread in cultivation. We think that a further investigation of these plants won't be a waste of time.
In "The Succulent Euphorbiaceae" by White, Dyer & Sloane we find a picture of a plant from the surroundings of Van Rhijnsdorp at the Knersvlakte. This plant shows a great resemblance with Euphorbia ferox. The Knersvlakte however is more than 500 km away from the distribution-area mentioned above. Unfortunately there is no other information about this finding. It does point out though that there is still a lot to explore in this immens land.

Subspecies or variety?

Recently G. Marx placed Euphorbia valida as a subspecies under Euphorbia meloformis and also Euphorbia symmetrica became a subspecies under Euphorbia obesa. These species are closely related and for an outsider its very difficult to distinguish them. There are differences though.
Perhaps the same can be done for the species under discussion here. Even better would be to place them as a variety instead of a subspecies because at many places intermediate populations can be found. A definite population consists of a collection of variable forms. The difference between populations is the frequency of the appearance in which these forms do occur. So can it be be that two individuals of two different populations look very similar and also, two plants of the same population can look very different. However when you are looking at the whole population, you can see the difference of the population with another one. When these mixed populations do appear also in the two forms of Euphorbia pulvinata in the North and with the lesser spined form of Euphorbia ferox in the East, then these two can be added to the complex, in my view best as varieties. Euphorbia aggregata with its several varieties would thus give a better reflection of the situation in nature.


Cultivation

Euphorbia Pulvinata is, like mentioned before, a plant that grows on hills. With a little imagination she even could be called an alpine-plant. Another reason for this is that she sometimes grows in areas with a lot of rain, up to 1000 mm per year, and even with snow sometimes. Herefor she can be very easily grown in culture.
This also applies to the other species, though less. They do need a lot of light though to keep their compact growth-form. I myself grow especially E. Pulvinata in summer outside and until now that gets me very beautiful plants. In winter however some plants started to rot a little, perhaps I should keep them outside also in winter, who can tell?
It just remains a fact that a beautiful compact plant of these species provide us with a magnificent view, unfortunately these plants ara seldom found in our collections.

Literature:

White, A., Dyer, R. A., Sloane, B. L., (1941), The Succulent Euphorbiceae (Southern Africa) 2 Vols.
Fourie, S. P., An Introduction to the Succulent Euphorbias of the Transvaal, part 3, The Euphorbia Journal, Vol. 6, p. 113 - p– 125.
Hargreaves, B. J., The Other Spurges of Lesotho, The Euphorbia Journal, Volume 8, p. 126 – p. 132.
Marx, G., The Succulent Euphorbias of the Southeastern Cape Province, The Euphorbia Journal, Volume 8, p. 74 – p. 102, part 1.


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