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Euphorbia susannae Marloth

Rikus van Veldhuisen


Introduction

euphorbia susannae
 
Full grown plant. At the right there me be a seedling.Western locality

One of the most beautiful and most characteristic species of the genus Euphorbia is undoubtedly Euphorbia susannae. She appaers only at a few minor places of finding in the Kleine Karroo. At some known localities she can no longer or almost not be found. This is most likely caused by the collecting of plants by "plant-lovers"
The last years in succulent-literature Euphorbia susannae got frequent attention. Your writer thinks though to be able to add some things worth knowing to the already existing knowledge.

Discovery

Euphorbia susannae was discovered in 1925 by Dr. John Muir and was described 4 years later by Dr. Marloth. She was named after Dr. Muir 's wife: Susanna. By the way, this woman's name was acoording to some writers Suzanna, with a z, and named our plant Euphorbia suzannae. I however use the way of writing as White, Dyer and Sloan do.
Dr. John Muir for that matter got more acquaintance through the mesemgenus Muiria. This genus has only one species: Muiria hortenseae. Hortense was John and Susanna's daughter.

Where can Euphorbia susannae be found?

Euphorbia susannae grows only at some locations in the Kleine Karroo not far apart. The Kleine Karroo is one of the most beautiful succulent-areas in the world with many remarkeble species which don't grow anywhere else. Haworthia's and Euphorbia's but especially many species of Mesems come from this dry area which begins in the west at Worcester and ends in the east at Oudtshoorn. The most known places in the Kleine Karroo are Ladismith and Calitzdorp. The area gets no more as 150 mm rain in a year and is in the rainshadow of some mountain chains. In the south these are the Langebergen and at the northside are the Klein – and Groot Swartberge. The various mountain passes are breathtaking beautiful and a high point for every visit to this region.

euphorbia susannae
  The bigger form with bright green colour. Northeast of Riversdale
  euphorbia susannae, atypical
  A-typical, above the ground. Eastern locality
  euphorbia susannae, western locality
  Completely withdrawn in the ground. Very stoney soil. Western locality
  euphorbia susannae in the shade
  Young plant in the shade of a bush. Western locality
  E. susannae, eastern locality
  A young plant with purple coloured tips of the tubercles caused by the sun. Eastern locality
  e. species nova j&R 200
  E. species nova J&R 260, completely above the ground. Noth of Barrydale
  e. species nova, in full sun
  Idem, in the ful sun the growth is much more compact
  e. species nova
  Idem, she branches above the ground
  e. susannae in full sun
  E. susannae in the full sun, in a pebble-area. Eastern locality
  gibbaeum album
  Gibbaeum album
  muira hortensia
  The "mouse-heads" of Muira hortensia
  muira hortensia
  The "mouse-heads" of Muira hortensia

The finding of Euphorbia susannae

On our trip in 1999 we sought for Euphorbia susannae in vain. Two years later we were more succesfull. In several publications about Euphorbia susannae we read about how difficult it is to find this species in nature. Your writer however was only two steps out of the car when he sighted the first plant. The plants stood mostly in full sunlight. They attracted attention by their bright green colour and some of them were more then 30 cm in diameter.

This first place was the most eastern locality where we found Euphorbia susannae. This population existed of more than 200 plants. They were very healthy and there were older and big plants with many heads as well as seedlings of only a few centimeters. It was striking that the older bigger plants had two different growth types. Normally she grows completely withdrawn inside the ground with only the tips of the trunks above the ground. At this place however plants grew totally above the ground and were shaped like a half-sphere or a cushion. This way of growing was much more similar to way they grow in culture.

White, Dyer and Sloane describe the thickness of the trunks of this species to be 2,5 to 3,5 cm.
At this finding-place however the trunks grew to a thickness of no less then 7 centimeters. Futhermore these plants were bigger and stronger in all their measurements as described in White, Dyer and Sloane.

A second place of finding, only a few kilometers further to the west, appeared to be in the verge of a dirtroad. Here were less plants, estimated around fourty. Here also we found a nice number of seedlings so it seems that this population is able to maintain itself, in spite of the fact that it was easy accessible. All plants at this locality grew withdrawn in the soil and these plants were much smaller.

Deviating species?

Much further to the east, a bit north of Barrydale, we found a population of Euphorbia's that showed clear differences wit E. susannae. Where Euphorbia susannae has 12 tot 16 ribs per trunk, this new shape had 6 to 8 ribs per trunk. Almost all plants grew completely in the shade underneath little bushes. Above that the trunks grew completely above ground en were more than 25 cm long. The plants had mostly a dirty brown/green colour. Only the ones in the sun were dark brown/red. Remarkeble was the fact that the ribs, just like those of E. susannae, had clearly visible tubercles of which the tip was curved back downwards. This population existed of approximately 50 plants and showed within this population little variaton.

These deviating plants showed a superficial resemblance with Euphorbia pseudoglobosa, the closest related species of E. susannae. However Euphorbia pseudoglobosa misses the clearly curved back tubercles. Unfortunately we didn't find any flowering plants or plants with fruits or seedlings. Some unique aspects of E. susannae are the striking colour of their fruits: dark-purple and the hair-shaped leave-remains on the tubercles of seedlings. Futhermore the tubercles of seedlings are more thinner en longer as those of adult plants and seem therefore almost hairy.

Futher investigation of this new form off especially the flowers, fruits and seedlings will have to point out the taxonomic state of these plants. The obvious differences with the mentioned species and the little variation inside the population seem to point out to the rank of a independent species.

By the way it remains to be seen if this population is this new. White, Dyer and Sloane mention in their description of Euphorbia tubiglans a deviating form found by Dr. J Luckhoff in the surroundings of Barrydale. This form had 7 to 8 ribs in stead of the 5 ribs per trunk what is typical for Euphorbia tubiglans.
However E. tubiglans is also related to E. pseudoglobosa an E. susannae, she has a closer relation to Euphorbia juglans en Euhorbia jansenvillensis.
Possibly did neither White, Sloane or Dyer see this these plants in the flesh. At that time all these plants were only recently become known which makes its much more difficult (because of ignorance) to put these plants in a proper relation.

The Kleine Karroo

The soil of the Kleine Karroo is very sandy. At some places layers of stony ground, often white quartz, come to the surface. These places are often a few hundred of square meters in size, but sometimes just a few square meters. They draw attention by the deviating white colour and the more or less lacking of bushy-like vegetation. If these places are located on or near a top of a low hill, no matter how small the places are, they will be often real "hotspots" for succelent plants. Many species grow only at these pebble-spots and often characterize themselves by dwarf-growth.

Euphorbia susannae also grows at or closely nearby suchlike pebble-areas.But also other jewels of plants appeared to grow here, like the spherical Crassula columnaris, Haworthia arachnoïdea var nigricans, Adromischus filicaulis ssp marlothii and Pelargonium laxum, just to mention a few.
At other similar places nearby we found Gasteria brachyphylla, Quaqua ramosa, Conophytum spec., multiple species of Gibbaeum and the already mentioned Muiria hortenseae. Especially the finding of Gibbaeum album in full blossom wan an unforgetable experience. Dark-violet flowers contrasted beautifully with a almost white plantbody. Although some plants in this population had white flowers.

What's in a name?

Various species of the genus Gibbauem are designated in the South African language by 'Haaibekkie'. In English this means 'beak of a shark'. This very suitable name is based on the shape of the two leaves that form together the whole sprout. They differ in size and because these leaves stand closely together the in-between cleft of the most species lookes exactly like the beak of a shark, though without the teeth of course.
Gibbaeum album herself has also a South-African name: Bababoutjie, what means 'babybuttock'. And there's the local name for Muiria hortensia: Muiskopvygie, 'vygie' means 'mesem', and 'muiskop' is 'mouse-head'. And indeed this plant looks much like a little mouse-head.
So we get back to Euphorbia susunnae, her African name is Knoppiesnoors. 'Noors' is the common name for a spurge and 'knoppies' is something like 'little buttons'.

Cultivation

Euphorbia susannae can be cultivated reasonably well, though she sure has a mind of her own. Often the loss of this plant can be blamed on the use of soil that doesn't permit the water pass trough enough. Another reason can be a standing-place in the full sun without a good ventilation She prefers a place in a greenhouse with lots of light without being in the full sun to much.
In cultivation she will be less or not at all withdrawn in the ground, like she does most often in nature. We don't have the extreme temperatures or dryness in our greenhouses that makes that nessecary
Besides this she will branch more what makes elder plants grow in a pillow-shaped form.
The multiplying of this species can be done by either sowing or cutting. Moreover a cutting will grow into a typical plant which can not be distinguished from a seedling when it gets older.

Cristates

Striking is the rather big tendency of Euphorbia Susannae to form cristates. Sometimes these cristates are completely or almost completely without chlorofyl . These plants can only be multiplyed by cutting. To people that are fond of cristates they can be a welcome addition to their collection.


And so this essay about this very attractive species coming from a very interesting area comes to it's end. I hope that your interest for Euphorbia susannae has been awakend and that if you ever encounter this little plant at a fair or a nursery you will feel a bit different about this little dwarf.

Literature:

Grantham, Keith, Home and away, (2000), Euphorbia Studygroup Bulletin, Vol. 13, No. 3.
Hewitt, T. M., Euphorbia suzannae Marloth, (1978), K. u. a. S., No. 3.
Jaarsveld, Ernst van, Wyk, Ben-Erik van, and Smith, Gideon, Succulents of South Africa, (2000), A guide to the regional       diversity.
White, A., Dyer, R. A., Sloane, B. L., (1941), The Succulent Euphorbiae (Southern Africa), 2 Vols.
Zimmermann, Dr. Norbert F. A., Notes on succulent Euphorbias of the little Karoo, (1996), Euphorbia Studygroup Bulletin,
Vol. 9, No. 2.

 



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