Euphorbia subgenus Euphorbia section tricanthium Jacobsen. Part 2
Rikus van Veldhuisen
Euphorbia xylacantha Pax.
In literature Euphorbia xylacantha is not frequently encountered, though in nature she grows fairly common in Northern Somalia. Susan Carter (1992) writes that this species, even at the specialized growers, is rarely seen. Nowadays this beautiful species is more widely available for the interested collector.
As said before this species is also described by Pax in 1904. She quickly fell into oblivion after N. E. Brown (1911-1912) sank her into synonomy under the herefor dealt with Euphorbia monacantha. S. Carter (1992) however reinstated E. xylacantha as a species of its own on bases of different habit and different natural habitat. The habit shortly can be described as follows; a strong mainsprout can grow as high as 20 centimeter, with lateral branchus up to 40 centimeter long. The whole plant can reach a diameter of 50 centimeter.
Plants in cultivation can be extremely variable. I grow plants in my collection with a very weak developed mainstem and lateral branches reaching 40 centimeter in length and 2 centimeter thick under the name E. xylacantha. The only added locality data is Somalia. This less specialized plants, which shows a lot of similarity with E. triaculeata and may well be this species, are right next to plants with a strongly developed mainstem, short thin lateral branches and fiercely spined. These last mentioned plants stand alone in their most remarkeable feature of having a very light grey-green bodycolour marked with a bright grey pattern. Susan Carter (1992) recognized variation in this species in nature stating that bigger, more robust plants do grow in the north-eastern part of Somalia and the smaller, less robust plants grow in the north-western Bari Region. No mention is made about variation of the size of the mainstem or its striking bodycolour.
Euphorbia xylacantha is a valuable addition to our collection and does not present the grower to much difficulties in its cultivation. Sowing this species is fairly easy and in a year or two one has nice plants. The two-times-cutting methods worked very poorly for me and did never resulted in a plant with a strong developed mainstem.
Euphorbia immersa Bally and Carter.
For more than than half a centurie there are no new species described in this group, untill P. R. O. Bally and S. Carter in 1967 describe Euphorbia immersa in in the journal Candollea. In the very same article also the untill then virtually unknown E. turbiniformis is brought into daylight, for sure one of the most appealing species of Euphorbia of all.
Of all the species dealt with here, the habitus of Euphorbia immersa superficially looks most like the medusoid species from South Africa.
The mainsprout is very short and erects from a beetlike tuberous root, on which numerous, weakly spimed, lateral branches are placed. However there are substantial differences between Euphorbia immersa and E. xylacantha, Susan Carter (1992) writes that intermedeate forms appear in the neighbourhood of Hargeisa and that therefor further fieldresearch is needed.
In cultivation this species is characterized by it willingness to flower, several shifts during a growthseason and nearly always there seem to be some yellowbrown cyathia on an adult plant. Furthermore Euphorbia immersa is, like most of the species in this group, a selffertile species. Fertization however seem to be erratic. More than once pollinating her with a soft brush was fruitless and having done nothing at all many fruits appeared. Nevertheless fertile seeds are little in number after selfpollination. Of all species in this group the seedlings of Euphorbia immersa are the most difficult to keep alive during the first months of their life. Once the plants are bigger they do not represent any difficulty in cultivation. Lateral branches taken as a cutting are rooted fairly easily and do form sideshoots which behave like a mainsprout. These sideshoots can be taken again as a cutting and so original growing plants are fairly easy obtained.
In one the very few times Euphorbia immersa occurs in literature it is made mention of the use of its latex as a chewing gum. This rare use of a Euphorbia by the local youth is as follows; a stick is pointed in the centre of a plant. The non-irritating latex running freely is glued to the stick and after coagulating it is being chewed on. I personally would not recomment this use to your plants, because Euphorbia immersa is for its dwarf- and special habitus, one the the most desireable and rarest of all Euphorbias.
Euphorbia actinoclada S. Carter.
For sure Euphorbia actinoclada is one the most frequently encountered species from this group of species in cultivation, which is not in the last place caused by its relatively ease of cultivation. This species is together with Euphorbia kalisana and 23 other species of East African Euphorbias deribed in 1982 by Susan Carter in Hooker’s Icones Plantarum. Before publication Euphorbia actinoclada was widely available to the collector of succulent Euphorbias under various names, such as Euphorbia species nova, E. species affinis monacantha or E. monacantha. Even today one can find designed as such.
Euphorbia actinoclade formes a well developed mainstem, usually not higher than 5 centimeter, with lateral branches up to 15 centimeter long. In cultivation these sidebranches do tend to grow much longer, due to too less light, to much nutrition and water and which does not add to its attractiveness. The colour of the cyathia and its glands is not mentioned in this description, but in cultivation one can see flowers in most various colourscemes. From green to yellow and from brown to red in nuances in between them do occur and as a bonus, the cyathia do appear in vast numbers at the flowering time. Most of the time two flowering periods do occur, one at the beginning of the growing season in spring and one after the height of summer.
In its original diagnosis by Susan Carter (1982) the colour of the plantbody is mentioned though as ‘dark green, rather than glaucous’. Strikingly these glaucous, covered with a blueish haze, plants are most frequently seen in cultivation. Such plants are known to originate from Negele, Ethiopia and are further characterized by a weakly developed mainsprout and brown-olivegreen with dark red cyathia. Plants with a yellow green bodycolour are also quite common, but are mostly labelled as Euphorbia monacantha or E. species affinis monacantha. Plants with the dark green body colour are rarely seen in cultivation.
The typelocality of Euphorbia actinoclada is Dandu, Northern Frontier Province in Kenya. Mike Gilbert mentiones in his Flora (1995) two different forms from Ethiopia. One is originating southeast of Aware and is differring in having much taller (up to 15 centimeter) main stem and in having brown cyathia. This plants grow into an untidy bush, because the lateral branches grow fairly long and do have the habit of re-branching as well. The other one from east of Sidamo Province is having the main stem retracted in the ground like Euphorbia awashensis. Mike Gilbert (pers. comm.) assumes there are number of distinct species included here. In the Flora of Somalia (1993) there is also one record of Euphorbia actinoclada growing in Somalia.
As mentioned before Euphorbia actinoclada is the least problematic species of this group in cultivation. However the two-step-cutting method has not yield a single original growing plant so far. The sowing and raising of seedlings is very rewarding as long as not to much water is giving and a warm and light spot is provided.
Every now and then one can find plants, even in one batch of seedlings, with very different looks. Most of the times the heart of the main stem is open and not covered with lateral branches. As with other plants this central area is tatally covered with branches and the top of the main stem is not visible at all. It appears that the growth rate of the main stem is not rightly tuned with the forming of lateral branches. A plant, seemingly existing of only branches, can be seen on Picture 13.
Euphorbia actinoclada is in The Netherlands in cultivation for a very long time. Some 50 years ago a former Dutch grower, Mr. Bulthuis from Cothen, distributed plants under the name Euphorbia monacantha, which might also be Euphorbia actinoclada. They grow into fairly big and robust plants and are bright green with a lighter pattern on the body. This particular form flowers freely with nice yellow and red cyathia. Since the natural growing place is not known it is now being distributed as Euphorbia actinoclada ‘Bulthuis’.
A somewhat differing form is sold by Specks, Germany, for many years, first as Euphorbia sebsebei and later as Euphorbia species affinis actinoclada, both under salesnumber ES2729. The mixing up with Euphorbia sebsebei is peculiar because this is a totally different species related to euphorbia gemmea amd only known from its type locality along the road from Wachile to Yavello in southern Ethiopia. It could well be that this is the locality where ES2729 originates, which is in the centre of the natural distribution area of Euphorbia actinoclada. A characteristic feature of these plants is that the central area of the main stem is covered with tiny triangular leaves pressed to the stem as scales of a fish.
In recent years many seedlings have been distributed by the writer to other collectors of plants labelled as Euphorbia monacantha GC-98 ’79. These plants, originating of the nursery Grigsby Cactus, are also lacking any habitat information and are resembling ES2729 very much. However the raised seedlings of the one clone I originally had, are very variable.
In recent years I have acquired quite a few different forms of Euphorbia actinoclada from Eastern Europe, all being different in some way or another, just proving Euphorbia actinoclade is a very variable species. It is a pity that their natural habitats cannot be traced anymore. Time will tell whether they all fit into a variable species concept or that more distinct species will be described.
Euphorbia kalisana S. Carter.
Euphorbia kalisana is described by Susan Carter (1982) together with Euphorbia actinoclada. This widespread species occurs in southern Ethiopia and a large part of Kenya, which makes this species the most southernly of the species dealt here with.
Its wellchosen name means in Swahili ‘very sharp’ or ‘very fierce’. Indeed the size of its spines, up to 7 centimeter long, are unique in this group of species. Together with the light green and yellow coloured plantbody makes this species unmistakeable to identify. Both features stay present in cultivation and was prior to its description mostly labelled as E. triaculeata or E. monacantha. As mentioned under Euphorbia triaculeata this species grows fairly big into a untidy bush of 1 meter high. The main stem usually is weakly developed, most of the times hardly higher than soillevel, but can grow as high as 20 centimeters with 7,5 centimeter in diameter. A nice detail is that in its original described is said that the lateral branches of 1 meter long and up to 2 centimeter thick do not re-branch. This feature is written over several times in literature. However on the drawing accompanied to the first description by S. Carter (1992) and on several habitat pictures the opposite is clearly visible. In the Euphorbia Journal (1988) is a beautiful painting reproduced of Dr. Louis Leakey, dating from 1940 representing a lateral branch of this species even has as much as 4 side branches. More than 40 years before its first publication it was named Euphorbia triaculeata.
The most robust forms of this species grow in the more arid regions from the Lake Turkana District, while plants growing on the lower and less arid flats clearly remain behind. Carter and Smith (1988) comment under this species in their flora of a possible distinct form from a small area in the north of Kenya. The lateral branches reach a maximum length of 15 centimeter. This would certainly suites it better for our overcrowded hothouses.
Besides her fierce spination Euphorbia kalisana is characterized by its untidy growthhabit, yellowgreen colouring and rather big big bright yellow cyanthia. Despite being quite difficult to grow in cultivation, Euphorbia kalisana is very beautiful and worth the challenge.
This densely branched form is the most common form form of Euphorbia xylacantha found in cultivation (at least in The Netherlands that is).
This plant of Euphorbia xylacantha shows with its little developed main stem and few thick sidearms, how variable this species can be.
A flowering branch of Euphorbia xylacantha.
Seedlings of Euphorbia xylacantha are one of the most beautiful of all, due to their beauful colouring.
To find this marvellous specimen of Euphorbia xylacantha in nature is a treat few of us will ever have. Near Dire Dawe, nothern Somalia. (Picture Viteszlav Vlk).
Just another Euphorbia xylacantha in habitat. (Picture Viteszlav Vlk).
A very old plant of Euphorbia immersa in the collection of the author.
Although younger plants of Euphorbia immersa are more showy.
Same plant as in picture 22. This view taken from above shows clearly why this species is so appealing to collectors, it is a very compact growing species.
This form of Euphorbia actinoclada from Negele, Etiopia, is frequently found in cultivation. It is easily recognizeable by its bleugreen body colour and its flowers with bright green glands and purple-pink involucre bracts.
Picture 25 and 26.
Euphorbia actinoclada of unknown origin with another colour palets.
Euphorbia actinoclada with entirely yellow flowers is seldom seen ion cultivation.
Picture 28 and 29.
Euphorbia species affinis actinoclada is little different, but the flowers will appear in masses.
Picture 30 and 31.
These two picture show that sometimes the heart of the mainstem is clearly visible and sometimes the heart of the plant is totally covered with sidearms. It seems in no way to affect the well being the plant.
Euhorbia species affinis actinoclada GC-98 ’79 seems to me identical to the plants distributed by Exotica.
Euphorbia species affinis actinoclada GC-98 ’79 flowers also a profusely.
Euhorbia kalisana is characterized by its long light coloured and heavily spined branches with yellow flowers.
I found it quite difficult to take a good picture of the very light yellow flower of Euphorbia kalisana.