Euphorbia subgenus Euphorbia section triacanthium
Rikus van Veldhuisen
In this article I want to present to you a group of related species
close to Euphorbia triaculeata.
These species have their natural habitat in North East Africa and the
Arabian peninsula. They are characterized by a short thick mainsprout
with many sidebranches, accordingly to the South African medusoid species.
However this group of species possesses stipular spines, which are absent
in the real medusoid species.
A second important characteristic feature in this related group of species
is that the upper two of four spines are completely or partly fused
to one spine. All species are highly appreciated by specialized growers
of Euphorbias, however they can be very stubborn in cultivation.
The taxonomical place of the section Triacanthium
in the genus Euphorbia. The marking out of the family Euphorbiaceae as one family is
in the last decade in botanical quarters not a subject anymore to heated
discussions. Since the taxonomical review of Grady L. Webster (1994)
of the University of California saw the daylight, is this classification
of the higher taxa in the family of the Euphobiceae widely accepted.
It divides the Euphorbiaceae in five subfamilies. Namely Phyllanthoideae,
Oldfieldiodeae, Acalyphoideae, Crotonoideae and Euphorbioideae. This
last subfamily has our most interest and consists in five tribes, of
which the tribus Euphorbieae is most important. On its turn the tribus
Euphorbieae is divided in three subtribes; Anthosteminae, Neoguillaminiinae
There may be an agreement about the division of the higher taxa in
Euphorbiaceae, this is certainly not the case in the lower taxa.
E. sp. aff. triaculeata AJB D3
with two coloured cyathia
E. sp. aff. triaculeata AJB D3
shows variation in flowercolour.
A one year old seedling of E.
sp. aff. AJB D3 showing the typical growth.
These lower taxa are successively dividerd in sections, subsections, genera,
subgenera, species, subspecies, varieties and formae. Most discussion
is about the genus Euphorbia, the Spurges, which contains by far the most
succulent species and is of course best know by the lovers of succulent
In the wellknown standardwork of Hermann Jacobsen (1977) the succulent
species of Euphorbia are placed in three groups, namely the Pedunculacanthae,
the Stipulacanthae and the Complex M. This last group, Complex M, contains
the species originating from Madagascar. Appearantly he did not know exactly
what to do with this species as it is a very variable group of species.
The Stipulacanthae, which are characterized by the possession of a stipular
spine, are divided in four sections accordingly to the number of spines
at each leafbase, in the case one; Monacanthium Chev., two; Diacanthium
Boiss., three; Triacanthium Jacobsen and four; Tetracanthium Jacobsen.
As one might notice is the making of a botanical classification a job
for anyone who can count the fingers on one hand. Putting a particular
species in a certain section might prove to be a bit more of a problem.
So has the species Euphorbia monacantha given its name to the section
Monacanthae and was originally put into this section. However E. monacantha
is much more closely related to the species of the section Triacanthium.
So this species and E. immersa are put into the latter section.
The remaining species in the section Monacanthae, with its most wellknown
species E. venenifica, are most questionable if the belong at all in the
the group of Stipulacanthae and are perhaps best placed in a group of
The section Triacanthium is not a homogeneous group of species, but can
be divided in two parts. One group has a more southernly distribution
area, concentrated in Kenya and are lacking the short, thickened mainstem.
This species, most wellknown species like Euphorbia similiramea and E.
glochidiata, I will exclude from this article.
The group of species treated here are Euphorbia monacantha ( most known
by its name, but in my opinion not in cultivation today), triaculeata,
schizacantha, xylacantha, immersa, actinoclada, kalisana, awashensis,
erigavensis, margaretiae, myrioclada and the most recently described godana.
Moreover I want to present to you two forms, which are in cultivation,
namely E. species nova Mrs. Ash and E. species 732.
Classification of the higher taxa of the family Euphorbiaceae.
Euphorbia sp. aff. triaculeata. This form with an unclear relationship
form a untidy shrub.
Photo: Guiseppe Orlando.
picture is showing a plant fitting well in the original description
of E. triaculeata.
Photo: Giuseppe Orlando.
Euphorbia triaculeata Forskall.
Since the section Triacanthium thanks its name to euphorbia triaculeata
and furthermore the first species was to be described, it is obvious
we start the dealing of each specie with this one.. As early as 1775
she is described by Forskall on basis of plants origaniting from the
'Çosta dei Miguirtini', nowadays better known as Somalia. Susan
Carter (1987) states that the identity of E. triaculeata is no problem
and that it is still growing on the typelocality, near the shore of
the Red Sea of the Arabian Peninsula. Besides she mentiones that appearently
in the nearby Djibouti the same species grows. This article is supplied
with a nice habitat picture of this species made in Djibouti. These
plants are striking, about half a meter high, sprouting from a depressed
mainstem with sidebranches which form an angle of approximately 45 degrees
with groundlevel. In the accompanying text we find a description of
the plants; about half a meter high, sidearms are 1 to 1,5 centimeter
thick, 3 to 5 ribs and the spines stand on arched podaria. In an article
from Rauh (1966) we find another habitat picture with plants on it with
the same habitus. However I don't know any plants from the typelocality
I take Euphorbia triaculeata to be big plants (0,5 meter high), having
these straight sidebranches with the constant angles and the waving
ribs (arched podaria).
Plants found by Schweinfurth in Eritrea on the flats west of Massana
are described by Pax as Eunphorbia infesta. These plants are taken not
to be different from E. triaculeata and so E. infesta is synonymous.
Other plants found on some islands in the Hamfila Bay before the coast
of Eritrea were described by Ehrenberg as Euphorbia triacantha and later
degradated by N. E. Brown as a variety under E. triaculeata.
Grafted cutting of E. sp. affinis triaculeata collected by Frans
Noltee in Yemen
E. sp. aff. triaculeata
from Yemen, grown from a cutting taken at the cut-two-times method.
It is not 10 centimeters high. This represents the form which originally
came from Eastern Europe.
In our collections there are several forms running around labelled as
Euphorbia triaculeata or E. species affinis triaculeata. Most of them
have an unknown origin or at least insecure, but in my opinion the real
E. triaculata, with the above mentioned identifying features, is rather
scarse. Of all the plants with this species name I came across in some
20 years, plants with the collectionnumber AJB249, collected south-east
of Hays on the Tihama plains, Yemen, did match them the most. This collection
has also the thick more than 1 centimeter thick branches with the arched
podaria on which the spineshields are placed. The cuttings I once grew
in my collection did rebranch quite frequently and strikingly these sidebranches
formed the above mentioned angle of 45 ° and went on growing rather
straight, when not disturbed and do not curve into a vertical position.
Recently plants were sold by Ernst and Maritta Specks as E. triaculeata
and this rooted cuttings do match the plants of AJB 249 quite well. Have
acquired this plant just recently and not knowing its flowers or where
it comes from I cannot say much more about it than that similar plants
ware also distributed by Chuck Hansen in the United States.
Alan Butler, who collected AJB249, made at least two other collections,
designated as Euphorbia (species affinis) triaculeata, which are numbered
as AJB D3 and AJB D10. Both do have much thinner branches.
Euphorbia species affinis triaculeata AJB D3 is collected south of Djibouti-town.
In crosssection branches are circular and the green is slightly marbled
with stripes of lighter green. The flowers are very showy and coloured
bright red and yellow.
Like most, if not all, species in this group is E. species affinis triaculeata
AJB D3 selffertile and seedlings do form the thick depressed mainsprout.
Although sowing is the best way to get a plant with the natural habit,
there is also a vegetative way to achieve this.
Once a branch is rooted it is best to cut off the upper part of it. It
is forced to produce sidebranches if it wants to grow further. If you
are lucky enough this sidebranches show the characteristic features of
a thick short mainsprout. When big enough these sidebranches can be cut
off again and rooted. This socalled cut-two-times method can supply you
with plants with natural habit.
Euphorbia species affinis triaculeata AJB D10 and also E. species nova
Lavr. 13176, Djibouti, will be discussed under the newly described Euphorbia
I grow two different clones of different origine, which are both labelled
as Euphorbia triaculeata, Yemen. One is a gift of a friend from Slovakia
and the other one is collected by Frans Noltee. Unfortunately both have
lost other data on locality or collectionnumber.
The one from Slovakia is a very weak form and the slightly marbled sidebranches
do make the vertical curve upwards on plants with the original mainsprout.
The one collected by Frans Noltee is somewhat thicker and the spimeshields
are placed in ribs and on an elevated foot. Between the ribs is a lightgreen
stripe and all in all I think this is one of the most handsome forms of
all dealt with here.
Overseeing all these forms one can say that many things still needs to
be sorted out and a lot of research in the field needs to be done before
a scientific satisfactory solution is found for all relationsship and
their taxonomic places are filled in. Putting all the weaker forms in
the variety triacantha seems on material availlable in cultivation to