Euphorbia pseudoglobosa
Introduction
This dwarf succulent has a nearly geophytic habit, with the stems and branches almost entirely subterranean. It flowers in autumn, when it is adorned with green cyathia.
Fig. 1: A globose specimen of Euphorbia pseudoglobosa in its natural habitat. Photo Marion Maclean
Description
Description
Euphorbia pseudoglobosa is a dwarf succulent or succulent shrub where the tuberous root and main stem form one underground body, with the stem forming a cluster of 6-8 angled, globular to cylindric, narrow-necked branches which are 12-25 mm in diameter. The glabrous rosette of branches is partially covered with obscure tubercles and is green to brown-grey in colour, or red-green for longer branches which become corky below with age. The branches are partly subterranean and in very exposed places only the tips show above the soil. This species can be spiny or spineless, and where spines are present, they are straight, rigid and are about 5-20 mm long, with many, small, alternating bracts. The spines are initially green or red and become grey as they start drying. It is deciduous and the leaves, which appear on tips of new tubercles, are acute and sessile. These leaves are approximately 1 mm long and may be linear to lanceolate. E. pseudoglobosa is unisexual, meaning it has separate male and female plants. Many solitary synflorescences can be found per branch towards the apices, usually with one terminal cyathium (false flower). The cyathia are green, cup-shaped, have 5 deeply serrated lobes and are about 3-4 mm in diameter, with male flowers almost twice as broad compared to female flowers. The ovary, which matures to become the fruit, is globose, glabrous and is raised on a short pedicel. The seed capsule is sessile and has a diameter of 3-5 mm. It is 3-angled, smooth and has a grey-green to red appearance.
Fig. 2: Euphorbia pseudoglobosa displays considerable variation in the shape of the branches, the picture on the left showing a plant with erect, angled branches (Photo Petra Broddle) and the one on the right a plant with shorter, globose branches (Photo Yvette van Wijk)
Euphorbia pseudoglobosa is variable in form and 3 subspecies are recognized: subsp. pseudoglobosa, subsp. vlokii and subsp. nesemanii. The subsp. pseudoglobosa has branches which usually project above the ground for roughly the same length or less than what is submerged beneath the surface, whereas in subsp. vlokii the branches above ground are much more than what is beneath the ground. The subspecies pseudoglobosa has ascending styles whereas these are widely spreading in subsp. vlokii. The last difference between these two is that the inflorescence and outside of cyathia are finely pubescent in subsp. pseudoglobosa while these are glabrous in subsp. vlokii. The third subspecies, nesemannii was previously treated as separate species, Euphorbia nesemannii, and differs from the other subspecies in that it has branches with persistent sterile peduncles. Flowering takes places between April and July in subsp. pseudoglobosa and from May to July in subsp. nesemannii whereas subsp. vlokii flowers most of the year. Euphorbia pseudoglobosa adheres to its autumnal flowering times, regardless of whether it is dry or well watered.
Euphorbia pseudoglobosa is very similar to E. susannae, another Little Karoo endemic, and these two species differ in the position and appearance of the stem. In E. susannae, the stem reaches the surface of the ground , where it is surrounded by the branches which just reach the surface of the ground whereas in E. pseudoglobosa the stem is below the ground and the branches protrude from the surface. The branches of E. susannae are also much shorter and do not taper into a thin neck below the ground. Euphorbia susannae also has tubercles which are much more prominent and taper into slender tips, where E. pseudoglobosa has blunt and flattened tubercles. Euphorbia pseudoglobosa is also somewhat similar to small forms of E. tubeglans but the latter has much more, larger, widely spreading bracts that subtend the cyathia. Euphorbia pseudoglobosa subsp. nesemanii is also quite similar in appearance to smaller plants of E. pillansii but can be distinguished from E. pillansii, which has slightly thicker branches, by the short and simple spines. This subspecies is also superficially similar to E. heptagona and the distinction here is that the branches of subsp. nesemanii are usually much thicker with more angles that are less prominent and fewer, shorter spines. In E. heptagona, the stem is not as short as that of E. pseudoglobosa subsp. nesemanii and the cyathia are attached on peduncles that are much longer than E. pseudoglobosa.
Conservation Status
Status
The Red List of South African plants currently classifies Euphorbia pseudoglobosa as Vulnerable (VU) under criteria B. This species is threatened by habitat loss and degradation due to overgrazing and competition from alien invasive plants in certain subpopulations. The illegal harvesting of wild plants for the specialist horticultural trade is likely to have devastating effects on the persistence of this species in the wild. This species will soon be uplisted to a higher threat status, Endangered (EN), as it now has a smaller population size. All succulent euphorbias, including E. pseudoglobosa, are included in CITES Appendix II.
Distribution and habitat
Distribution description
Euphorbia pseudoglobosa has a restricted distribution in the Western Cape province of South Africa where it is found in the Klein Karoo, from Touws River to Bredasdorp and Barrydale, and parts of the coastal plain to the south of these areas. Plants generally grow on gravelley slopes and flats on shale or quartz patches and outcrops. The different subspecies vary in the habitats they occupy; subsp. pseudoglobosa occurs in arid, exposed spots on flat or gently sloping ground, occasionally in crevices on low shale outcrops. subsp. nesemannii generally occurs on low shaly hills while subsp. vlokii, which is known from a single population, is common on slopes covered with alluvial deposits in red loam.
The Klein (Little) Karoo is a semi-arid to arid area that is characterized by low rainfall, receiving just 100-450 mm per year, due to the rain shadow effects from mountainous regions.
Fig. 3: Euphorbia pseudoglobosa specimen showing the presence of persistent peduncles. Photo Evan Eifler
Derivation of name and historical aspects
History
The name Euphorbia is derived from Euphorbus, who was a doctor to King Juba of Mauretania in Greece. Euphorbus apparently extracted a potent laxative from the cactus-like euphorbias, which prompted King Juba to name the entire group of plants after this physician. Carl Linneaus assigned the name Euphorbia to the entire genus in 1753. However, the name is made up of two Greek words, eu which means ‘well’ and pherbo which means ‘feed’, ‘nourish’ or ‘fat’. The common name for all euphorbias, spurge, comes from Middle English due to the sap of most species being purgative. The word pseudo in pseudoglobosa implies ‘false’ in the Greek language, and globosa refers to the spherical shape of the plant, hence ‘false globosa’.
The family Euphorbiaceae is compromised of over 300 genera and 8 000 species. It is one of the largest dicot families found throughout the tropics. The milky latex is one of the distinctive characteristics of the family Euphorbiaceae. It has a pungent, acrid smell and can result in allergic reactions, blistering and even blindness if the latex comes into contact with the eyes. If latex gets into the eyes, copious amounts of water should be used to wash it off, and medical assistance requested. The latex of some euphorbias releases a scentless, volatile compound which can cause extreme irritation, even in the absence of direct contact. Euphorbias have varied habits, some are thorny, fleshy shrubs, others are large trees with candelabriform branching while others have slender pencil-thick stems growing in tufts. There are over 300 succulent Euphorbias.
Fig. 4: Euphorbia pseudoglobosa in flower, displaying bright green cyathia. Photo Petra Broddle
Ecology
Ecology
Members of the family Euphorbiaceae have a wide variety of pollination systems and pollinator species owing to the diversity of their flowers and inflorescences. Pollination can be abiotic, by wind, in certain genera such as Acalypha, Macaranga, Mallotus, Mercurialis and Ricinus. Species with biotic pollination can be classified into two groups: those where unisexual flowers are visited singly and those in which the flowers are fused into bisexual blossoms and pollinators visit multiple flowers at the same time. In the genus Euphorbia, the species have highly reduced unisexual flowers united in a cyathium. In this case, pollinators visit the clusters of flowers as if they were a single flower. Pollination of these species is usually highly generalized. Pollination by numerous insects in the orders Diptera (flies), Hymenoptera (bees and wasps) and Coleoptera (beetles) has been reported for euphorbias. Bees are said to be more effective pollinators compared to other insects due to their frequent movement on cyathia and their ability to carry pollen. Some species of Euphorbia, such as Euphorbia dendroides, are pollinated by lizards.
While certain species in the family Euphorbiaceae are capable of self-fertilisation, self-fertility has only been recorded from two southern African species, Euphorbia herrei and E. grandidens. Cyathial visitors are attracted in two main ways, by scent, which is given off by the cyathia and by nectar, which is secreted in the cyathial glands. Many of the small members of section Euphorbia in southern Africa have bright yellow cyathia which may be sweetly scented.
The capsules of Euphorbia fruits is typically made up of three locules, with each containing one seed. The capsules take about a month to mature following fertilization. Capsules in euphorbias are schizocarps which typically dehisce explosively. When the capsule dries out, tensions mount along the groove in the midsection of each locule and the locules begin to separate from each other. The tensions are then released abruptly as the locules vigorously break into two down the groove along its middle and locular walls and the seeds are thrown away, only leaving the central column of the capsule attached to the pedicel.
Fig. 5: Euphorbia pseudoglobosa showing 3-angled, grey-green to red fruit capsules. Photo Detlef H. Schnabel
Fire is an ecological requirement for most succulent euphorbias, and is essential for plant growth, mortality and regeneration. Certain species of Euphorbia, such as Euphorbia clivicola, will decline drastically in numbers when an inappropriate fire regime was followed. Fire was also found to stimulate flowering in euphorbias, fire almost tripled the flowering percentage in Euphorbia rosescens in one study.
Uses
Use
Succulent euphorbias make for excellent houseplants, owing to their whimsical growth, and many of these are available in trade. They are popular for their drought-tolerant properties, easy care and distinctive features. These euphorbias are also well suited for outdoor cultivation in mild, dry regions. They thrive under similar conditions to cactuses and are good subjects for desert rock gardens.
Certain species such as E. rayderi, are used as fodder and can be fed to goats and sheep. The latex in Euphorbia can be used to stun fish in ponds, as an ingredient for arrow poisons, as birdlime, for brewing beer and for treating various skin ailments. While E. pseudoglobosa has not been reported as having medicinal properties, the properties of biologically active natural compounds in the latex of many Euphorbia species has led to many Euphorbia species being well known from their medicinal uses. The latex of some euphorbias is used as laxative in small doses and as an emetic in larger doses. The latex of Euphorbia hirta has been found to contain antibacterial, antihelmintic, antiasthmatic, sedative, antispasmodic, antifertility, antifungal and antimalarial properties. Similarly, the latex of Euphorbia tirucalli serves as a blistering agent and rubefacient and is used to treat rheumatism, warts, coughing, asthma, toothache, earache and neuralgia. The latex of species such as E. ingens, E. turicalli and E. triangularis are used in the production of rubber.
Growing Euphorbia pseudoglobosa
Grow
Euphorbias are relatively easy to cultivate and take care of, provided they are kept within their habitat preferences. They experience growth when temperatures are high. They prefer loamy soil which helps prevent the roots from drying up during extended dry periods. Watering should be guided by where the species originates from, with species from moist areas preferring regular watering in summer while those from drier areas can manage with receiving water once a week or even less often than that. Euphorbia pseudoglobosa, like most euphorbias from the winter-rainfall areas prefer to be kept dry during the summer months and prefers water during the winter months. The larger species of Euphorbia prefer being grown outdoors in a decently sized pot in a sunny position.
Seed is the best way of propagation, but unfortunately these are not readily available for Euphorbia species. Seed can be collected from ripe fruits where the capsules are placed in a paper bag and left in a dry, warm place to dry out. Once ripe, the capsules explode forcing the seeds out. The seed coat can then be filed a little and sowed in a tray filled with seedling medium. These should be planted within a month after they have been released but should not be kept for longer than 2 years, as old seed is more difficult to germinate. Seed should germinate within 14 days under warm weather. Once germinated, they will grow rapidly.
A potting mixture containing peat, perlite andvermiculite at a ratio of 2:1:3 or 2:1:4 is recommended for germinating seed. This mixture is effective as it is loose and well aerated and can retain moisture for long periods without becoming waterlogged.
Euphorbias can also be propagated from cuttings, and cuttings toot readily. To make a cutting, a branch must be cut off cleanly where it is constricted at its base and the cut stem must be left to dry out for about a week before being placed into a rooting medium, which should contain river sand. Once planted, this can be firmly propped up with some stones to stabilize the cutting, preventing any movement which can potentially damage the newly formed roots. Regular watering is required at this stage. However, overwatering the cuttings may cause the stems to rot if they remain overly damp. The cuttings should be kept in a well-lit and well-ventilated environment. Rooting can be rapid or may in certain instances take several months before the roots develop.
Species in the Euphorbia genus are generally disease free. Insects may occasionally infest them but in cultivation this can be mitigated by treating plants with a systemic poison containing Imidacloprid. The red spider-mite is a pest that often affects cultivated plants of Euphorbia. They cause a discoloration of the shoot and may spin a web over the surface of the plant as they multiply. Treatment with an acaricide can rid plants of this pests, the use of a biological control agent, often a predatory red mite which feeds of the red spider-mite, is also possible.
Ruschia spp. and Pteronia paniculata are good companion species, as these have been found to grow together with Euphorbia pseudoglobosa in its natural habitat.
References
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Credits
Nokukhanya Nozipho Mhlongo
Threatened Species Programme
July 2023
Acknowledgements: images by Petra Broddle, Evan Eifler, Marion Maclean, Detlef H. Schnabel and Yvette van Wyk, from their observations of Euphorbia pseudoglobosa on iNaturalist.
Plant Attributes:
Plant Type: Succulent
SA Distribution: Western Cape
Soil type: Loam
Flowering season: Autumn, Winter
PH: Acid, Neutral
Flower colour: Green, Yellow
Aspect: Full Sun
Gardening skill: Challenging
Special Features:
Drought resistant
Feature plant
Good potplant
Poisonous
Horticultural zones
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