The Diversity of Euphorbia
Many of our favourite species belong to the mind-bogglingly vast Euphorbia genus. This is one of the largest and most diverse groups of plants, with origins across tropical and xeric landscapes, consisting of around 2000 species. It’s amongst the largest of flowering genera, commonly known as 'the spurges' due to their toxic latex sap.
Ranging from small annual plants, to towering tree-like forms, to tiny caudiciform succulents, the genus offers some otherworldly forms which are always a point of intrigue for us. Frequently spotted within our collection, tree-like species like Euphorbia ingens and Euphorbia erythraeae can reach heights of around 9-10 metres in the wild, producing far reaching branches, while others like Euphorbia obesa just about reach 20cm.
Image 01-02. Species of Euphorbia.
Image 03. Mature specimen of Euphorbia ingens. f variegata, heavily branched, towering above most specimens in store at around 3 metres tall.
THE HABITATS
The diversity of the genus is owed to the habitats. Euphorbias thrive in frost-free arid environments, and those dry areas produce the most diverse array of species. Many species from drier environments have the ability to produce wide spreading multi branched plants, but many stay fairly small to camouflage into their surroundings. Their plump bodies help retain moisture in areas with very little annual rainfall.
Image 04-05. Spineless & spiky species of Euphorbia.
Often being labelled as cacti due to their physical resemblance, species of Euphorbia are not cacti, although they are similar in look and care. This is indicated by a lack of areoles that can be seen on cactus species, from where spines grow.
Image 06. Spiky Euphorbia abyssinica, native to arid areas in northern Africa.
Euphorbia species from more temperate climates tend to produce short-lived above ground structures with simple architecture, allowing for their energy to be spent on the rapid growth of their blooms. These species, with origins from the Mediterranean to Nepal or Brazil, are related to the cultivars we grow in our gardens here, which produce wide shrubs with tall blooms.
Image 06. Delicate tufts of leaves grow from stem tips for Euphorbia dendroides, originating from semi-arid areas of the Mediterranean.
Image 07. Blooms on Euphorbia grandialata.
What most species have in common, other than their toxic sap, are the blooms. The flowers occur in a head called cyathium, with no sepals, petals, or nectar. This is unique to the Euphorbiaceae family.
The succulence of this genus from temperate and arid areas doesn’t differ much, however they are not a frost hardy group and most species are found in frost free environments. Even in more temperate climates Euphorbias grow on rocky patches, where water drains from their roots fast.
THE FORMS
TREE-LIKE
Seeing species originating from different climates alongside one another, it can be hard to spot that they are related. Often filling the corners of our stores, tree-like Euphorbia erythraeae originates from Eritrea, in Eastern Africa. Within an arid and semi-arid environment, often experiencing drought, plants have evolved to store water for long periods of time. Fast growing, E. erythraeae produces tall stems with many branches, and masses of short spines. These large structures support the plant in retaining moisture, usually growing to around 4.5 metres tall, some plants have been found to reach heights of more than 9 metres.
Image 08-09. Euphorbia erythraeae & Euphorbia erytraeae f. variegata.
Unlike other species of Euphorbia, lower branches of E. cooperi shed over time leaving just a crown of branches atop a tall solitary trunk. In the wild this species grows primarily through arid wooded grassland and rocky areas from KwaZulu-Natal, through Swaziland and up to Messina in Limpopo. From a grey green trunk bright green branches emerge, irregularly shaped as they become narrow at the end of the growing season before becoming wide again. Protruding ribs are marked with a grey margin and short dark spines.
Image 10. Mature specimen of Euphorbia cooperi.
Image 11. Succulent display featuring Euphorbias at Middleton Mews.
SHRUBS
Image 12. Mature specimen of Euphorbia clava, with delicate foliage and the distinct Euphorbia blooms.
Stretching out its slender stems in all directions, spineless succulent shrublet Euphorbia clava grows to just around 1.5 metres tall, emerging with long delicate leaves along the stem tips. Endemic to the Eastern Cape in South Africa, with a subtropical climate where rainfall is more frequent, meaning Euphorbia clava remains somewhat small and doesn’t need to retain moisture for long.
Image 13. Euphorbia alluaudii.
Cylindrical, spineless branches make up succulent shrub Euphorbia leucodendron (Euphorbia alluaudii), endemic to semiarid or subtropical areas of Madagascar. Producing the tiniest of green leaves at the tips of its stems, which quickly fall off, with their stipules leave behind small brown scales. While juvenile shrubs have many branches with bright green stem, mature specimens has grow a thick woody base, with sparse stems branching only at the top.
Image 14. Euphorbia obesa.
COMPACT
Rather unusal species Euphorbia obesa, the baseball plant, is a succulent species endemic to subtropical Eastern Cape of South Africa able to reach only around 20-30cm tall. Small and plump, this round succulent grows in full sun or under the protection of low shrubs and amongst low boulders in sandy soils.
Its stony and hilly environment means it prefers to grow in a well draining soil. Hot summers and infrequent rainfall mean the plant needs a plump body to retain moisture for periods of drought. Its round shape and brown-green hues helps it blend into its rocky surroundings.
Image 15. Euphorbia neorubella (Monadenium rubellum).
CAUDICIFORM
Growing amongst rocky arid areas in Kenya, this strange caudiciform plant Euphorbia neorubella (Monadenium rubellum) grows slender green (sometimes deep red) branches, twisting together into all directions. Its swollen root at the base, known as a caudex, where the plant stores water and nutrients, adapted to survive long periods of drought or intense conditions. This typically grows underground in the wild, but in cultivation once mature enough this root is exposed due to its curious shape, which can form multiple sections. Pink blooms appear if the plant experiences favourable conditions.
Image 15. Euphorbia tortirama can be found growing within the stony soils in the northernmost province in South Africa. This dwarf succulent emerges with a compact spiny spiralling branches, from a thick tuberous rootstock, growing to only around 30cm.
THE CARE
LIGHT
The key to caring for succulents is light - they love to sunbathe. The most suitable location in our homes is a sunny windowsill, ideally south facing but east or west would also do well. If you notice that your plant’s growth is becoming etiolated, it may be a sign that your plants are not getting enough light. During the hottest and sunniest months of the summer the light can get intense, so look out for any signs of scorching.
Image 16. Mirabeau glasshouse at Middleton Mews.
WATER
Succulent plants with xeric origins are used to periods with little to no rain, and they have a few tricks that take as much advantage of the rain when it does appear. Their thick and waxy stems (or globose bodies) and reduced leaves help retain moisture for these long periods of drought. Their root systems are also often very small in relation to their size, to ensure they are close to the surface of the soil to soak up rainwater.
For most cacti and succulents that we keep in our homes, they will only need regular watering during the active growing season of spring and summer. Water only once the soil has completely dried out. Many will enter a period of dormancy over the winter while conditions are less than ideal, and during this time it’s best to refrain from watering.
FEEDING
Alongside being used to long periods of drought, succulent plants are also used to low levels of nutrients so they don’t require feeding too often. Use a cactus and succulent fertiliser once per month between the months of April and September to encourage new growth and flowering. All feeds will come with measurements and guidance for use.
Image 17. Repotting succulents into terracotta pots, with added drainage medium is ideal.
REPOTTING
Repotting may only be necessary once every 2-3 years (or even longer!) once the plant outgrows its current pot, when roots begin to protrude out of the bottom of the plastic pot. Spring is also the ideal time for repotting. Use a cactus and succulent specific soil mix (with added sand, grit and perlite for extra drainage if needed), plus a pot that’s not much bigger than the previous pot, as they tend to have very small root systems. Pots with drainage holes are ideal.
Image 18. Euphorbia multifolia.
Image 19. Corking developing on a mature specimen of Euphorbia ingens.
REGULAR UPKEEP
Cleaning any dead leaves or debris from the plants or the soil of cacti and succulents reduces the chances of pest or fungus issues. The stems or surfaces can be cleaned with a cloth, or a small brush to get in between all the spiky crevices.
Keep an eye out for pests, such as scale, mealy bug, spider mite, and thrips. Their damage can be reduced if caught early. If pest issues do arise, make sure to isolate the affected plants from the rest of our collection, and treat immediately.
WINTER
Frost is the enemy of succulence. Due to their fleshy interiors the water stored within the bodies of succulent plants freezes, causing expansion and damage to cell walls. This leads to the succulent plants collapsing and turning mushy. During the winter months it’s crucial to keep Euphorbias in a fairly warm space.