Synonyms:

Euphorbia canariensis var. spiralis
Euphorbia canariensis f. viridis
Euphorbia tribuloides
Tithymalus canariensis
Torfosidis canariensis

Habitat:

Euphorbia canariensis is endemic to Canary islands, where it grows in the narrow coastal bells. It is an arid environment from the point of view of rainfall, but there are as well frequent coastal fogs, that create some air humidity. This plant grows in dry lava formations on the south-facing shores in all Canary islands.

Description:

Euphorbia canariensis is a succulent shrub from Canary island, commonly known as “Canary island spurge” or, in Spanish, cardon. In its natural environment, it can reach 3 or 4 meters in height. At a glance, it might be mistaken for a cacti, consisting in a clump of erect, four-angled succulent stems, branching at their very base, at the ground level. Though the Euphorbia genus is totally unrelated to cacti from a phylogenetic point of view, Euphorbia had to develop a similar morphology to face similar environmental conditions, which, in this case, are the semi-arid habitats of Canary islands. This coping mechanism is called convergent evolution and is the reason why Euphorbia are often mistaken for cacti by unfamiliar succulent growers. Euphorbia canariensis, in its natural habitat, forms densely crowded colonies, in which the stems stand out perfectly vertical and upright and numerous: one trunk, branching at its base, can produce up to 150 branches! The single stems are slender, not thicker than a man’s arm. They are 4 or 5-angled, slightly spiralled, smooth and pale green-greyish. On the edges of the ribs, perfectly lined up in vertical rows, there are the spines: brownish-orange and not so long, they grow in opposite pairs.
Flowers are called cyathia. A cyathium (cyathia in the plural form) is one of the specialised false flowers forming the inflorescence of plants in the genus Euphorbia. In E. canariensis they are dark red to purple, 3 to 5 millimeters wide. The cyathia are enveloped by special structures that look like the petals of regular flowers, called cyathophylls that, in this species, are actually fused in one leaf-like structure, with 5 external glands alternating with them.

Cultivation:

Growing Euphorbia canariensis is relatively easy. To ensure optimal growth, it is important to place the plant in a bright spot, such as a sunny window. The plant requires plenty of light to maintain its compact-clump form, and plants placed in shade should be gradually moved to full sun to avoid scorching. It is also important to keep temperatures above 5-8ºC, and in theory, it can survive temperatures down to -6ºC and even a little snow, but it is recommended to keep it indoors during the winter. It is important to make sure the soil is well-drained and dry during the winter to avoid rotting. Water regularly in spring and summer, around once a week, making sure the soil is completely dry before each irrigation. Keep the soil dry during winter, when the plant goes dormant in response to the cold temperatures. The soil should be well-drained, and a mix for succulents is ideal. It is also important to fertilize once a year in summer with a product high in Phosphorus and Potassium and low in Nitrogen, and dilute the product to half the recommended dose. Fertilizing after September is not recommended, as it may cause the stems to become fragile and too wet, which may be fatal during the winter. Euphorbia canariensis is incredibly fast-growing, and its size is often underestimated, so it is important to repot it every year in early spring, and choose pots that are only slightly larger than the diameter of the plant. Remember to wear gloves to protect yourself from the irritating latex contained in its stem. If planted outside, it may become quite large and cause problems later on.

Propagation:

Propagating Euphorbia canariensis is pretty easy, you can do it both by seed and by cuttings. If you want to go the seed route, you’ll need to plant the seeds in well-draining soil and keep them in a warm, bright spot. They should sprout within a couple of weeks. But the most common and easiest way to propagate this plant is by taking stem or leaf cuttings. Just snip off a piece of the stem or leaf during the warmer months of spring or summer, let it dry out for a few days, then plant it in well-draining soil. You can even use rooting hormone to help it along. Keep the cutting in a warm, bright spot and make sure it stays slightly moist until roots have formed, which usually takes around a month. And voila, you’ll have a new E. canariensis plant!

Curiosity:

The latex of Euphorbias is often used in pharmaceutical industry because of its medicinal effects. It is though irritating to skin and mucouses, so we recommend to wear at least a pair of gloves while handling this plant. Euphorbia canariensis, in particular, is one of the more poisonous Euphorbia: it contains a latex rich in diterpenes, considered highly toxic: wear gloves while handling it. The local populations in Canary islands used this species for fuel after drying it up completely. It is also used as a grafting stock for more sensitive Euphorbias.

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