Few succulents look less like what they are than Euphorbia canariensis. Its ranks of straight, four- to five-angled columns rising from a common base read as cactus at first glance, yet the plant belongs to Euphorbia, and a single scratch would release the milky latex that no cactus produces. Confined in the wild to the Canary Islands, where it is known as the cardón, it is the dominant woody succulent of the lowland scrub and the official plant emblem of Gran Canaria.
For growers, it is the most architectural of the Macaronesian euphorbias and one of the handsomest columnar species in the genus: symmetrical, slow to disappoint, and capable of turning a dry border into something that looks like a fragment of Tenerife. It is also strictly frost-intolerant in any practical sense, which places it firmly in the warm-climate or container category for most of Europe and North America.
Identification
Habit. A multi-stemmed succulent shrub, woody at the base, 2–4 m tall in habitat. Branches arise at or near ground level from a few suckering trunks, sweeping upward in a shallow curve, so that the lowest part of the arc often rests on the soil. Individual branches rarely branch again, which produces the illusion of a crowd of separate columns rather than a single ramified shrub. Large clumps carry dozens of stems, and figures of up to about 150 branches are quoted for old specimens.
Stems. Columnar, fleshy, of remarkably uniform diameter from base to tip, roughly 8–10 cm across. The cross-section is usually square or pentagonal, occasionally six-angled, and the ribs may run in a slight spiral. Colour ranges from bright green to blue-green and glaucous, ageing to silvery grey on the older wood.
Spines. Paired, short, seated directly on the rib margin in an even vertical row, and curved upward. They emerge reddish-brown and darken with age. Critically, there is no areole: the felted spine cushion of a true cactus is absent.
Leaves. Effectively absent. A minute leaf rudiment, barely a couple of millimetres, may appear at the very tip of a growing column in summer and is shed almost immediately.
Flowers and fruit. The inflorescence is a cyathium, the highly reduced pseudanthium characteristic of the genus, borne singly on very short stalks along the rib edges near the top of the stem. Cyathia open greenish and turn deep red to purplish, which gives flowering colonies their distinctive rusty crowns. Flowering occurs in spring and early summer, with May to July given by Spanish sources. The fruit is a three-parted capsule, red to red-brown, that dries and splits explosively.
Size in cultivation. Considerably smaller than in habitat. Garden references give roughly 1.2–2.4 m in height and 1.2–1.8 m in spread for established landscape plants, with much larger dimensions reached only in frost-free climates over decades.
Hybrids
None is on record. No hybrid involving Euphorbia canariensis is accepted by Plants of the World Online, and none appears in the horticultural literature. The two infraspecific names still circulating in nursery lists, Euphorbia canariensis var. spiralis and Euphorbia canariensis f. viridis, describe variation in rib spiralling and stem colour and are treated as synonyms of the species, not as hybrids or as taxa worth maintaining.
Euphorbia handiensis, the only other cactiform euphorbia in the archipelago, occurs on the Jandía peninsula of Fuerteventura, the same restricted sector that holds the natural population of Euphorbia canariensis on that island. Despite this proximity, no hybridisation has been reported.
Look-alikes and misidentifications
The first and largest error is the family. Anyone offered a cardón as a “Canary Island cactus” is being sold an Euphorbia. Check the spines: paired, sitting bare on the rib, no areole, no glochids.
Within the genus, the species most often confused are these.
Euphorbia handiensis is smaller, rarely exceeding 1 m, with more numerous and blunter ribs and far longer spines, commonly 3 cm and up to 5 cm, that whiten with age. It is also one of the rarest euphorbias in cultivation, so a large, cheap, long-spined plant is unlikely to be this species.
Euphorbia officinarum subsp. echinus, from southern Morocco, builds dense hemispherical mounds of short, finger-like stems. The overall silhouette is a cushion, never a candelabrum.
Euphorbia resinifera, also Moroccan, does share four-angled stems with paired spines, and young plants can genuinely mislead. It stays at 1–1.5 m and spreads laterally into low, wide mats. It is also far hardier, which is why the two should never be treated as interchangeable in a garden.
The large African tree euphorbias sold for Mediterranean gardens, among them Euphorbia ingens, Euphorbia ammak and Euphorbia abyssinica, have a single defined trunk, thicker and distinctly winged branches, and a far coarser texture.
Finally, the Canarian tabaibas that share its habitat, Euphorbia balsamifera, Euphorbia lamarckii and Euphorbia regis-jubae, are leafy, spineless shrubs and pose no real identification problem in the field.
Taxonomy and nomenclature
Euphorbia canariensis was described by Linnaeus in Species Plantarum, volume 1, page 450, published on 1 May 1753. Its IPNI identifier is 345920-1, and the name is accepted by Plants of the World Online.
Five synonyms are recognised. Two are homotypic, based on the same type as the Linnaean name: Tithymalus canariensis (L.) H.Karst. and Torfasadis canariensis (L.) Raf. Three are heterotypic: Euphorbia tribuloides Lam., Euphorbia canariensis var. spiralis Bolle ex Boiss. and Euphorbia canariensis f. viridis G.Kunkel.
The generic name commemorates Euphorbus, physician to Juba II of Mauretania, credited in classical tradition with recognising the medicinal properties of certain spurges; the epithet simply states the plant’s origin.
Molecular work on the genus places the species in subgenus Euphorbia, the large Old World succulent clade, together with Euphorbia handiensis. This matters for understanding the Canarian flora: the other spurges of the archipelago belong elsewhere in the genus, with Euphorbia balsamifera in subgenus Athymalus and the arborescent tabaibas in subgenus Esula. The islands were therefore colonised several times independently by different euphorbia lineages rather than once, followed by local diversification.
In the wild
The species is endemic to the Canary Islands, where it occurs on El Hierro, La Palma, La Gomera, Tenerife, Gran Canaria and Fuerteventura. It is absent, or extinct as a wild plant, on Lanzarote, where its native status has long been questioned, and it does not occur on the Chinijo islets or on Lobos. Outside its native range, Plants of the World Online records it as introduced in Tunisia.
It is frequent on the western islands, particularly Tenerife, and on Gran Canaria. On Fuerteventura it is genuinely rare, restricted in nature to the Jandía peninsula and the area around Montaña Cardones.
Its ground is rocky slopes, scree and lava fields in arid to semi-arid country, from sea level to about 900 m and locally a little higher, at the lower edge of the pine belt. Rainfall is low, but coastal fog supplies regular atmospheric moisture, a detail that explains why the species tolerates humid air far better than wet soil.
Euphorbia canariensis is the structuring species of the cardonal, the lowland community it shares with Euphorbia balsamifera, Euphorbia lamarckii, Euphorbia regis-jubae, Periploca laevigata, Kleinia neriifolia, Rubia fruticosa and various Asparagus.
An old clump is a habitat in its own right. Its dense, armed stems shelter native plants that would otherwise be grazed out by introduced herbivores, and specialised invertebrates depend on it, notably the cardón longhorn beetle Lepromoris gibba, whose larvae develop exclusively in dead stems. Clumps average around 30 m² of ground cover, and exceptional individuals exceed 100 m². Reproduction is by seed, dispersed explosively when the capsules dry, and vegetatively when detached stem segments root where they fall, which is how dense clonal colonies form.
The species is assessed as Least Concern on the IUCN Red List. It is listed on CITES Appendix II, like all succulent euphorbias not covered by Appendix I, and on Annex II of the Canarian flora protection order of 20 February 1991, under which collection, nursery propagation, movement between islands and reintroduction all require prior authorisation.
Outdoor / in-ground cultivation
In-ground planting makes sense only where winters are essentially frost-free: coastal southern California, the frost-free fringe of the Mediterranean coast, subtropical Australia, and comparable climates. Elsewhere the species is a container plant that summers outdoors.
Siting. Full sun, with at least six hours of direct light. In shade the columns etiolate, lose their even diameter and lean. Choose a position sheltered from cold wind and, in marginal areas, close to a south-facing wall that radiates stored heat at night.
Soil. Sharp drainage is not negotiable. On heavy ground, plant on a raised mound or in a gravel-based bed rather than attempting to amend a flat clay site. Slope helps more than any additive.
Spacing. Allow generously for lateral spread. The clump widens by suckering, and crowded plants become impossible to maintain without contact with the latex. A minimum of 2 m from paths, doorways and play areas is sensible.
Water. Deep but infrequent irrigation through the growing season, none in winter. Established plants in a Mediterranean climate need almost nothing in summer once the root system is out.
Maintenance. Very little. The species is largely untroubled by pests outdoors and is generally listed as deer- and rabbit-resistant, which the latex makes entirely plausible. Remove dead or storm-broken columns at the base, working with gloves and eye protection.
Safety. This is the one point that should govern placement. The latex is caustic on skin and hazardous to eyes. A plant beside a driveway where car doors open, or at child height along a path, is a poor design decision regardless of how good it looks.
Container cultivation
Containers suit the species well, and a large pot slows it enough to keep it manageable for many years.
Substrate. A mineral mix: pumice, lava grit or coarse sand with a small organic fraction, no more than a quarter of the volume. Avoid peat-heavy commercial composts, which stay wet at depth.
Pot. Wide and heavy rather than deep. A mature clump is top-heavy and will tip a plastic pot in wind. Terracotta helps the substrate dry between waterings.
Watering. From spring to late summer, water thoroughly and then wait until the mix is bone dry. From autumn, taper off; through winter, keep completely dry. Cold and wet together kill this plant; cold and dry rarely do.
Feeding. A low-nitrogen succulent fertiliser once or twice during the growing season is ample. Excess nitrogen produces soft, pale growth that marks and rots easily.
Repotting. Every three or four years, in early spring. Wear gauntlets, long sleeves and goggles; the branches break easily and bleed freely.
Overwintering. A bright, dry, frost-free space at 7–10 °C is ideal. A dark garage works less well than a cool conservatory, as the plant retains its columns and will etiolate or spot if kept warm and dim.
Sun acclimatisation. Move plants outdoors in stages over two or three weeks in spring. Sudden full exposure after a winter indoors scorches the epidermis, and the scars remain visible for years.
Grafting. The species is used as a stock for slow, difficult euphorbias, Euphorbia lorifolia being the example most often cited in the specialist literature.
Propagation
Seed is the reliable route. Sow in spring in a mineral medium at 20–25 °C, keeping it barely moist. Germination is uneven and seedlings are slow, but plants raised this way are better rooted and better shaped than cuttings.
Cuttings are possible but have a poor reputation in this species. Sever a column, rinse the cut surface to stop the latex flow, then callus the piece dry, shaded and in open air for one to three weeks depending on thickness before setting it in barely moist mineral substrate. Francophone growers report repeated failures with small-diameter cuttings, which either desiccate without rooting or mould during callusing. Thick cuttings taken at the start of the warm season perform noticeably better.
Natural layering occurs in habitat, where fallen stem fragments root spontaneously, and can be exploited in the garden by pinning a low branch onto gritty soil.
Pests and diseases
Cultivated plants are usually lost to conditions rather than organisms.
Basal and root rot is the main cause of death, driven by water-retentive substrate or winter watering. A stem softening at the base should be cut back to firm tissue; the sound upper portion can be treated as a cutting.
Mealybugs colonise the grooves between ribs and the base of the spine pairs, where they escape notice for months. Root mealybugs usually come to light at repotting.
Spider mites produce grey, corky patches on young growth in hot, dry, still air, typically under glass.
Cold marking is not a disease. Brown to black patches following a chill are permanent parenchyma damage; superficial ones are cosmetic and do not threaten the plant.
Lepromoris gibba, the longhorn beetle associated with the species in the wild, attacks only dead stems and is irrelevant in cultivation.
Cold hardiness
Published figures should be read with the plant’s origin in mind. The cardonal belt of the Canaries is effectively frost-free, so all hardiness data for this species come from cultivation, not from habitat, and none of it rests on a long observational series.
The French reference site Au Cactus Francophone gives a brief tolerance of about -2 °C while recommending that plants be kept above 7 °C to remain in good condition. English-language compilations derived from Dave’s Garden are more generous, placing the species around -3.9 °C and quoting USDA zones 9b to 11b. That zone range is optimistic: zone 9b implies annual lows near -3.9 °C, which is precisely the point at which the species starts to mark badly.
A 2022 discussion of overwintering large euphorbias on the Au Cactus Francophone forum addresses this discrepancy directly. Contributors growing in low-mountain conditions in the Aude, southern France, and overwintering their collections in greenhouses held at +6 °C, conclude that in regions with wet, dull winters the species should simply be kept above freezing. Sub-zero exposure will often not kill the plant, but it leaves irreversible staining and disfigurement. Photographs of in-ground plants posted on the Italian forum Cactofili give no locality or climate data and cannot be used to establish a hardiness figure.
The practical rule: treat 5–7 °C as the working minimum for an unblemished plant, accept brief dips to around freezing as a risk rather than a specification, and remember that winter wet is a greater threat than winter cold on its own.
Traditional uses
The cardón carries one of the best-documented bodies of traditional knowledge in the archipelago, compiled in the Spanish national inventory of traditional knowledge relating to biodiversity.
Fishing. The best-known use is embarbascado: crushed stems thrown into coastal rock pools or barranco pools, where the latex stunned fish, octopus and eels. Attributed to the pre-Hispanic population, it appears in the archives from the sixteenth century onward and persisted locally until the mid-twentieth. It is now prohibited.
Human medicine. The latex was used to cauterise fistulas, wounds and ulcers, to burn off warts and corns, and to treat skin tumours, with the surrounding skin protected by olive oil or goat’s milk. A drop was applied to an aching tooth. Mixed with oil, it went into chest poultices and preparations for boils and eczema. Taken internally it was regarded as a drastic purgative and emetic, and the older sources describe it with explicit warnings.
Veterinary medicine. It was applied widely to udder complaints in livestock, especially mastitis, and to mange in horses and various abscesses.
Materials and daily life. Firewood; smoking cheese on Tenerife; enclosure walls for livestock pens; dried stems as animal bedding for manure production; hoops for sieves and handles for baskets, made from unbranched stems fired and then soaked; hoops for tajaraste drums; birdlime for trapping. Latex was even applied to grapes to deter thieves, the culprit betrayed by swollen lips.
Other. The species has beekeeping value in arid zones, the honey being described as bitter and slightly pungent, and goats eat the inflorescences on Tenerife. Against latex burns, Canarian country practice used the sap of Periploca laevigata or Aeonium lindleyi, or olive oil poultices.
Symbolism. The cardón became the official plant emblem of Gran Canaria by decision of the Canarian Parliament on 17 April 1991, and it appears on the municipal arms of Santiago del Teide, adopted in 1986. The celebrated cardón of Buenavista del Norte on Tenerife, which caught Humboldt’s attention when he passed through in 1799 and covered some 148 m², survives only as fragments but remains on the town’s coat of arms.
FAQ
How fast does it grow? Slowly by garden standards, though not glacially. Landscape references suggest a substantial plant in three to five years under frost-free conditions with adequate summer water. In a container, expect a few centimetres of column extension a year.
Can I plant it outdoors in USDA zone 9b? Not safely. The zone listings that include 9b assume the plant survives its rated low, but survival and remaining presentable are different outcomes. In 9b, plan on a container.
Is it deer- and rabbit-resistant? Yes, and the reason is the latex rather than the spines. This makes it useful in rural gardens where browsing pressure rules out softer succulents.
How dangerous is the sap? Enough to justify eye protection. It is caustic on skin and can cause serious eye injury. Historical Canarian accounts even record irritation from the fumes during bulk harvesting. Rinse eye contact copiously and seek medical advice.
How do I tell it from Euphorbia handiensis in a nursery? Spine length. Euphorbia handiensis has spines of 3 cm and more; those of Euphorbia canariensis are around a centimetre. Size and price also differ, since Euphorbia handiensis is rare in cultivation.
Is it legal to buy? Yes, from nursery-propagated stock with the appropriate CITES Appendix II documentation. Collecting wild material in the Canaries is prohibited under regional law.
Why are the tips of my plant turning red? Often nothing more than sun stress or cool nights, both of which redden the epidermis reversibly. Persistent dark, sunken patches after cold exposure are permanent scarring instead.
Bibliography
Linnaeus, C. 1753. Species Plantarum, 1: 450. Impensis Laurentii Salvii, Stockholm. [Protologue. In keeping with the work’s format, the name is published with a very brief diagnosis and references to earlier literature rather than a full morphological account.]
Govaerts, R., Frodin, D. G. & Radcliffe-Smith, A. 2000. World Checklist and Bibliography of Euphorbiaceae (and Pandaceae), 4 vols. Royal Botanic Gardens, Kew. [The global nomenclatural checklist for the family and one of the sources POWO follows in accepting this name and its synonymy.]
Sauerbier, H., Cabrera Calixto, F. & Muer, T. 2023. Flora Vascular de Canarias. Turquesa, Santa Cruz de Tenerife. [The most recent flora of the archipelago, also followed by POWO. The standard modern treatment of the Canarian vascular flora.]
Bramwell, D. & Bramwell, Z. 2001. Flores silvestres de las islas Canarias, 4th ed. Rueda, Madrid. [Long-established field flora, widely cited for Canarian vernacular names and for the ecology of the lowland communities.]
Beech, E. 2017. Euphorbia canariensis. The IUCN Red List of Threatened Species 2017: e.T79727248A79727254. doi:10.2305/IUCN.UK.2017-3.RLTS.T79727248A79727254.en [Least Concern assessment, based on a wide distribution and populations that are not severely fragmented.]
Álvarez Escobar, A. & Rodríguez Delgado, O. Euphorbia canariensis L. In: Inventario Español de los Conocimientos Tradicionales relativos a la Biodiversidad, pp. 161–165. Ministerio para la Transición Ecológica, Madrid. [The reference ethnobotanical synthesis, with notes citing more than ninety primary sources. The year of publication does not appear on the offprint consulted online and is therefore not given here.]
Álvarez Escobar, A. 2011. Contribución al estudio etnobotánico de la isla de Tenerife. [Fieldwork underlying most of the Tenerife records reproduced by the national inventory and by CONECT-e.]
Bruyns, P. V., Klak, C. & Hanáček, P. 2011. Age and diversity in Old World succulent species of Euphorbia (Euphorbiaceae). Taxon, 60(6): 1717–1733. doi:10.1002/tax.606016 [Reference molecular phylogeny for the Old World succulent spurges. Places Euphorbia canariensis and Euphorbia handiensis in subgenus Euphorbia, separate from the lineages containing the Canarian tabaibas.]
Bruyns, P. V., Mapaya, R. J. & Hedderson, T. 2006. A new subgeneric classification for Euphorbia (Euphorbiaceae) in southern Africa based on ITS and psbA-trnH sequence data. Taxon, 55(2): 397–420. [Establishes the four-subgenus framework now in general use, within which the placement above is read.]
Viera y Clavijo, J. de. Diccionario de Historia Natural de las Islas Canarias. [Eighteenth-century source containing the classic account of the latex, its causticity and the antidote drawn from Periploca laevigata, repeated throughout the later Canarian literature.]
Orden de 20 de febrero de 1991, sobre protección de especies de la flora vascular silvestre de la Comunidad Autónoma de Canarias. Boletín Oficial de Canarias 35, 18 March 1991. [The regulation listing the species on Annex II, under which collection, nursery cultivation, movement between islands and reintroduction require prior authorisation.]