Aloe x spinosissima is one of the oldest and most widely cultivated hybrid aloes, a garden cross between two South African species from the genus Aloe: Aloe arborescens and Aloe humilis. From Aloe humilis it inherits a compact, stemless habit, prolific offsetting, and the raised white tubercles (“spines”) on both leaf surfaces that give the hybrid its name. From Aloe arborescens it inherits larger foliage, vigour, and dramatic orange-red winter inflorescences. The result is a manageable, mid-sized shrub — essentially a dwarf Aloe arborescens — that has been in Mediterranean gardens and Californian collections since at least the early twentieth century. Cold-hardy to approximately −5 to −7 °C (23 to 19 °F), it is a reliable outdoor plant in USDA zones 9b and warmer, and a popular container plant elsewhere. This article covers the nomenclature, description, cultivation and cold hardiness of this enduring hybrid.
Nomenclature and origin
Aloe x spinosissima is a nothospecies (hybrid taxon) of artificial origin, produced by crossing Aloe arborescens Mill. (the krantz aloe, a large, multi-stemmed shrubby species) with Aloe humilis (L.) Mill. (the hedgehog aloe, a small, densely spiny rosette species). Both parents are native to the Eastern Cape and adjacent provinces of South Africa.
POWO (Kew) accepts the name Aloe x spinosissima A.Berger and records the hybrid formula as Aloe arborescens x Aloe humilis. The name was first validly published by Alwin Berger in 1908 in his treatment of the Aloineae in Engler’s Das Pflanzenreich (IV, 38: 247), not by Jahandiez (1933) as sometimes cited. The taxonomy and nomenclature of the hybrid were clarified and the name was neotypified by Gideon F. Smith in 2019, in a paper published in Bradleya 37: 26–30, under the title “The taxonomy of Aloe x spinosissima Hort. ex A.Berger (Asphodelaceae), a popular hybrid aloe from Mediterranean Europe.”
The specific epithet spinosissima is the superlative form of the Latin spinosus (“spiny”), meaning “very spiny” or “most spiny.” Despite this dramatic name, the teeth on the leaves are actually soft, blunt and quite harmless.
The earliest detailed record of the hybrid in cultivation appears in the 1930 publication Cacti and other Succulents: An Annotated List of Plants Cultivated in Santa Barbara, by Hoffman, Orpet, Walther and West. In this book it is listed as a hybrid between Aloe humilis var. echinata (the toothy form of Aloe humilis) and Aloe arborescens var. pachythyrsa — both infraspecific names have since been synonymised with their respective species.
The hybrid is sold commercially under several names: Aloe x spinosissima, Aloe spinosissima (without the “x”, which is technically incorrect), Aloe arborescens ‘Dwarf’, “spider aloe,” and “gold tooth aloe.”
Because both parents belong to Aloe sensu stricto (as redefined by Manning et al. 2014), the hybrid does not require an intergeneric nothogenus formula. It remains in Aloe.
Description
Growth habit
Aloe x spinosissima forms a dense, clumping, multi-rosette shrub, reaching 60 to 90 cm (2 to 3 ft) in height and spreading to 90 to 150 cm (3 to 5 ft) wide over time. The habit is essentially that of a compact Aloe arborescens — a multi-stemmed plant that proliferates from the base through abundant offset production (inherited from the Aloe humilis parent). The stems are short and often hidden by the dense rosettes, giving the plant a more stemless appearance than typical Aloe arborescens. With age, the base can become slightly woody. Growth rate is relatively fast for a succulent.
Leaves
The leaves are arranged in dense rosettes, slightly recurved, lance-shaped, stiff, and pale green to grey-green. They measure approximately 15 to 25 cm (6 to 10 in) long and 3 to 5 cm (1.2 to 2 in) wide at the base. The most distinctive feature — inherited from the Aloe humilis parent — is the presence of raised white tubercles (small, blunt, tooth-like protuberances) on both the upper and lower leaf surfaces, as well as along the margins. These give the foliage a rough, warty texture and the “spiny” appearance referenced in the hybrid name, though they are soft and harmless. The overall effect is of a hurricane-shaped rosette, with the leaf tips curving gently outward and downward, giving the plant a distinctive spiral silhouette.
Under drought or cold stress, the leaves may take on reddish or bronze tones.
Inflorescence and flowers
The inflorescence is a single, unbranched, erect raceme, approximately 40 to 50 cm (16 to 20 in) tall, rising well above the foliage. The raceme is densely flowered and conical. The flowers are tubular, 25 to 35 mm (1 to 1.4 in) long, bright coral-red to orange, and pendulous. The flowering display is dramatic relative to the size of the plant, with multiple rosettes in a mature clump often producing inflorescences simultaneously.
Flowering period
In the Northern Hemisphere, Aloe x spinosissima flowers in late winter, typically January to March. In favourable Mediterranean conditions, a second flush can occur in early summer. The commencement of flowering — when the inflorescence bud appears as a thick, asparagus-like protrusion from the centre of the rosette — is often used by experienced growers as the signal to resume watering after the winter dry rest.
Parent species
Aloe arborescens Mill. — Krantz Aloe
Aloe arborescens is a large, multi-stemmed, shrubby aloe reaching 2 to 3 m (6.5 to 10 ft) in height, with narrow, curved, dark green leaves and spectacular scarlet-red winter flowers. It is the second most widely cultivated Aloe species after Aloe vera, widely grown in Mediterranean and subtropical gardens worldwide. Its cold hardiness is approximately −4 to −5 °C (23 to 25 °F). Native to the Eastern Cape and widely distributed across southern and eastern Africa. Aloe arborescens contributes vigour, larger leaf size, the shrubby habit and the dramatic red inflorescence to the hybrid.
Aloe humilis (L.) Mill. — Hedgehog Aloe
Aloe humilis is a small, stemless, densely offsetting aloe with compact rosettes of short, stiff, triangular leaves bearing conspicuous white tubercles on both surfaces and along the margins. Rosettes reach only 10 to 15 cm (4 to 6 in) in diameter. Flowers are orange to red on slender, unbranched racemes. The species is native to the Eastern Cape of South Africa. Aloe humilis contributes the compact size, the prolific offsetting habit, and the raised tubercles on the leaf surfaces to the hybrid.
Optimal growing conditions
Light
Full sun to partial shade. Aloe x spinosissima performs best in full sun, where the leaves develop their most compact, stiff form and the plant flowers most reliably. In hot Mediterranean climates, light afternoon shade is tolerated and prevents stress colouration, but excessive shade causes etiolation. In cooler, maritime climates (United Kingdom, Pacific Northwest), full sun is essential.
Substrate
Well-draining soil is essential. A standard cactus and succulent mix works well, or a blend of one-third garden soil, one-third compost or potting mix, and one-third coarse sand or perlite. For outdoor planting in Mediterranean zones, ensure excellent drainage by planting on a slope or adding a gravel layer beneath the root zone to prevent winter waterlogging.
Watering
Moderate. Water regularly during the spring and summer growing season, allowing the substrate to dry between waterings (approximately once every 7 to 14 days). Reduce watering in autumn and withhold almost entirely in winter, except for a light watering when the first flower buds appear. The species is drought-tolerant once established.
Temperature
The comfortable growing range is 10–35 °C (50–95 °F). See the cold hardiness section below for frost tolerance.
Feeding
Apply a balanced or cactus-specific fertiliser monthly during the spring and summer growing season. No feeding in autumn and winter.
Propagation
Offset division is the simplest and most reliable method. The hybrid produces offsets abundantly. Detach rooted offsets in spring or early summer, let callous for a few days, and pot or plant in well-draining substrate. Stem cuttings can also be taken where short stems are available. The hybrid can also be grown from seed, though seedlings will show some variation due to the hybrid origin.
Pests
Aloe x spinosissima is notably susceptible to aloe mite (Aceria aloinis), a microscopic eriophyid mite that causes gall-like growths on leaves, flowers and stems. San Marcos Growers notes that this hybrid is one of the plants they monitor continuously for aloe mite. Inspect regularly and remove affected tissue promptly. Mealybugs and scale can also occur but are less problematic.
USDA hardiness zones
Zones 9b to 11b. Some sources extend the range to 9a (minimum −6.7 °C / 20 °F) for established plants in dry soil.
Cold hardiness: documented evidence
Aloe x spinosissima is hardier than most tropical aloes but significantly less hardy than Aristaloe aristata or Aloiampelos striatula. Its cold tolerance is intermediate, roughly comparable to that of its more cold-sensitive parent Aloe arborescens.
Documented reports
San Marcos Growers (Santa Barbara, California): lists winter hardiness as 20–25 °F (−6 to −4 °C). This represents the range for above-ground survival of established plants in the well-drained, low-humidity conditions of coastal California. (Source: smgrowers.com)
Garden Aloes: reports hardiness to 22–25 °F (−5 to −4 °C) and describes the hybrid as “cold-tolerant” but not able to handle “substantial frost.” Notes that it is suitable for outdoor cultivation in the United Kingdom only in very favourable microclimates in urban areas and southwest coastal districts. (Source: gardenaloes.com)
Ripaud Pépinières (France): a French nursery advertises the hybrid as hardy to −7 °C (19 °F). This is the most optimistic published figure and likely reflects a well-established plant in very well-drained Mediterranean soil. (Source: ripaudpepinieres.com)
The Palm Tree Company (United Kingdom): rates hardiness at −3 °C (27 °F) for short periods — a conservative figure reflecting the wet-cold conditions of the British maritime climate. (Source: thepalmtreecompany.com)
Au Jardin (France): recommends bringing potted plants indoors if temperatures drop below −2 °C and notes that young plants may need protection during their first winter outdoors in Mediterranean zones. After two years of acclimatisation in full sun, the plants become significantly tougher. (Source: aujardin.info)
Tropical Britain: describes the hybrid as making “a wonderful houseplant” in cool climates, flowering regularly once it reaches a good size, with the inflorescence appearing in late winter. (Source: tropicalbritain.co.uk)
Dave’s Garden (Coastal Otago, New Zealand, zone 9): a grower reports that both the green and ‘Gold Tooth’ forms “seem very hardy” and are “untroubled by hail,” performing well as fillers in massed succulent displays. (Source: davesgarden.com)
Summary of survival thresholds
| Condition | Estimated threshold | Sources |
|---|---|---|
| Dry soil, established plant, sheltered Mediterranean site | −5 to −7 °C (23 to 19 °F) | Ripaud Pépinières, San Marcos Growers |
| Dry soil, open Mediterranean garden | −4 to −5 °C (25 to 23 °F) | Garden Aloes, San Marcos Growers |
| Moist soil or maritime climate (wet cold) | −2 to −3 °C (28 to 27 °F) | Palm Tree Company, Au Jardin |
As with all succulent cold hardiness, soil moisture at the time of frost is the critical variable. A well-drained, acclimatised plant in a sheltered Mediterranean garden will tolerate significantly colder temperatures than a recently planted specimen in a wet British winter.
Practical recommendations
In USDA zone 10a and warmer, Aloe x spinosissima is fully reliable in the ground year-round. Plant in full sun with good drainage.
In USDA zone 9b, plant only in sheltered microclimates: at the base of a south-facing wall, in raised mineral beds, or on a slope. Protect with fleece or a cloche during forecast frost events. Young plants in their first or second winter are significantly more vulnerable than established specimens — allow at least two growing seasons for acclimatisation before relying on cold hardiness.
In USDA zone 9a and colder, treat as a container plant. Overwinter in an unheated greenhouse, conservatory, or bright indoor room.
Authority links
POWO (Plants of the World Online, Kew): https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:529915-1
GBIF: https://www.gbif.org/species/10720459
iNaturalist: https://www.inaturalist.org/taxa/415128-Aloe—spinosissima
Dave’s Garden: https://davesgarden.com/guides/pf/go/61391
San Marcos Growers: https://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=2038
Garden Aloes: https://www.gardenaloes.com/aloe-spinosissima/
Tropical Britain: https://www.tropicalbritain.co.uk/aloe-x-spinosissima.html
Bibliography
Smith, G.F. (2019). The taxonomy of Aloe x spinosissima Hort. ex A.Berger (Asphodelaceae), a popular hybrid aloe from Mediterranean Europe. Bradleya 37: 26–30. DOI: 10.25223/brad.n37.2019.a24
Berger, A. (1908). Liliaceae-Asphodeloideae-Aloineae. In: Engler, A. (ed.), Das Pflanzenreich IV, 38 (Heft 33): 247.
Manning, J.C., Boatwright, J.S., Daru, B.H., Maurin, O. & van der Bank, M. (2014). A molecular phylogeny and generic classification of Asphodelaceae subfamily Alooideae: a final resolution of the prickly issue of polyphyly in the alooids? Systematic Botany 39(1): 55–74. DOI: 10.1600/036364414X678044
Reynolds, G.W. (1950). The Aloes of South Africa. Balkema, Cape Town.
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes. The definitive guide. Kew Publishing, Royal Botanic Gardens, Kew.
Hoffman, R., Orpet, E.O., Walther, E. & West, J. (1930). Cacti and other Succulents: An Annotated List of Plants Cultivated in Santa Barbara. Ed. Pearl Chase.