Aloiampelos striatula

Aloiampelos striatula is the hardiest shrubby alooid in existence — a robust, scrambling succulent that forms dense thickets of striped stems and dark green recurved leaves on the cold mountain summits of the South African Karoo and Lesotho. Long classified within the genus Aloe, molecular phylogenetic evidence placed it in the genus Aloiampelos (the “scrambling aloes”), a lineage that separated early from the main alooid radiation. Unlike the compact rosette species of Aristaloe or Gonialoe, Aloiampelos striatula is an architectural shrub reaching two metres tall, capable of forming colonies more than five metres across. Established plants have been documented regrowing from underground rootstock after exposure to −18 °C (0 °F) in southern England. Its yellow to orange-red summer flower spikes attract sunbirds and bees. This article covers the taxonomy, ecology, morphology, cultivation and — in extensive detail — the real-world cold hardiness of this remarkable species.

Taxonomy and botanical history

Aloiampelos is a genus of seven species of scrambling (rambling) succulent shrubs in the family Asphodelaceae (subfamily Asphodeloideae). The genus name combines Aloe with the Greek ampelos (“climbing plant”), reflecting the scrambling growth habit shared by all members. The genus was formally established by Grace, Klopper, Smith et al. in 2013 (Phytotaxa 76: 7–14), based on molecular phylogenetic evidence showing that the scrambling aloes (formerly Aloe section Macrifoliae) form an early-branching lineage within the alooid clade, separate from Aloe sensu stricto.

Aloiampelos striatula was originally described as Aloe striatula by Adrian Hardy Haworth. The specific epithet striatula means “with small stripes” in Latin, referring to the distinctive dark green longitudinal stripes visible on the stems and leaf sheaths — the most immediately recognisable diagnostic feature of the species.

POWO (Kew) recognises two varieties:

Aloiampelos striatula var. striatula — the type variety, with dark green leaves and reddish-orange to yellow flowers. Widespread.

Aloiampelos striatula var. caesia (Reynolds) Klopper & Gideon F.Sm. — described by Reynolds in 1936 (Flowering Plants of South Africa 16: t. 633). Distinguished by shorter, greyer (glaucous) leaves and bright yellow flowers. Found only around the town of Molteno in the Eastern Cape. Rarer in cultivation but reported by some growers to be slightly hardier than the type.

Nomenclatural synonyms: Aloe striatula Haw. — basionym. Aloe striatula var. caesia Reynolds.

Common names: “hardy aloe” (the most common English name, reflecting its outstanding cold tolerance), “striped-stemmed aloe” (descriptive of the stem markings). In the Eastern Cape and Lesotho, the species is used as a hedge plant around livestock kraals.

Ecology

Native range

Aloiampelos striatula is indigenous to the mountains of the Eastern Cape, extending into the southwestern Free State and into Lesotho. Tropical Britain describes the natural range as stretching from Graaff-Reinet in the west to Queenstown in the east, north to Aliwal North and across the Orange River into the Free State and Lesotho, “often at very high elevations.” SANBI notes that it also occurs on the Free State-Lesotho border. The highest point of its range approaches the summits of the Stormberg Mountains in the Eastern Cape — near the site of South Africa’s only ski resort.

Habitats

Aloiampelos striatula grows among rocks on mountain summits within the winter snow belt. SANBI describes it as growing in grassland, thicket and on rocky outcrops, often on the ecotone between different vegetation types. Unlike most Aloiampelos species (which are largely coastal), Aloiampelos striatula is an inland, high-altitude species — a key factor in its exceptional cold hardiness.

In the Eastern Cape, it is traditionally planted along the boundaries of kraals (livestock enclosures), where it naturally forms a well-shaped, impenetrable hedge. Its scrambling habit and ability to root from fallen stems make it an effective living fence.

Climate in habitat

The mountains of the eastern Karoo and the Stormberg range experience a climate of hot, dry summers and very cold winters.

Winter (May–August): frequent frost and occasional snowfall on higher ground. Minimum temperatures regularly drop to −5 to −10 °C (23 to 14 °F), with exceptional lows of −15 °C (5 °F) or lower at the highest elevations. The Tropical Britain description explicitly places the species in the heart of the Stormberg snow belt.

Summer (November–February): hot and dry, with temperatures usually exceeding 30 °C (86 °F). Rainfall is moderate, falling mainly as summer thunderstorms (500–700 mm / 20–28 in per year).

This cold, continental montane climate — with dry freezing winters and warm wet summers — is the key to the species’ legendary cold hardiness.

Description

Growth habit

Aloiampelos striatula is a robust, multi-stemmed, scrambling shrub that can reach up to 2 m (6.5 ft) in height and spread considerably wider — mature colonies of 5 m (15 ft) or more across have been documented. The stems are semi-erect to sprawling, branching freely. They become woody with age. Fallen or leaning stems root readily on contact with soil, allowing the plant to form dense, self-reinforcing thickets. The stems display the characteristic dark green longitudinal stripes (on both the stem surface and the leaf sheaths) that are the defining visual feature of the species.

The plant has a vigorous root system. When the above-ground growth is killed by severe frost, the plant can regenerate from the rootstock — a survival strategy shared with several other montane alooids.

Leaves

The leaves are dark green, strongly recurved (curving back from the stem), lanceolate, and approximately 25 cm (10 in) long. They are fleshy but relatively flat and narrow for an alooid. They are arranged spirally along the stem, densely packed, covering the stem from base to tip when well-watered or only at the apex when drought-stressed. The margins bear numerous small, widely spaced white teeth. The leaf sheaths are distinctly striped with dark green longitudinal lines.

Under Mediterranean climate conditions, the leaves lose their turgidity during the dry summer months, becoming noticeably thinner and flaccid as the plant depletes its water reserves. This is not a sign of ill health but a normal seasonal response consistent with the species’ adaptation to hot, dry summers in the Karoo. Full turgidity returns rapidly with the first autumn rains, and the leaves regain their firm, fleshy texture within days of rehydration.

Inflorescence and flowers

The inflorescence is an unbranched, dense, conical raceme up to 40 cm (16 in) tall, carried on an erect stem emerging from the leaf rosette at the stem tip. The racemes are densely flowered — more so than most other Aloiampelos species.

Flower colour varies with variety and form: in var. striatula, the flowers are typically reddish-orange; in var. caesia, they are bright yellow. Intermediate shades of orange and yellow occur. The flowers are tubular, with protruding orange stamens. They are rich in nectar and attract sunbirds (the primary pollinators in habitat), as well as bees.

Flowering period

In the wild (Southern Hemisphere), Aloiampelos striatula flowers throughout the summer months (November to February). In Northern Hemisphere cultivation, flowering occurs from late spring through summer, typically May to August. The RHS describes the flowering period as “summer.” Some growers in mild Mediterranean climates report intermittent flowering from autumn through winter as well. SANBI notes that the species is “often shy to flower in cultivation” — possibly due to insufficient light intensity or lack of the natural temperature differential between hot days and cold nights that the plant experiences in habitat.

Comparison with two related species

Aloiampelos striatula vs Aloiampelos commixta (A.Berger) Klopper & Gideon F.Sm.

Aloiampelos commixta is the closest relative of Aloiampelos striatula, restricted to the Cape Peninsula (Table Mountain and surroundings). It is classified as Vulnerable (VU).

Key differences:

Leaf posture: leaves of Aloiampelos commixta are borne erectly, pointing toward the growing tip. Those of Aloiampelos striatula are strongly recurved.

Stem stripes: while Aloiampelos commixta has “striatulate sheaths” (subtle striping), the stripes on Aloiampelos striatula are far more prominent and diagnostic.

Inflorescence: Aloiampelos commixta has a short, almost capitate, bicoloured raceme on a stout peduncle (15–17 mm diameter). Aloiampelos striatula has a tall, conical, densely flowered raceme on a thinner peduncle.

Distribution and hardiness: Aloiampelos commixta is coastal and subtropical (Cape Peninsula); Aloiampelos striatula is inland and montane. Aloiampelos striatula is dramatically hardier.

Aloiampelos striatula vs Aloiampelos ciliaris (Haw.) Klopper & Gideon F.Sm.

Aloiampelos ciliaris (the climbing aloe) is the most vigorous climber in the genus, commonly grown as a fast-growing ornamental in Mediterranean climates.

Key differences:

Growth rate: Aloiampelos ciliaris is much faster-growing and more vigorous, reaching several metres in length. Aloiampelos striatula is more compact and shrubby.

Leaf cilia: Aloiampelos ciliaris has distinctive soft white cilia (hairs) along the leaf margins and at the base of the leaf sheaths — the feature that gives it its name. Aloiampelos striatula has small white teeth, not cilia.

Cold hardiness: Aloiampelos ciliaris is considerably more frost-tender (approximately −3 to −5 °C / 23 to 27 °F). Aloiampelos striatula is far hardier (documented survival to −12 °C above ground, −18 °C from rootstock).

Ease of flowering: Aloiampelos ciliaris flowers freely and reliably in cultivation. Aloiampelos striatula can be shy to flower, especially in low-light conditions.

Optimal growing conditions

Light

Full sun. Aloiampelos striatula grows on exposed mountain summits in South Africa and demands maximum light intensity. In partial shade, it becomes leggy, pale, and reluctant to flower. In the hottest Mediterranean climates, light afternoon shade is acceptable.

Substrate

Well-drained soil. The species is less demanding about substrate composition than rosette alooids — SANBI recommends “heavy soil” (i.e. garden loam) rather than the extremely mineral mixes required by desert species such as Gonialoe dinteri. The key is that the soil must drain freely; waterlogging is fatal. Adding coarse sand, pumice or perlite to standard garden soil is usually sufficient.

Watering

Regular watering during summer promotes strong growth and flowering. Unlike many alooids, Aloiampelos striatula benefits from consistent summer irrigation — it comes from a summer-rainfall climate. In winter, reduce watering but do not withhold it entirely. The species is tolerant of moderate winter rainfall provided drainage is good.

Temperature

Very cold-hardy for an alooid. The comfortable growing range is 5–35 °C (41–95 °F). The species tolerates prolonged frost and light snow. See the detailed cold hardiness section below.

Feeding

Moderate. Apply a balanced general-purpose fertiliser once or twice during the growing season (spring and summer). The species responds well to feeding, unlike many of the more specialised desert alooids.

Propagation

Stem cuttings (truncheons) are the easiest and fastest method. Cut a stem section 15–30 cm long, allow it to callous for a few days in shade, then plant directly into the ground or into a pot of well-drained soil. Cuttings root rapidly, even in winter. Seed propagation is also straightforward at 20–22 °C (68–72 °F). Plants can also be divided or layered.

Pruning

Regular pruning is recommended to maintain a compact shape. Without pruning, the stems become long and sprawling, eventually collapsing under their own weight. Cut back stems when they reach approximately 60 cm (2 ft) — this promotes branching and a denser, bushier habit. Pruned material can be used as cuttings. Note, however, that hard pruning (cutting back to ground level) should be done cautiously: some growers report that the plant is slow to “fire back” from severe cutting.

USDA hardiness zones

Zones 8b to 11b (World of Succulents, Plant Lust). Some sources rate it as low as zone 7 with root survival.

Cold hardiness: documented successes and failures

Aloiampelos striatula has the most extensive documented cold-hardiness record of any shrubby alooid. It is widely grown outdoors year-round in the United Kingdom, the Pacific Northwest of the USA, and coastal Europe, generating a large body of grower experience.

Documented reports

Agaveville forum — Hardy Aloes thread (England): a contributor in England states that Aloiampelos striatula “takes the gold medal for being the toughest” aloe, ahead of all other species tested. The same contributor notes that a mature, established plant was documented regrowing from underground rootstock after −18 °C (0 °F) in southern England during the severe winters of the 1980s. (Source: agaveville.org)

Agaveville forum — Pushing the Limits thread: Paul S confirms that above-ground growth is damaged at approximately −6 °C (21 °F) or so, but reliably resprouts in spring from older stems. Established plants have regrown from underground after −18 °C (0 °F). He adds that the variety caesia is a “teeny bit hardier” than the type. (Source: agaveville.org)

Urban Jungle Plant Nursery (United Kingdom): reports that Aloiampelos striatula survived harsh winters at the nursery. During the 2009/10 winter, above-ground growth was killed to ground level, but new growth re-emerged in late spring and regrowth was rapid. (Source: urbanjungle.uk.com)

Tropical Britain: describes the species as “hardy in much of the UK and like some Opuntias, it often copes with winter stress by” dying back above ground and regrowing. The nursery notes that the species naturally occurs near the highest point in the Cape Province, within the Stormberg snow belt. They consider Aristaloe aristata to be somewhat hardier overall (since it does not lose its above-ground growth). (Source: tropicalbritain.co.uk)

Dave’s Garden (Southampton, United Kingdom): a grower reports that the species survived −9 °C (16 °F) with no damage to above-ground growth — describing it as “really the only tall-growing aloe that is reliably hardy in the milder parts of the UK.” (Source: davesgarden.com)

Dave’s Garden (Zone 8b, British Columbia, Canada): “this Aloe/Aloiampelos sailed through winter like nothing happened. We had snow and ice and it didn’t even flinch.” (Source: davesgarden.com)

Dave’s Garden (unspecified location): a plant was reported dead after a three-day freeze at −9 °C (16 °F), highlighting that duration matters as much as minimum temperature. (Source: davesgarden.com)

Plant Lust (multiple nurseries): various listings report hardiness to 15 °F (−9 °C) for above-ground survival, with resprouting from roots at 0 °F (−18 °C) for established plants. One nursery (Cistus Nursery, Portland) rates it as “hardy to at least 10 °F once established.” Another notes “top hardy to 18 °F, upper USDA zone 8; has resprouted from 0 °F zone 7, or below with mulch, good drainage, and protection from winter moisture.” (Source: plantlust.com)

Hardy Tropicals UK forum: “striatula got cut back to the ground this winter but is now multi stemmed and bigger than last year!” Another grower: “striatula like aristata are very hardy down south and need no protection down to −12 °C as long as they’re treading on grit.” (Source: hardytropicals.co.uk)

My Mediterranean Garden: reports hardiness to −12 °C (10 °F) in well-drained soil. Notes that cold, soggy soil can be fatal and that in very cold winters the foliage might die back but the plant will send up new growth in spring. (Source: mymediterraneangarden.com)

BBC Gardeners’ World Magazine: “In very cold winters the foliage may shrivel but it quickly puts on new growth in spring.” Recommends it for growing outdoors year-round “in most parts of the UK, except the far north.” (Source: gardenersworld.com)

RHS (Royal Horticultural Society): describes the species as “hardy in average winters throughout much of the UK, except the far north” when given very sharp drainage, noting its origin as “an endemic of high-altitude habitats in South Africa.” (Source: rhs.org.uk)

Solliès-Toucas, Var, France (January 1985): during the severe cold wave of January 1985, which brought temperatures down to −15 °C (5 °F) across the Var department in Provence, established specimens of Aloiampelos striatula cultivated in Solliès-Toucas were killed to ground level but regrew from the base of the plants the following spring. This French report is significant because the Var (USDA zone 9b) normally experiences only occasional light frosts, and the January 1985 event was historically exceptional — the most severe cold episode in southern Provence since 1956. It confirms that the rootstock survival mechanism observed in England at −18 °C also operates in Mediterranean climates, even when the plants have not been acclimatised to regular hard frosts.

Summary of survival thresholds

Condition	Estimated threshold	Outcome
Well-drained soil, established plant	−6 to −9 °C (21 to 16 °F)	Above-ground growth undamaged
Well-drained soil, prolonged frost	−9 to −12 °C (16 to 10 °F)	Above-ground dieback, reliable resprout from stems
Well-drained soil, severe winter	−12 to −18 °C (10 to 0 °F)	Complete above-ground death, resprout from rootstock (documented)
Wet or poorly drained soil	−3 to −6 °C (27 to 21 °F)	Risk of fatal rot at root level

The distinctive cold-hardiness profile of Aloiampelos striatula differs fundamentally from that of rosette alooids like Aristaloe aristata. Where Aristaloe aristata survives cold by keeping its compact rosette intact (provided it is dry), Aloiampelos striatula adopts a “sacrifice and resprout” strategy: the above-ground shrubby growth is expendable, and the rootstock regenerates it in spring. This makes Aloiampelos striatula more tolerant of wet cold than Aristaloe aristata (its stems can handle moisture better than a tight rosette), but the visual impact of a winter dieback is much greater — the plant looks dead for several months before regrowing.

Practical recommendations

In USDA zone 9a and warmer with dry winters, Aloiampelos striatula is fully evergreen and needs no protection.

In USDA zones 8a–8b, plant against a south-facing wall, in well-drained soil, with gravel mulch. Expect some stem dieback in hard winters, with reliable regrowth in spring. A light horticultural fleece during the coldest nights will protect the above-ground growth in all but the severest winters.

In USDA zone 7b (with mulch, drainage and shelter), root survival is possible for established plants, but expect total above-ground dieback every winter. The plant will function as a “herbaceous” perennial rather than an evergreen shrub.

Hybrids involving Aloiampelos striatula

The exceptional cold hardiness of Aloiampelos striatula has made it a target for hybridisation programmes aimed at producing cold-tolerant alooids with more ornamental appeal. The species’ relatively plain appearance — dark, narrow leaves, a sprawling habit, and a tendency to look straggly without pruning — is its main aesthetic weakness. Breeders hope that crossing it with more visually striking species will combine striatula’s toughness with better form, colour or flower quality. Results so far are promising but still at an early stage.

Aloiampelos striatula x Aristaloe aristata

This is the most widely documented hybrid involving Aloiampelos striatula. It is listed in the RHS Plant Finder database under the cross formula Aloiampelos striatula x Aristaloe aristata (previously sold as Aloe aristata x striatula). On Dave’s Garden, a United Kingdom grower mentions having produced this cross, noting that the plants are intermediate in habit between the compact rosette of Aristaloe aristata and the shrubby, stemmed growth of Aloiampelos striatula. However, the same source cautions that the cold hardiness of the hybrid “is not yet known” — it remains unclear whether it inherits the rootstock resprouting ability of Aloiampelos striatula, the compact dry-cold tolerance of Aristaloe aristata, or some combination of both.

The cross is phylogenetically remarkable: Aloiampelos striatula belongs to the early-branching scrambling aloe clade, while Aristaloe aristata belongs to the Astroloba–Tulista clade. These are among the most divergent lineages within the Alooideae, yet they can still produce viable offspring — a testament to the relatively low reproductive barriers within the subfamily. (Sources: rhs.org.uk, davesgarden.com)

Aloe ‘Cosmo’ x Aloiampelos striatula

Aloe ‘Cosmo’ is itself a hybrid involving Aristaloe aristata parentage, valued for its compact form and reasonable cold tolerance. A Dutch grower (Arjan) on the Agaveville forum has produced and field-tested crosses of Aloe ‘Cosmo’ with both the standard form and the orange-flowered form of Aloiampelos striatula. During the winter of 2023–2024 in the Netherlands (zone 8b), he reported the following results at −5 to −6 °C (21 to 23 °F):

Aloe ‘Cosmo’ x Aloiampelos striatula (standard form): survived with rain cover; dead without rain cover. Aloe ‘Cosmo’ x Aloiampelos striatula (orange form): dead without rain cover.

These results suggest that the F1 hybrids inherit some cold hardiness from the Aloiampelos striatula parent but are significantly less frost-tolerant than either pure parent — consistent with the observation that hybrid vigour in cold tolerance does not always occur and that the tolerance mechanisms of the two parents (rootstock resprouting vs. compact rosette dry-hardiness) may not combine additively. The same grower notes that Aristaloe aristata seedlings also performed poorly in the same trial (only 4 of 23 survived), suggesting that the specific winter conditions — wet Dutch cold — are challenging for all alooids regardless of parentage. (Source: agaveville.org, “Opinion on a hardy hybrid” thread)

Aloiampelos striatula as a parent for cold-hardy tree aloe breeding

On Agaveville (threads “Cold hardy tree aloe hybrids?” and “Opinion on a hardy hybrid”), several experienced growers discuss the potential of Aloiampelos striatula as a starting parent for long-term breeding programmes aimed at producing cold-hardy tree aloes. The rationale is straightforward: Aloiampelos striatula is the only stemmed, shrubby alooid that demonstrably survives temperatures well below −10 °C. If it could be crossed with larger tree aloe species (Aloidendron dichotomum, Aloidendron barberae, Aloe ferox, Aloe marlothii), the resulting hybrids might combine tree-like stature with cold tolerance.

However, growers identify several practical challenges. The flowering seasons are poorly aligned: Aloiampelos striatula is a summer bloomer in the Northern Hemisphere, while most of the desirable tree aloe crossing partners bloom in winter. This makes hand-pollination difficult without stored pollen or manipulated photoperiods. The F1 hybrids from striatula crosses tend to inherit the narrow-leaved, scraggly growth habit of the striatula parent, which is aesthetically undesirable. Multiple generations of backcrossing to the more ornamental parent would likely be needed. Additionally, the cold-tolerance mechanism of Aloiampelos striatula (rootstock resprouting after above-ground dieback) may not be useful in a tree aloe, where the permanent woody trunk is the entire architectural point.

Despite these obstacles, the consensus on specialist forums is that Aloiampelos striatula remains the most promising starting point for any serious attempt at breeding cold-hardy shrubby or arborescent alooids. The project is inherently multi-generational — a minimum of five to ten years from first cross to cold-tested F2 or backcross offspring.

Named cultivar: ‘Burly’

Aloe striatula ‘Burly’ is a selection made by the Californian breeder John Bleck, occasionally seen in specialist nurseries. It is not a hybrid but a selected cultivar of the species itself, reportedly more compact and robust than typical seedling-grown plants. It has been observed at the Berkeley Botanical Garden (California). (Source: agaveville.org, smgrowers.com)

Authority links

POWO (Plants of the World Online, Kew): https://powo.science.kew.org/taxon/…

POWO — var. caesia: https://powo.science.kew.org/taxon/…

PlantZAfrica (SANBI) — genus Aloiampelos: https://pza.sanbi.org/…

GBIF: https://www.gbif.org/species/9287107

Wikipedia: https://en.wikipedia.org/wiki/Aloiampelos_striatula

RHS Plant Finder: https://www.rhs.org.uk/plants/…

Dave’s Garden: https://davesgarden.com/guides/pf/go/57960

World of Succulents: https://worldofsucculents.com/…

Plant Lust: https://plantlust.com/plants/4364/aloiampelos-striatula/

Tropical Britain: https://www.tropicalbritain.co.uk/aloe-striatula.html

Bibliography

Grace, O.M., Klopper, R.R., Smith, G.F., Crouch, N.R., Figueiredo, E., Rønsted, N. & van Wyk, A.E. (2013). A revised generic classification for Aloe (Xanthorrhoeaceae subfam. Asphodeloideae). Phytotaxa 76: 7–14.

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. (1936). Aloe striatula var. caesia. Flowering Plants of South Africa 16: t. 633.

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.

Klopper, R.R., Retief, E. & Smith, G.F. (2009). The genus Aloe L. (Asphodelaceae: Alooideae) in the Free State province of South Africa. Haseltonia 14: 41–52.

Bornman, H. & Hardy, D.S. (1971). Aloes of the South African Veld. Voortrekkerpers, Johannesburg.

Cousins, S.R. & Witkowski, E.T.F. (2012). African Aloe ecology: A review. Journal of Arid Environments 85: 1–17.