The quiver tree — Aloidendron dichotomum — may be the most photographed alooid on Earth. Its silhouette against a Namibian sunset, a forking crown of smooth, pale branches capped with rosettes of blue-green leaves, has become the defining image of the southern African desert. The San people hollowed out its branches to make quivers for their arrows. Climate scientists use its retreat as evidence of a warming world. It has appeared on South African banknotes, postage stamps and tourism posters for a century. And it is just one of six species of tree aloe — the genus Aloidendron.
These are the giants of the alooid world. Where most aloes form ground-hugging rosettes, the tree aloes build massive, forking, succulent trunks that can reach eighteen metres tall and live well over a hundred years. They are keystone species in desert and forest ecosystems — providing shelter, nesting sites and nectar for birds, insects and mammals. They are icons of arid southern Africa, from the scorching Richtersveld to the subtropical forests of KwaZulu-Natal.
The genus Aloidendron was separated from Aloe in 2013, recognising that tree aloes form their own evolutionary lineage within the alooid clade. This page is the reference for the genus on our site. It covers taxonomy, all six accepted species, the controversial seventh, conservation, cultivation and the resources that every tree aloe enthusiast needs.
Taxonomy and classification
Separation from Aloe
Tree aloes were long classified within Aloe, where they were placed in section Dracaloe (Berger 1908) and section Aloidendron (Reynolds 1950). They were always recognised as distinctive — their arborescent habit, forking (dichotomous) branching and deciduous lower leaves set them apart from all other aloes — but until molecular data became available, there was no formal consensus on whether these characters warranted a separate genus.
In 2013, Grace et al. proposed separating the tree aloes into the genus Aloidendron, based on molecular phylogenetic evidence showing that they form a monophyletic clade distinct from Aloe sensu stricto. The genus was formally established by Klopper and Smith, with six species transferred from Aloe. Manning et al. (2014) confirmed the circumscription, and Woudstra et al. (2025) validated the monophyly of the genus using nuclear phylogenomics.
The genus name combines Aloe with the Greek dendron (“tree”) — literally, “tree aloe.”
Position in the alooid group
Aloidendron belongs to the family Asphodelaceae, subfamily Asphodeloideae, within the alooid clade. Molecular studies place it within the “true aloe” clade — closer to Aloe sensu stricto and Aloiampelos (the rambling aloes) than to the haworthioid genera (Haworthia, Haworthiopsis, Gasteria, Tulista, Astroloba). Its exact sister relationship within this clade is not yet fully resolved — some analyses place it sister to Aloe section Kumara (now the separate genus Kumara, containing the fan aloe Kumara plicatilis), but this requires further phylogenomic confirmation.
The dichotomous branching character
The defining morphological character of Aloidendron is dichotomous branching — the growing tip of each branch divides into two equal forks, producing the symmetrical, candelabra-like crown architecture that is so striking in the quiver tree and other species. This branching pattern is shared with Kumara plicatilis (the fan aloe), but in Kumara the leaves remain in two opposite ranks (distichous), whereas in Aloidendron they are arranged in rosettes. The lower leaves are deciduous — they dry and fall away as the stem elongates, leaving a clean, smooth trunk.
How many species? The controversy
The genus contains six widely accepted species. A seventh — Aloidendron sabaeum, from Saudi Arabia and Yemen — was transferred to Aloidendron by Manning et al. (2014) following Reynolds’ grouping of this species with the eastern tree aloes. However, molecular studies by Malakasi et al. (2019) found that A. sabaeum is nested within Aloe, not within Aloidendron — its transfer was based on an erroneous height record (reported as nine metres; in reality only three metres). The original concept of Grace et al. (2013) excluded A. sabaeum, and this exclusion is supported by the molecular evidence. The species is discussed below but not counted among the core six.
A separate question concerns the Malagasy species Aloe suzannae. Smith and Molteno (2019) proposed a monotypic genus Aloestrela for this remarkable succulent tree of southern Madagascar. However, Malakasi et al. (2019) found A. suzannae to be sister to Aloidendron eminens (from Somalia), firmly within the Aloidendron clade. Its inclusion in the genus would raise the species count to seven and extend the geographic range to Madagascar — but a comprehensive taxonomic revision has not yet been published.
Distribution
Aloidendron is a genus of southern and eastern Africa, with one outlier in the Horn of Africa. The six species can be divided geographically into two groups that correspond to the two clades recovered in molecular phylogenies:
The southwestern desert clade: Aloidendron dichotomum, Aloidendron pillansii, Aloidendron ramosissimum — arid desert and dry shrubland in the Richtersveld (South Africa/Namibia border region) and the Northern Cape. These species grow in the driest, most extreme habitats of any alooids — rainfall less than 200 mm per year, temperatures exceeding 45 °C.
The eastern forest/thicket clade: Aloidendron barberae, Aloidendron tongaense, Aloidendron eminens — subtropical coastal forests and thickets from the Eastern Cape through KwaZulu-Natal to Mozambique and Somalia. These species grow in far wetter conditions — rainfall over 1 000 mm per year in some localities — and in partial shade under a forest canopy.
This geographic and ecological split is one of the most interesting features of the genus: the western species are adapted to extreme desert, the eastern species to humid forest. Malakasi et al. (2019) showed that this ecological divergence does not correspond to two separate evolutionary lineages within the genus — instead, the two clades correspond to geography, not habitat, suggesting that the transition between desert and forest preferences occurred multiple times.
Morphology: succulent giants
Growth form: arborescent — the only aloe relatives that are true trees. Stems are succulent, with a soft, fibrous interior (not woody in the conventional sense) and a smooth, often flaking bark. The branching is dichotomous (forking), producing a symmetrical, candelabra-like crown. The lower leaves are deciduous, leaving a clean trunk.
Size: the largest alooids by a very wide margin. Aloidendron barberae, the largest species, reaches fifteen to eighteen metres tall with a trunk diameter approaching one metre at the base — a specimen planted at Kirstenbosch Botanical Garden in 1922 had grown to a basal diameter of three metres by 2011. Aloidendron pillansii reaches ten to twelve metres. Aloidendron dichotomum reaches seven to nine metres. At the other extreme, Aloidendron ramosissimum is a shrubby species rarely exceeding two to three metres.
Leaves: succulent, arranged in rosettes at the branch tips. Typically long, narrow, channelled on the upper surface, with toothed margins. Colour ranges from bright green (A. barberae) to blue-grey with a glaucous bloom (A. dichotomum). Leaves are deciduous from below — as the stem elongates, the lower leaves dry and fall, exposing the trunk.
Flowers: borne in branched inflorescences (panicles) at the branch tips. Two distinct flower types: the western desert species have short, ventricose (swollen in the middle) yellow flowers pollinated by short-billed birds (weavers, starlings, white-eyes); the eastern forest species have longer, curved, pendant pink to orange flowers pollinated by sunbirds.
Lifespan: tree aloes are among the longest-lived succulents. A specific quiver tree (A. dichotomum) was estimated to be between one hundred and one hundred and forty-five years old. Aloidendron pillansii may live even longer.
Species list: the six accepted species
The southwestern desert species
Aloidendron dichotomum (Masson) Klopper & Gideon F. Sm. (syn. Aloe dichotoma) — Northern Cape (South Africa) and Namibia. The quiver tree (kokerboom in Afrikaans). The most iconic and widely known tree aloe — and arguably the most iconic succulent in Africa. A tree of seven to nine metres tall with a smooth, pale trunk covered in flaking bark, dichotomously branching into a rounded, symmetrical crown. Rosettes of blue-grey, glaucous leaves with finely toothed margins. Yellow flowers in branched inflorescences in late autumn to winter, pollinated by weavers and starlings. Extremely drought-tolerant — grows in areas with less than 200 mm of annual rainfall. The fibrous, lightweight trunk was traditionally hollowed out by the San people to make quivers for their arrows — the origin of the common name. Individual trees can live well over a century. This species is a flagship for climate change research — studies have documented the retraction of quiver tree populations from their northern (hotter) range limit, with models predicting significant range contraction over the coming decades. Conservation: Vulnerable (VU) — threatened by climate change, habitat degradation, livestock trampling seedlings and illegal harvesting.
Aloidendron pillansii (L. Guthrie) Klopper & Gideon F. Sm. (syn. Aloe pillansii) — Richtersveld (South Africa/Namibia border). The giant quiver tree or bastard quiver tree. One of the rarest and most endangered tree aloes — fewer than nine thousand individuals remain in the wild. A massive, slow-growing tree reaching ten to twelve metres, with a thick trunk and a less symmetrical crown than A. dichotomum. The branches tend to point upward and outward rather than forming the rounded canopy of the quiver tree. Uniquely among Aloidendron, A. pillansii flowers in spring (October in the southern hemisphere) rather than in late autumn/winter. It has an unusual association with heavy metal soils in Namibia — acting as an indicator species. Conservation: Endangered (EN), assessed as Critically Endangered by some authorities — threatened by climate change, extremely slow growth and virtually no seedling recruitment in many populations.
Aloidendron ramosissimum (Pillans) Klopper & Gideon F. Sm. (syn. Aloe ramosissima, Aloe dichotoma subsp. ramosissima) — Richtersveld (SW Namibia to Northern Cape). The maiden’s quiver tree. The smallest and most shrubby of the tree aloes — rarely exceeding two to three metres, often multi-stemmed from the base, with many branches giving a densely twiggy appearance (hence ramosissimum, “most branching”). Some authorities have treated it as a subspecies of A. dichotomum, but molecular and morphological evidence supports its recognition as a distinct species. Flowers yellow. Conservation: Vulnerable (VU).
The eastern forest species
Aloidendron barberae (Dyer) Klopper & Gideon F. Sm. (syn. Aloe barberae, Aloe bainesii) — widespread from the Eastern Cape through KwaZulu-Natal, Eswatini and Mpumalanga to Mozambique and East Africa. The eastern tree aloe. Africa’s largest aloe — reaching fifteen to eighteen metres tall with a trunk diameter of nearly one metre. Named for Mary Elizabeth Barber (1818–1899), a naturalist, writer, painter and plant collector in the Eastern Cape. The species was independently collected by Thomas Baines in 1873 and named Aloe bainesii — but barberae has nomenclatural priority. A striking sculptural tree with smooth grey bark, a rounded crown and dark green, recurved leaves. Flowers are salmon-pink with green-tipped buds, appearing in winter, often hidden among the leaves. Pollinated by weavers and white-eyes. Grows in subtropical coastal forests, kloofs and dry river valleys — requires at least 1 000 mm of annual rainfall and mild, nearly frost-free conditions. Readily propagated from large stem cuttings (truncheons) as well as seed. Several popular hybrids exist: ‘Hercules’ (A. barberae × A. dichotomum), ‘Goliath’ (A. barberae × Aloe vaombe). Conservation: Least Concern (LC).
Aloidendron tongaense (van Jaarsv.) van Jaarsv. (syn. Aloe tongaensis) — Tongaland (northern KwaZulu-Natal) and southern coastal Mozambique. Described as recently as 2010 by Ernst van Jaarsveld — previously known as a coastal form of A. barberae or sold under the horticultural name Aloe ‘Medusa’. A much-branched tree to eight metres with a rounded crown, pale green, rubbery leaves (often taking on an orange hue in cool weather) and distinctive yellowish-orange curved flowers borne on candelabra-like inflorescences that rise above the foliage — a clear diagnostic difference from A. barberae, whose inflorescences are tucked within the leaf rosettes. Grows in sand forest at very low altitude (five to thirty metres above sea level) in warm, humid, subtropical conditions. One of the most frost-sensitive alooids — damaged below -2 °C. Conservation: Least Concern (LC).
Aloidendron eminens (Reynolds & P.R.O. Bally) Klopper & Gideon F. Sm. (syn. Aloe eminens) — Somalia. The only Aloidendron species in East Africa, and one of the least known. A tree of five to eight metres with curved, pendant, orange flowers. Grows in dry deciduous woodland and on rocky slopes. Very rarely cultivated outside botanic gardens. Conservation: Endangered (EN) on the IUCN Red List — threatened by habitat degradation in Somalia.
The controversial species
Aloidendron sabaeum (Schweinf.) Boatwr. & J.C. Manning (syn. Aloe sabaea) — Saudi Arabia and Yemen. A small tree to three metres (not nine metres as erroneously reported by Reynolds 1966 — a misrecording that led to its grouping with the true tree aloes). Molecular evidence (Malakasi et al. 2019) places this species within Aloe, not within Aloidendron — its transfer was based on incorrect height data. The original Grace et al. (2013) concept of Aloidendron excluded it. A taxonomic revision returning it to Aloe is expected. It is listed here for completeness, as some references still include it, but it is not considered a member of Aloidendron in the current molecular consensus.
Cultivation: patience and space
Tree aloes are surprisingly easy to grow — but they need two things that most succulents do not: patience (they are long-lived trees that grow on a timescale of decades) and space (even the smallest species, A. ramosissimum, reaches two to three metres).
Light: full sun for the western desert species (A. dichotomum, A. pillansii, A. ramosissimum). Partial shade to full sun for the eastern forest species (A. barberae, A. tongaense), which in habitat grow as understorey trees or in dappled forest light.
Substrate: well-drained, mineral-rich. In-ground planting is preferred for long-term growth — tree aloes develop extensive root systems. For container growing (young plants only), use a very gritty, fast-draining mix. The western species prefer lean, sandy soils; the eastern species tolerate richer, loamier soil with more organic matter.
Watering: all species are extremely drought-tolerant once established. The western desert species are adapted to less than 200 mm of annual rainfall — in cultivation, water sparingly and allow the soil to dry completely between waterings. The eastern species tolerate and appreciate more regular watering, especially during the growing season — they originate from areas with over 1 000 mm of annual rainfall.
Temperature: a critical distinction. The western species tolerate more cold — A. dichotomum withstands brief frost to approximately -5 to -7 °C in dry conditions, making it the hardiest tree aloe and a realistic prospect for sheltered gardens in USDA zone 9 and mild parts of zone 8b. Aloidendron pillansii and A. ramosissimum are slightly less hardy. The eastern species are frost-sensitive: A. barberae tolerates brief frost to approximately -2 to -3 °C but is damaged below this; A. tongaense is damaged below -2 °C and killed below approximately -6 °C. In frost-prone climates, the eastern species must be grown in containers and overwintered indoors or in a heated greenhouse.
Growth rate: variable. Aloidendron barberae is relatively fast-growing for a tree aloe — a well-watered specimen in a mild climate can add thirty to fifty centimetres of height per year. Aloidendron dichotomum is moderate. Aloidendron pillansii and A. tongaense are slow. In all cases, these are plants that mature over decades, not years.
Container growing
Young tree aloes adapt well to large containers and can be grown as striking architectural specimens for many years before requiring in-ground planting. All species are excellent as conservatory or patio plants in frost-prone climates. However, container culture limits ultimate size — a tree aloe will never reach its full stature in a pot.
Propagation
From seed: the standard method for all species. Germination is reliable at 20–25 °C and usually occurs within three weeks. Seedlings are relatively fast-growing (for succulents) and can be planted out within a year.
From stem cuttings (truncheons): highly effective for the eastern species — A. barberae and A. tongaense root readily from large stem cuttings taken during the warmer months. Allow the cut surface to dry and callous before planting. This method allows rapid establishment of large specimens. Not effective for A. dichotomum and A. pillansii, which do not root from cuttings.
Conservation: icons under threat
Tree aloes are among the most conservation-significant succulent plants in Africa. Their large size, long lifespan and slow reproduction make them highly vulnerable to environmental change.
Aloidendron pillansii is the most threatened species — fewer than nine thousand individuals remain in the wild, and virtually no seedling recruitment has been observed in many populations. The species is listed as Endangered (some authorities say Critically Endangered). Climate change, livestock trampling seedlings and the species’ extremely slow growth rate are the main threats.
Aloidendron dichotomum has become a flagship species for climate change impacts on southern African biodiversity. Long-term studies have documented the retraction of quiver tree populations from their northern (hotter, drier) range limit. Models predict significant range contraction — the quiver tree forests of the northern Richtersveld and Namibia may disappear within decades if warming continues. The species is listed as Vulnerable.
All Aloidendron species are listed under CITES Appendix II. The southwestern species (A. dichotomum, A. pillansii, A. ramosissimum) face additional threats from illegal harvesting — mature quiver trees are valuable in the landscaping trade, and some populations have been depleted by the removal of large specimens.
Traditional uses
The fibrous, lightweight wood of Aloidendron dichotomum has been used by the Khoi-San people for centuries — hollowed-out branches served as quivers for arrows (the origin of the name “quiver tree” / kokerboom), and the light trunk wood was used to construct cool rooms and small shelters in Namaqualand. In northern KwaZulu-Natal, A. barberae is traditionally left standing when forests are cleared — local belief holds that tree aloes protect against evil spirits and serve as lightning conductors. The succulent nature of tree aloes has also led to their use as fire barriers around homesteads in fire-prone areas.
Web resources
Plants of the World Online (POWO) — Kew Royal Botanic Gardens. The authoritative database for accepted names and synonymy. Search “Aloidendron” for all accepted species. powo.science.kew.org
PlantZAfrica — South African National Biodiversity Institute (SANBI). Excellent genus page and individual species pages for all southern African species: A. dichotomum, A. pillansii, A. ramosissimum, A. barberae, A. tongaense. Distribution data, ecology, cultivation advice, conservation status. pza.sanbi.org
The Ruth Bancroft Garden (ruthbancroftgarden.org). Based in California — excellent cultivation notes for tree aloes in Mediterranean climates.
Garden Aloes (gardenaloes.com). Practical guides to growing tree aloes with a focus on landscaping applications.
iNaturalist (inaturalist.org). Citizen-science observations with photographs and GPS data. Particularly valuable for understanding the distribution of A. dichotomum across Namibia and the Northern Cape.
Bibliography
Taxonomy and phylogenetics
Grace O.M., Klopper R.R., Figueiredo E., Smith G.F. (2013). A revised generic classification for Aloe (Xanthorrhoeaceae subfam. Asphodeloideae). Phytotaxa, 76: 7–14. — The paper that established Aloidendron as a genus, transferring six species from Aloe.
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. Systematic Botany, 39(1): 55–74. — Confirmed the circumscription of Aloidendron and transferred A. sabaeum to the genus.
Malakasi P., Bellot S., Leitch I.J., Grace O.M. (2019). Museomics clarifies the classification of Aloidendron (Asphodelaceae), the iconic African tree aloes. Frontiers in Plant Science, 10: 1227. — Sequenced chloroplast genomes and ITS from herbarium specimens. Key findings: A. sabaeum is nested within Aloe (not Aloidendron); A. suzannae (Madagascar) is sister to A. eminens within the Aloidendron clade; the genus comprises two geographic clades (southwestern desert vs. eastern forest).
Smith G.F., Molteno S. (2019). A new generic name for the Madagascan tree aloe Aloe suzannae. Haseltonia, 26: 95–99. — Proposed the monotypic genus Aloestrela for A. suzannae — not supported by the molecular data of Malakasi et al. (2019).
Woudstra Y., Grace O.M., Klopper R.R. et al. (2025). Nuclear phylogenomics reveals strong geographic patterns in the evolutionary history of Aloe and related genera (alooids). Annals of Botany. — Confirms the monophyly of Aloidendron using nuclear genome data.
Species descriptions and ecology
Van Jaarsveld E.J. (2010). Aloe tongaensis, a new species from Tongaland, KwaZulu-Natal. Aloe, 47(3): 64–71. — The description of the most recently recognised species.
Van Jaarsveld E.J., Judd D. (2015). Tree aloes of Africa. — A comprehensive treatment of arborescent aloes including ecology, distribution and cultivation.
Foden W. et al. (2007). A changing climate is eroding the geographical range of the Namib Desert tree aloe through population declines and dispersal lags. Diversity and Distributions, 13: 645–653. — The landmark study on climate-driven range retraction in A. dichotomum.
General references
Reynolds G.W. (1950). The Aloes of South Africa. — The classic monograph, describing tree aloes within Aloe sections Dracaloe and Aloidendron.
Carter S., Lavranos J.J., Newton L.E., Walker C.C. (2011). Aloes: The Definitive Guide. Kew Publishing. — The most comprehensive modern reference for all aloe-related genera.
Going further
The genus Aloidendron is small — six species — but its members are among the most iconic, most photographed and most conservation-significant succulents on Earth. The quiver tree is a symbol of the Richtersveld, of the Namib, of southern African natural heritage itself. The eastern tree aloe is Africa’s largest alooid — a living sculpture that takes a century to build. And the giant quiver tree is one of the most endangered plants on the continent, with fewer than nine thousand individuals left in the wild. Growing a tree aloe is a commitment measured in decades — but the reward is a living monument, a piece of evolutionary history in your garden. Our site offers species profiles, care guides and conservation information for every alooid genus.