Aloe sabaea — the Yemen tree aloe — is one of the very few tall aloes native to the Arabian Peninsula: a slender, single-headed plant with a crown of long, drooping pale green leaves and open, multi-branched spikes of coral-red flowers. Native to the mountains of south-western Saudi Arabia and Yemen, it was for several years treated as the seventh species of the genus Aloidendron under the name Aloidendron sabaeum. A 2019 study returned it to Aloe in the strict sense, and that is how Plants of the World Online now treats it. This article covers its taxonomy and synonymy, range, morphology and cultivation.
Taxonomy and nomenclature
Aloe sabaea was described by the German botanist and explorer Georg August Schweinfurth in 1894 (Bulletin de l’Herbier Boissier 2, appendix 2: 74), from material he collected in Yemen at Agara, near Hodjela, on 1 February 1889. The epithet refers to Sabaea, the Roman name for the south-western Arabian region now corresponding to Yemen.
In 1962 Gilbert Westacott Reynolds described a second name, Aloe gillilandii, from a plant given to him in 1952 by H.B. Gilliland, who had collected it on the Dathina Plain, about 130 miles north-east of Aden. It is now a heterotypic synonym of Aloe sabaea.
The 2013 generic revision of Aloe created Aloidendron for the tree aloes. In their 2014 phylogeny of the Alooideae, Manning and colleagues moved Aloe sabaea into that genus as Aloidendron sabaeum (Systematic Botany 39: 67). In 2019 Smith, Klopper and Grace published a paper titled “Aloidendron consists of six species, not seven: Aloe sabaea is a true aloe” (Phytotaxa 416: 88–90), restoring the original name. POWO follows this treatment and accepts Aloe sabaea, while some older databases and reference works still list Aloidendron sabaeum.
Synonyms: Aloidendron sabaeum (Schweinf.) Boatwr. & J.C.Manning (2014); Aloe gillilandii Reynolds (1962).
Why it is not an Aloidendron
Despite its tree-like habit, Aloe sabaea has no close relative among the true Aloidendron species such as A. dichotomum or A. barberae. Its apparent closest relatives are two tall East African aloes, Aloe ballyi and Aloe elata. Like them, it has a tall slender stem, a multi-branched inflorescence and toxic sap with a smell compared to rat urine. Leaving it in Aloidendron would have separated it from these relatives and made the genus non-monophyletic.
Distribution and habitat
Aloe sabaea is native to Saudi Arabia and Yemen. Its range follows the mountain chain parallel to the Red Sea, from south-western Saudi Arabia southwards through western Yemen, with an outlying population in the Hadhramaut region of eastern Yemen. It grows on dry rocky hillsides and stony, barren slopes between about 300 and 2,000 m, in a climate with 150 to 700 mm of annual rainfall. At the upper end of its altitude range it occasionally experiences winter frost.
Description
Habit. A single-headed plant with a slender stem, normally reaching 3 to 4 m in height. The head carries relatively few leaves (sometimes only six to eight in wild plants), which gives the plant a top-heavy, sparse look quite unlike the dense crowns of the tree aloes of southern Africa.
Leaves. Long, tapering, light green and succulent, 65 to 100 cm long and 8 to 14 cm wide at the base, shallowly channelled rather than flat. A narrow white to pinkish translucent border runs along most of the margin, with small white teeth at irregular intervals. In some populations the leaves arch outwards, in others they bend near the base and hang down alongside the stem. Dead leaves are shed, so the stem is not covered by a skirt of dry leaves.
Inflorescence and flowers. The inflorescence is multi-branched and up to about 1 m tall; each branch ends in an open, conical or rounded-conical raceme. The tubular flowers are coral-red to red-orange and turn yellow at the mouth as they age. The perianth is up to about 26 mm long and 8 to 10 mm across, with slightly spreading to recurved tips from which the six stamens and the pistil protrude. Young plants carry only a few branches; large old plants may bear dozens.
Flowering period. In its native range, flowering peaks in November and December. In California cultivation it is later, from late January or February to March or April.
Fruit and seed. The glossy green, oval capsule is 20 to 24 mm long and 10 to 12 mm wide, with three shallow grooves marking the chambers. When dry it splits along the grooves. The seeds are dark, three-angled and 4 to 5 mm long, surrounded by short grey papery wings.
Similar species
Among the Arabian aloes, Aloe sabaea most resembles Aloe rivierei, rather like a taller, non-suckering version of it, although the resemblance is only superficial. It differs from the true tree aloes of Aloidendron in its slender stem, sparse head of leaves, open red-orange inflorescence and dry mountain habitat, as opposed to the thick trunks, dense crowns and pink or yellow flowers of the African species.
Cultivation
Aloe sabaea is a striking garden plant for dry, mild-winter climates, hardy in USDA zones 9 to 11.
Light and soil. Full sun and excellent drainage. Excess moisture is the main danger and leads to root rot.
Cold. Established plants in cultivation have survived overnight lows down to about −3 °C, but not extended periods below freezing. This is comparable to Aloidendron barberae and clearly less than the hardiest tree aloes. In wet-winter climates, keep it dry and sheltered.
Propagation. By seed. Germination is good, but seedlings may damp off if overwatered; a free-draining mineral mix with a top layer of fine gravel helps.
Authority links
POWO (Kew): https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:529862-1
IPNI, Aloe sabaea: https://www.ipni.org/n/529862-1
IPNI, Aloidendron sabaeum: https://www.ipni.org/n/77142507-1
Ruth Bancroft Garden, plant highlight: https://www.ruthbancroftgarden.org/plants/aloe-sabaea/
Bibliography
Schweinfurth, G. (1894). Aloe sabaea. Bulletin de l’Herbier Boissier 2(App. 2): 74.
Reynolds, G.W. (1962). Aloe gillilandii. Journal of South African Botany 28: 287.
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.
Smith, G.F., Klopper, R.R. & Grace, O.M. (2019). Aloidendron (Asphodelaceae subfam. Alooideae) consists of six species, not seven: Aloe sabaea is a true aloe. Phytotaxa 416(1): 88–90. DOI: 10.11646/phytotaxa.416.1.11
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes. The definitive guide. Kew Publishing, Royal Botanic Gardens, Kew.
Wood, J.R.I. (1997). A Handbook of the Yemen Flora. Royal Botanic Gardens, Kew.
Kemble, B. (2026). Plant Highlight: Aloe sabaea. Ruth Bancroft Garden.