Aloe vacillans

Overview

Aloe vacillans is recorded from Yemen and Saudi Arabia. It is stemless or short-stemmed, with stems sometimes erect or decumbent, and its flowers are recorded as red, reddish-pink or yellow. [1, 2, 3]

Classification and nomenclature

Accepted name: Aloe vacillans Forssk. [3]
Protologue bibliography: Forssk., Flora Aegyptiaco-Arabica: 74 (1775). [1, 2, 3]
Type locality and type material: Yemen, Kurmah (Kusmah), 14°35'N, 43°39'E; Forsskål s.n.; C†. [1]
Synonyms: Aloe audhalica Lavranos & D.S.Hardy [1, 4, 3]

Aloe dhalensis Lavranos [1, 4, 3]

Etymology

Interpretations of the epithet differ: one interprets Latin vacillans as “variable” in reference to flower-colour variation; another probably relates it to “swinging to and fro” and the decumbent habit. [1, 4]

Key characteristics

Growth form

Stemless or short-stemmed; where stems are present they may be erect or decumbent. Plants may be solitary or offsetting into groups. [1, 2]

Leaves

Leaves are erect and lanceolate, 30–60 cm long and 7–13 cm wide, and are described as glaucous-grey or glaucous green. [1, 2]

Leaf surface and margin

The upper surface is flat low down and slightly canaliculate toward the acute apex, while the lower surface is convex. The margins bear sharp brown triangular teeth 2–3 mm long and 5–10 mm apart. [1, 2]

Inflorescence and flowers

Inflorescences are erect, simple or branched with up to five branches. Racemes are described as cylindrical-acuminate or elongate-conical; flowers are recorded as red, reddish-pink, or yellow, with the perianth about 30 mm long. [1, 2]

Distribution

Yemen and Saudi Arabia. Widely recorded in western and southwestern Yemen and in southern Asir Province, Saudi Arabia. [1, 2, 3]

Habitat

Steep mountain slopes, cliff ledges, degraded open scrub forest and grasslands, on volcanic or metamorphic rock, at 1,300–3,000 m. [1, 2]

Main references

McCoy, T. (2019). The Aloes of Arabia. McCoy Publishing, Temecula, California. pp. 131–133.
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes: The Definitive Guide. Royal Botanic Gardens, Kew. p. 367.
Royal Botanic Gardens, Kew. Plants of the World Online: Aloe vacillans Forssk. (accessed 2026-09-22). Source
Grace, O.M., Klopper, R.R., Figueiredo, E. & Smith, G.F. (2011). The Aloe Names Book. Strelitzia 28. South African National Biodiversity Institute, Pretoria. pp. 156–157.

Updates

Classification, distribution and descriptive information are revised as new sources are verified or taxonomic treatments change.