Aloe porphyrostachys subsp. porphyrostachys

Overview

Aloe porphyrostachys subsp. porphyrostachys is a densely clumping, essentially stemless aloe of high rocky sites in Saudi Arabia, with blue-grey leaves that may become purplish-grey in dry periods. Its tall, much-branched inflorescences bear very dense, elongate cylindrical racemes with red to orange flowers held close to the axis. [1] [2]

Key characteristics

Growth form

Essentially stemless or with only a short decumbent stem, offsetting from the base to form dense groups. [1] [2]

Leaves

Leaves are erect to spreading, narrow and tapering, smooth, blue-grey and sometimes purplish-grey during dry periods. [1] [2]

Leaf margin

The white cartilaginous margin bears firm, sharp triangular teeth that are relatively widely spaced. [1] [2]

Inflorescence

Inflorescences are erect and strongly branched; the racemes are elongate-cylindrical and very densely flowered. [1] [2]

Flowers

Flowers are orange to red, with a cylindrical to clavate, three-angled perianth; the stamens and style are conspicuously exserted. [1] [2]

Exudate

The exudate is yellow when fresh and dries light brown. [1] [2]

Distribution

Saudi Arabia [3]

Habitat

It grows mainly on granitoid rocks and rocky slopes or flatter ground near high mountain summits, in an extremely dry winter-rainfall climate. [1] [2]

Flowering

Flowering is in spring, usually from April to May. [1]

Relationships

Carter et al. (2011) relates it to A. rubroviolacea, A. pseudorubroviolacea and A. schoelleri. These taxa share dense racemes and strongly exserted reproductive organs, while A. porphyrostachys is distinguished by narrower leaves with more closely set marginal teeth. [2]

WCVP accepts A. porphyrostachys subsp. koenenii as a separate sibling subspecies. Carter et al. (2011) describes the nominotypical A. porphyrostachys as the larger plant, with longer, less rigid leaves, more inflorescence branches, and longer racemes, floral bracts and flowers. [2] [3]

Population and conservation

McCoy (2019) describes natural populations as stable with seedling regeneration, but notes that overall numbers are not large and could be strongly affected by environmental pressure. [1]

Classification and nomenclature

Classification: Accepted as Aloe porphyrostachys subsp. porphyrostachys, the nominotypical subspecies of A. porphyrostachys. WCVP separately accepts subsp. koenenii. [3]
Etymology: The name porphyrostachys derives from Greek words referring to purple or purplish-red and a spike, in reference to the red, densely flowered inflorescences. [4] [1]

Parent taxon: Aloe porphyrostachys
Sibling subspecies: Aloe porphyrostachys subsp. koenenii

References

McCoy, T. (2019). The Aloes of Arabia. McCoy Publishing, Temecula, California. pp. 297–301, 303.
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes: The Definitive Guide. Royal Botanic Gardens, Kew. pp. 448–449, 455.
World Checklist of Vascular Plants (WCVP).
Grace, O.M., Klopper, R.R., Figueiredo, E. & Smith, G.F. (2011). The Aloe Names Book. Strelitzia 28. South African National Biodiversity Institute, Pretoria. p. 125.