Aloe corallina
Introduction
The Kunene coral aloe is at once distinguished by its pendent rosettes of grey-green, unarmed leaves, and coral-red, tubular flowers, 32 mm long, in a lax, branched panicle, in winter. The leaves are drawn together in a mitre-shaped head, but become spreading during rain. Best for dry, semi-arid or desert gardens.
Fig. 1. The Kunene Coral Aloe (Aloe corallina), which has unarmed leaves (without marginal teeth), a direct result of its inaccessible habitat, safe from most grazers.
Description
Description
The plants are slow-growing, pendulous, with leaves in apical rosettes, solitary or dividing and forming small pendent clusters of up to 6 heads. Rosettes up to 600 mm in diameter in solitary specimens, on stems up to 700 mm long and up to 80 mm diameter. Roots up to 3 mm in diameter. The leaves are firm, in dense rosettes), drawn together in a mitre-shaped head during the dry season, lanceolate-acuminate, up to 500 × 110 mm, the surface leathery, grey-green and its margin entire to slightly denticulate. The leaf tip (apex) ends in a sharp point (acute).
Fig. 2. Three plants of the Kunene Coral aloe (Aloe corallina) growing on a steep dolomite cliff-face near Okakora Spring, northern Namibia (Left). The base of a stem of Aloe corallina growing out of a crevice in the cliff (Right).
The inflorescence is 600–700 mm long, branched in the distal half, with up to 13 racemes forming a loose panicle, rarely solitary. The stalk of the inflorescence (scape) curves upwards from the pendent rosettes. The elongated racemes are ascending, the flower stalks (pedicels) up to 12 mm long. The coral-red perianth is presented sub-pendulous, 32 × 7 mm. The oblong fruiting capsule follows fertilization, 10–14 × 5–7 mm. The seeds angular, 3 × 1.5 mm, dark brown. Flowering is mainly in winter (May to June, in the Southern Hemisphere).
Fig. 3. Aloe corallina in flower (L) and in fruith (R) in habitat near Okakora Spring, on the lower Kunene River Valley, northern Namibia.
Conservation Status
Status
Plants grow on difficult to reach, dolomite cliffs and there is no danger of habitat degradation and consequently this species is not endangered.
Distribution and habitat
Distribution description
Aloe corallina is only known from cliffs along the lower Kunene Valley on both sides of the river, in Angola and Namibia. Plants are often locally abundant, growing on all aspects but mainly on exposed north, east and west facing, sheer cliffs in the Kunene River Valley of northern Namibia and southern Angola, at an altitude of 400–1 200 m.
Fig. 4. The dolomite mountains in the lower Kunene River Valley in northern Namibia, habitat of Aloe corallina.
The geology consists of dark Proterozoic Namibian dolomite (Otavi Group, Damara Sequence). The dolomite substrate is dark and rough in texture, with many fissures and crevices. Temperatures in the Kunene Valley are high throughout the year (often above 30°C , especially in summer). Plants are firmly rooted in crevices and on ledges large enough to support the roots and stem clusters. Rainfall occurs mainly in summer, ranging from 75–150 mm per annum and as a result of thunder showers (convectional). The associated vegetation consists of Desert and Arid savanna and it grows with the following plant species: Ceraria longipedunculata, Ficus cordata, F. glumosa and F. ilicina, Kalanchoe laciniata and K. lanceolata, Coleus hereroensis, Adenium boehmianum and Sterculia africana.
Fig. 5. Two plants of the Kunene Coral Aloe (Aloe corallina) on a dolomite cliff near Okakora Spring, northern Kaokoveld in the Kunene Valley, growing with Adenium boehmianum.
Derivation of name and historical aspects
History
Aloe corallina was first documented by Otto Leistner and Bernard de Winter, from the Botanical Research Institute in Pretoria, on an expedition to the Kaokoveld in 1957 (Gunn & Codd 1981), but only named in 1979 by Inez Verdoorn in the Flowering plants of Africa. Plants can be seen in the succulent collection at Babylonstoren Farm as well as the Botanical Society Conservatory in the Kirstenbosch National Botanic Garden. The species name corallina pertains to its coral red flowers.
Aloe corallina comes closest to A. dewinteri, a solitary, larger, also cremnophilous species from the dolomite cliffs near Sesfontein and the adjacent Khowarib Poort. The latter has larger open almost acaulescent rosettes, inflorescences (summer flowering) that are branched low down and bicoloured flowers (yellow and red) and the leaves have slightly larger teeth. It is also related to A. kaokoensis, a larger robust species with open, spreading rosettes and large panicles, the latter only known from a granite substrate.
The habitat of plants of both Aloe dewinterii and A. corallina were investigated by the author on several occasions and photographs of A. corallina were taken on route to Otjiboronbongo near the Kunene River (Namibia).
Fig. 6. A number of plants of the Kunene Coral Aloe (Aloe corallina) growing on a dolomite cliff-face near Okakora Spring, northern Namibia.
Ecology
Ecology
Plants with medium-sized, caulescent clusters, occupying smaller to larger crevices and ledges. Aloe corallina is a slow grower and a long-lived perennial. Where within reach, stems and leaves are heavily grazed by the Kaoko Rock Rabbit (Procavia kaokoensis). The leaves are distinctly incurved, entire (unarmed), pendulous, grey-green, without a powdery bloom, margins reddish, long-lived, deciduous from the base. The grey colouring deflecting the rays of the sun.
The juvenile leaves are armed with brownish teeth of 1 × 1 mm (5–7 mm apart) but as the plant matures the teeth become smaller and sometimes disappear completely, suggesting a reduction in energy expenditure (production of teeth) but possibly also revealing the evolutionary history of its ancestor.
Fig. 7. Aloe corallina in flower in habitat near Okakora Spring, on the lower Kunene River Valley, northern Namibia.
The young inflorescence curving upwards as it matures, presents the racemes in the typical ascending position. The main pollinators are sunbirds. After pollination, the fruiting capsule matures, becoming ascending and releasing the small seeds, with gusts of wind scattering the light angular seeds on the cliff. The seed is about 3 × 1.5 mm, an ideal size for establishment in crevices. Seeds are dispersed in winter and autumn, ready for the summer rains. Germination occurs in about 14–21 days.
Aloe corallina is prolific from the base, forming drooping clusters. The stems root when finding a new crevice and fallen branches will also root when wedged in a suitable crevice. The continual renewal of shoots and rooting of stems in new crevices by extended stems represent a sufficient vegetative backup dispersal strategy for the harsh cliff-face environment.
Uses
Use
No medicinal or cultural uses have been recorded.
Fig. 8. The Kunene Coral Aloe (Aloe corallina) in flower at Kirstenbosch National Botanical Garden.
Growing Aloe corallina
Grow
Aloe corallina grows best in dry, semi-arid, bushveld or Desert gardens , and a habitat should be created where the plants can become pendent. It grows easily and is excellent for embankments, gabions or rockeries and also grows well in containers. It is best grown in regions where the rainfall is below 400 mm per annum. Grow in an open situation, in a well-drained, sunny position. It thrives in sandy to loamy soils derived from dolomite (alkaline).
Aloe corallina is a habitat specialist and not well-established in cultivation. Plants are slow growing and respond well to watering and feeding. Water can be given sparingly during summer but should be withheld during winter.
Plants can easily be propagated from basal offshoots or seeds. Sow seed in spring, summer or autumn in a sandy medium. First moisten the substrate with fine rose. Cover the seed lightly with a thin layer of sand. Keep moist and in a shady position. Germination is usually within 3 weeks and the young seedlings are relatively fast growing. Transplant seedlings to individual containers once large enough to handle. Flowering takes place in the fourth year.
In a region away from its native habitat it is best grown in a greenhouse where conditions can be adapted according to the plant’s needs. Here it performs at its best grown as a pot plant in a position that simulates the cliff environment. The soil should be sandy and slightly alkaline, with ample feeding during summer.
The plants are frost-sensitive and should be protected during the winter where frost can be a problem.
Plants are relatively disease free but snout weevils (Brachycercus monachus) may be a problem.
References
- Gunn, M. & Codd, L.E. 1980. Botanical exploration of southern Africa. Balkema, Cape town.
- Verdoorn, I.1979. Aloe corallina. Flowering Plants of Africa 45: t. 1788.
Credits
Ernst van Jaarsveld
Kirstenbosch National Botanical Garden (Retired 2015)
Babylonstoren Farm
Extraordinary senior lecturer and researcher,
Department of Biodiversity and Conservation, University of the Western Cape
September 2021
Plant Attributes:
Plant Type: Succulent
SA Distribution:
Soil type: Sandy, Loam
Flowering season: Winter
PH: Alkaline, Neutral
Flower colour: Red
Aspect: Full Sun
Gardening skill: Average
Special Features:
Attracts birds
Drought resistant
Feature plant
Good potplant
Horticultural zones
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