Aloe catengiana, known from the southern Angolan highlands, has recently been found in the Omavanda area of the Baynes Mountains in northern Kaokoveld, Namibia. It is a much branched shrubby aloe with spreading, leafy branches up to about 1 m long. It thrives in cultivation and flowers during autumn.
Aloe catengiana is a fast-growing dwarf succulent with subterranean suckers, forming small, dense rosettes up to 200 mm in diameter. It has fleshy roots. The branches, each bearing 4-7 rosettes, become drooping on the cliff face. Its leaves are soft, very fleshy, oblong-triangular, about 100-200 x 8-10 mm, curving downwards and pendent from rock faces, becoming channelled and less succulent during the dry season. The leaf surface is smooth, slightly pale bluish green and white-spotted at the base. The leaf margins are minutely toothed (serrate), and slightly transparent (window), the teeth are soft and small and the leaf tip (apex) is pointed and armed with 5 or 6 teeth. The inflorescence is a slender panicle composed of several short racemes each bearing up to 15 flowers. The flower buds are orange; the open flowers are tubular, drooping to pendent, 25 mm long, bright orange-red, and yellow- and green-tipped. The perianth segments are free to the base. Its stamens are yellowish and 20-22 mm long. The ovary is oblong, 5-6 x 2 mm, grooved, brownish green with a style 18 mm long. Its capsules are 6 x 5 mm and the s eed s are oblong, angular, 3-4 x 1.5 mmand grey-black. Flowering occurs mainly during autumn (April, May in the southern hemisphere).
Aloe catengiana is rare in Namibia, but widespread and fairly common on the highlands of southern Angola. In the Omavanda it is confined to east-facing cliffs. Due to its safe cliff habitat it is not threatened.
Distribution and habitat
Aloe catengiana is known only from the upper, east-facing, quartzitic sandstone cliffs along the eastern part of the Omavanda (eastern Baynes Mountains) in Namibia. It grows at an altitude of 1 700-1 900 m. It also occurs at Catengue in the southern Angolan highlands and, according to Reynolds (1966), about 60 miles southeast of Benguella (alt. 600 m). At Omavanda, Namibia, plants occur scattered in sandstone rock crevices among savanna vegetation and are difficult to reach.
The soil is poor in minerals and acidic. Rainfall in the Kaokoveld habitat ranges from 300-400 mm per annum, and is experienced mainly in summer (in the form of thunder showers). Vegetation of the region includes savanna with bushwillows (Combretum zeyheri, C. apiculatum) and corkwood (Commiphora species) prominent. Aloe catengiana shares its habitat with other succulent plants such as Cotyledon orbiculata var. orbiculata, Cyphostemma currorii, Crassula transvaalensis, Kalanchoe lanceolata, Sarcostemma viminale, Tetradenia kaokoensis and Aeollanthus rehmannii.
Derivation of name and historical aspects
Aloe catengiana was named by Dr Gilbert Reynolds in the botanical journal Kirkia in 1960 ( Kirkia 1: 160; 1961). It was named for Catengue railway station, in the southern highlands (S.Angola), the place where this species was discovered by Dr Gilbert Reynolds and Dr Neil Smuts during an expedition to Angola in 1959 (Gunn & Codd 1981). In July 2004, Wessel Swanepoel, Steven Cars and the author came across this species on the eastern cliff face of the Baynes Mountains in Namibia.
Aloe catengiana is one of some 29 species of Aloe indigenous to Namibia (Rothmann 2004). It is one of 5 Namibian species of Aloe which are confined to cliffs. Other Namibian cliff-dwelling aloes include A. corallina, A. dewinter i, A. omavandae and A. meyeri. Aloe catengiana has a pendent habit on cliffs, but it is spreading when planted in containers. A. catengiana is at once distinguished from the four other cliff-dwelling species by its shrubby, much branched habit. Being the only shrubby Namibian species, it cannot be confused with any other aloe from that country. It is closely related to A. palmifrons, a much taller species (also branched) with larger teeth and green leaves. The latter also has a more branched inflorescence. Aloe catengiana also resembles the krantz-aloe (Aloe arborescens ) which is an ascending, much larger species with leaves which are not spotted.
Aloe catengiana is pollinated by sunbirds. The plants proliferates from the base and when damaged by grassland fires will simply re-sprout. The grey green leaf skin (epidermis) is covered with a waxy layer, which protects the leaves against excessive sunlight and moisture loss.
Seeds are dispersed by wind during the winter months (July-August), just before the onset of the spring rains.In its native habitat the leaves turn purplish (anthocyanin pigment) and more or less the same colour as the sandstone rocks during the dry winter season, becoming bluish-green during the moist summer months.
Uses and cultural aspects
No uses have been recorded.
Growing Aloe catengiana
Aloe catengiana is an easily grown plant and can be propagated both vegetatively or by seed. Cuttings ranging from 100-150 mm in length root rapidly in moist sand during spring or summer. A rooting hormone is not required. The plants grow rapidly, shooting from the base. They can be planted out in containers or on rockeries and a generous application of compost should boost its performance. The best time for growing it from seed is spring or summer. It is recommended to add a fungicide when watering. The plants grow fairly fast and can reach flowering stage in about three years. They are best sown in a sandy, well-drained potting soil in a warm shady position in standard seed trays. Germination usually takes place within three weeks. Cover seed with a thin layer of sand (1-2 mm) and keep moist. The seedlings can be planted out in individual bags or containers as soon as they are large enough to handle. Keep in a cool situation and provide sufficient moisture.
Aloe catengiana thrives in containers (or large hanging baskets), on steep embankments or in rockeries. It should preferably be grown in full sun. The species proliferates readily and soon becomes spreading or pendent. It flowers readily. It is best grown in well drained sandy soil and an annual compost dressing will improve its growth performance. When grown in containers the plants should be kept dry in summer and protected from severe frosts. They are fairly pest-free, but will rapidly rot if kept too wet or in poorly drained soil. Aloe catengiana responds well to feeding with organic fertiliser, which should be applied during spring and summer.
References and suggested reading
- Gunn, M. & Codd, L.E.1981. Botanical exploration of southern Africa. Balkema, Cape Town.
- Reynolds, G.W. 1966. The Aloes of Tropical Africa and Madagascar. The Trustees @of the Aloe book fund, Swaziland.
- Rothmann, S. 2004. Aloes, aristocrats of @the Namibian Flora. ST Promotions, Swakopmund, Namibia (firstname.lastname@example.org).
- Van Jaarsveld, E. J. & Van Wyk, A.E. 2004. Aloe omavandae (Aloaceae), new species from the Kaokoveld, northwestern Nambia. Haseltonia 10: 41-43.
- Van Jaarsveld, E. J. & Van Wyk, A.E. 2005. Aloe omavandae. Flowering plants of Africa 59: 2-6. Plate 2201.
Ernst van Jaarsveld