Gasteria excelsa Baker
Common names: thicket ox-tongue, regal ox-tongue (Eng.); ruigte-beestong (Afr.)
Gasteria excelsa is a medium-sized aloe-like plant bearing triangular, spreading, ascending, dark-mottled green leaves and a dense panicle of pinkish flowers during summer. It is often found on cliffs, both in Albany Thicket as well as Eastern Valley Bushveld in the Eastern Cape Province. It thrives in cultivation, easily grown from leaf cuttings or seed. It is one of the largest of the Gasteria species.
Plants with very short stem, robust, usually with solitary growth, rarely dividing to form small groups, and up to 600 mm tall and 750 mm in diameter. Roots fleshy, up to 3 mm in diameter. Leaves in a dense rosette, 100-400 mm long, 100-180 mm broad at the base, triangular to triangular-oblong, ascending, spreading to somewhat recurved, brittle; new plants proliferate from leaf fragments. The upper surface is channelled and dark green. The lower surface is somewhat convex with a distinct off-centre keel. Both surfaces are dark green with indistinct white spots arranged in transverse bands which (rarely) may be barely visible; rarely striated. The leaf surface is smooth, the margin often very sharp, white, semi-translucent, leathery, sometimes with a fine saw edge. The leaf end is acute or blunt, bearing a short hard point (mucro). Juvenile plants with leaves distichous (in two vertical rows on opposite sides of the stem), densely white-spotted, spreading, oblong, the upper surface with tubercles; the lower surface smooth, the leaf end blunt with a short hard point (mucro).
Inflorescence a very large spreading panicle, 1-3 per plant, 1.0--1.90 m tall by 1.5--2.4 m in diameter. The inflorescence stalk (scape) up to 34 mm in diameter at the base, branched 550-750 mm from the base, the side branches erectly spreading, rarely horizontally spreading, bearing 30-100 flowers, (500-2700 per plant); bracts 15-20 (-25) mm long and 15-25 (-30) mm broad at the base. Floral bracts 7-8 mm long and 2 mm broad at the base. Flower stalks (pedicels) 7-8 mm long. The flowers (perianth) 22-26 mm long, swollen basally for more than half of the perianth length, light pink to rarely white, 6-7 mm in diameter at the widest point. Stamens 20-22 mm long. Anthers oblong, 2 mm long. Ovary 7 mm long; 2.5 mm in diameter. Style 10-14 mm long, exceeding the anthers after flowering. Capsule 17-20 x 8-12 mm. Seeds 4-5 mm long and 2-3 mm wide.
Flowering period: Summer (November-February, Southern Hemisphere).
Gasteria excelsa is related to G. nitida which is a smaller grassland plant with much shorter leaves and bright orange-pink flowers.
The plants are common in their habitat, and not threatened. The sheer cliffs are difficult to negotiate and plants are thus well protected by their sheer habitat. Gasteria excelsa also has been well established in cultivation (ex situ preservation) and is grown by succulent plant enthusiasts all over the world.
Distribution and habitat
Gasteria excelsa is widely distributed in the Eastern Cape, from Port Alfred in the southwest to the Msikaba River in the northeast. It occurs from near sea level to as far inland as Somerset East in the south and Cala in the northeast to an altitude of 1400 m. The habitat varies from embankments to sheer rock faces, the vegetation is mainly Albany Thicket as well as Eastern Valley Bushveld. G. excelsa is generally confined to shady undergrowth or exposed south-facing cliffs, sometimes in open grassland. It grows on well drained sites on soil derived from shale and mudstone (Beaufort Group, Karoo Sequence), quartzitic sandstone and shale of the Witteberg Group, as well as dolerite.
Precipitation, ranging between 600 and 1000 mm per year, occurs mainly during summer. The climate is subtropical, and frost in its habitat is a rarity. The leaves are brittle and new plants will proliferate from broken leaf fragments. The habitat along the Kei River (near the N2 bridge) consists of Eastern Valley Bushveld (Mucina et al. 2006). The plants occur on well drained, shady south-facing cliffs.
The vegetation in the habitat includes Acacia karroo, Euphorbia triangularis, Cussonia spicata, Plumbago auriculata, Azima tetracantha, and Coddianthus rudis. Associated succulent species include Aloe ferox, Ornithogalum longibracteatum, Kalanchoe rotundifolia, Sansevieria hyacinthoides, Crassula perfoliata, Sarcostemma viminale and Haemanthus albiflos.
Derivation of name and historical aspects
Gasteria excelsa was named by the botanist John Gilbert Baker in 1880 from plants collected by Thomas Cooper at the Chalumna River (Eastern Cape). He introduced live plants into Europe.
Gasteria excelsa is pollinated by sunbirds. The succulent leaves enable the plant to cope with dry conditions. The mottled leaves blend in with the natural surroundings, and plants are thus well camouflaged and protected from herbivores. During stress the leaves becomes reddish. The reddish colour is due to a pigment, anthocyanin, which protects the plant during drought and puts a brake on photosynthesis.
Apart from their horticultural use, the plants are occasionally grown by local Xhosa people on roof tops in the Eastern Cape, as they believe them to be a protection from lightning.
Growing Gasteria excelsa
Gasteria excelsa thrives in cultivation both as a pot plant or on rockeries in thicket gardens. It also thrives in Mediterranean gardens where frost is not too severe. It is a slow grower, but when grown from cuttings it can flower within 3-4 years. Plants prefer partial shade, and in hot climates should therefore be protected from full sun.
A number of cultivars have been introduced into cultivation:
- Gasteria excelsa 'Gaika' grown at Kirstenbosch. This cultivar has striped leaves.
- Gasteria excelsa 'Nquancule' grown on a dry stone wall at Kirstenbosh National Botanical Garden.
'Gaika' - A form with striped leaves from near Stutterheim (Eastern Cape);
'Nquancule' - This plant has a very sharp leaf margin and thrives on dry stone walls;
'Cala' - A robust compact form from near Cala (Eastern Cape) with wrinkled leaf margins. Thrives in containers.
Easily propagated from seed or leaf cuttings. It is best to apply a fungicide when growing from seed. Sow during spring or summer in a warm, shady position in a sandy slightly acidic soil and keep moist. Cover with a thin layer of sand. Germination is usually within 3 weeks. Seedlings grow slowly and are best planted out about a year after sowing. Gasteria excelsa is easily grown from leaf cuttings. Allow the leaf cutting to form a heel by placing it on a dry window sill for at least a month. Cuttings are best rooted in clean sand. Once rooted, plants can be planted into individual containers. Plants react well to organic feeding (compost or any other liquid fertilizer). Gasteria excelsa can be watered throughout the year, however less so during summer.
- Mucina, L. & Rutherford, M.C. (eds) 2006. The vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19. South African National Biodiversity Institute, Pretoria.
- Van Jaarsveld, E.J. 1994. Gasterias of South Africa. Fernwood Press.
- Van Jaarsveld, E.J. 2007. The genus Gasteria, a synoptic review. Aloe 44: 4: 84-103.
Ernst van Jaarsveld
Kirstenbosch National Botanical Garden
Plant Type: Succulent
SA Distribution: Eastern Cape
Soil type: Sandy, Loam
Flowering season: Early Summer, Late Summer
PH: Acid, Neutral
Flower colour: Pink
Gardening skill: Average