Gasteria tukhelensis Van Jaarsv.
Common names: Tugela ox-tongue (Eng.), Tugela-beestong (Afr.)
Gasteria tukhelensis is one of the more or less 20 species so far known of the popular, aloe-like genus Gasteria which is endemic to southern Africa.
Gasteria tukhelensis is a more or less stemless succulent, up to 250 mm high. It proliferates from the base and forms clusters up to 700 mm in diameter with 3-8 heads. The roots are succulent and up to 5 mm in diameter. The leaves are brittle and are produced in rosettes. They are 120-250 mm long and 30-50 mm broad at the base, triangular-lanceolate, sickle shaped (falcate) and curve upwards and sometimes backwards. Both surfaces are smooth and shiny, and dark green with faint white spots arranged in obscure transverse bands. The upper surface becomes channelled during the dry season and the lower surface keeled. The leaf margins are minutely toothed to almost smooth, and the tips are rounded or end in a sharp point. The juvenile leaves are arranged in opposite rows (distichous) and they are erectly spreading to patent. They are strap-shaped and their surface is covered with small tubercles.
The inflorescence is a spreading raceme up to 560 mm long, often with two side branches. Up to 11 flowers may be open at the same time. The flower stalks are drooping and 12-17 mm long. The perianth is tubular, 40-43 mm long and about 6 mm wide and pink; the upper half is white with green striations. The stamens protrude shortly from the perianth. Flowering time: Midsummer (December to March in the southern hemisphere).
After fertilization the capsule, which is 23-32 mm long, becomes erect. When it dehisces the black, 5-7 mm long and 2-3 mm broad seeds are released.
The species is not threatened due to its safe cliff face habitat. Although plants are only known from the type locality the species is presumed to be widespread in the valley.
Distribution and habitat
Gasteria species occur more or less in a continuous belt along the coastal parts of KwaZulu-Natal, always confined to dry river valleys. G. batesiana is found in the northern parts of the province and G. croucheri further south. Until 2003 there appeared to be a gap in the distribution of the genus in the dry Tugela River region. With the discovery of Gasteria tukhelensis this gap was filled. This species appears to be confined to the lower Tugela Valley near Kranskop and seems to be restricted to sheer cliff faces (altitude 440 m). It is found in crevices and on humus-rich ledges on shale rocks in dry savanna.
The rosettes grow in the shade in succulent thicket consisting of Euphorbia evansii, E. tirucalli, Portulacaria afra, Aloe rupestris, Aloe arborescens, Ficus ingens, Commiphora harveyi, Bulbine natalensis, Cotyledon orbiculata, Crassula nudicaulis, Crassula orbicularis, Crasula perfoliata var. perfoliata, Delosperma tradescantioides, Gerrardanthus macrorrhizus, Plectranthus hadiensis var. tomentosus and Petopentia natalensis. Although the vegetation of the KwaZulu-Natal region is well known, we know very little about the flora of the sheer cliff faces in the Tugela region, and it is likely to yield more new species.
The Tugela Valley has a dry subtropical climate and is situated in a rain shadow. Rainfall occurs mainly during the summer months and ranges from 500-700 mm per annum. Summers are very hot with temperatures frequently above 30º C. Winters are mild and frost is absent or very light.
Derivation of name and historical aspects
The specific epithet "tukhelensis" is derived from the Zulu name of the Tugela River.
Prior to 2003 no Gasteria species were known from the Tugela River region. As the habitat seemed to be ideal for plants of this genus the author arranged a rubber duck expedition on this river in 2003. He was accompanied by colleagues Phakamani Xaba, Adam Harrower and Werner Voigt as well as the historian Albert van Jaarsveld and Dr Ronny van Rooyen. Gasteria plants were spotted at Ngubevu growing on south-facing cliffs just east of the confluence of the Buffalo and Tugela Rivers. Upon investigation they were found to represent a new species endemic to the Tugela River region. The author published it together with Braam van Wyk in 2005.
Relationships Gasteria tukhelensis is related to G. batesiana, a smaller species with triangular, distinctly tuberculate leaves occurring further north in northern KZN, Swaziland and as far north as Penge in Mpumalanga. Gasteria tukhelensis is at once distinguished from G. batesiana by its large clusters, up to 600 mm in diameter, shiny leaves and slightly larger flowers (40-43 mm long) on longer pedicels (10-17 mm). The flowers of G. batesiana are 35-40 mm long and its pedicels 6-12 mm long.
The tubular flowers of Gasteria tukhelensis are rich in nectar and are pollinated by sunbirds during its flowering season in the summer months. After pollination the capsules which are borne on the elongated inflorescence become erect, as is typical of the Aloaceae family. The black flattened seeds are dispersed by the wind. The erect woody capsules (opening loculicidally) ensure that the seeds do not all fall out at once but that they are only released during strong gusts of wind which maximises the dispersal distance. Prolific seed production ensures a rich seed bank. The leaves are brittle and when grazed or disturbed, portions become detached, and when lying on the ground or in crevices will root and colonise new areas.
Growing Gasteria tukhelensis
As with most Gasteria species, cross pollination is essential for the production of viable seed. The species is easily propagated from leaf cuttings or seed. Seed can be sown during spring or summer. Sow in a sandy well drained potting soil in a warm shady position in standard seed trays. Germination takes place within 3 weeks. The seedlings grow slowly. Cover with a thin layer of sand (1-2 mm) and keep moist. The seedlings can be planted out in individual bags as soon as they are large enough to handle. Leaves can also be placed in potting soil. After removing leaves from the adult plant, let them lie for about 1 month so that a healing tissue can develop. Lay them on the soil in a horizontal position with the base lightly covered with soil. They should root within a month or two and small plants will proliferate from their bases. These can be planted out as soon as they are large and firm enough to handle.
Gasteria tukhelensis can be used as a pot plant on window sills, stoeps or outside on a rockery provided that frost is not severe. It grows best in partial or dappled shade such as the shady side of rocks or below shrubs. It may be given an annual compost dressing placed on top of the soil. Any organic fertiliser can be used if compost is not available. It is tolerant of a wide range of soil types and also grows well in the winter rainfall of the Western Cape where it should be occasionally moistened during the dry summer months.
- Van Jaarsveld, E.J. & Van Wyk A.E. 2005. Gasteria tukhelensis, a new species from KwaZulu-Natal. Bothalia 35, 2 (2005).
- Van Jaarsveld, E. J. 1994. Gasterias of southern Africa. A new revision of a major succulent group. Fernwood Press in association with the National Botanical Institute. Vlaeberg, Cape Town.
Ernst van Jaarsveld
Kirstenbosch National Botanical Garden
Plant Type: Succulent
SA Distribution: KwaZulu-Natal
Soil type: Sandy, Loam
Flowering season: Early Summer
PH: Acid, Neutral
Flower colour: Pink
Gardening skill: Easy