Aloe howmanii Reynolds
Common names: Howman’s cliff aloe (Eng.); waaier-grasaalwyn (Afr.)
A rare, cliff-dwelling aloe, only known from sheer, south-facing cliffs of the Chimanimani Mountains near Chimanimani (formerly Melsetter), in eastern Zimbabwe. It thrives in cultivation and flowers in autumn.
Aloe howmanii is a cliff-hanging shrublet, branching from the base and forming loose clusters of up to 10 heads, with branches up to 300 mm long. The lower stems are whitish grey, 12–14 mm in diameter. The leaves are succulent and sometimes almost rounded (subterete) and clasping (amplexicaul) at the base. They grow in 2 opposite rows (distichous), forming a fan. Each head usually has 4 functional leaves. The leaves of cultivated plants can be up to as much as 12, and 150–250 × 12–18 mm, becoming reddish and deciduous from below. The leaves are linear, slightly tapering, and slightly sickle-shaped; the upper surface is green, rounded (convex to slightly convex); the margins translucent (a 1.5 mm band) and with minute teeth (denticulate), the teeth are 2–4 mm apart; the lower surface is convex, the apex obtuse to subacute, cuspidate.
The inflorescence is simple 200–450 mm long, bending upwards, with the raceme erect, 40–120 mm long, sometimes almost in a head (subcapitate), bearing 12–45 flowers, the buds ascending, open flowers pendent. The bracts are ovate-acute, 3–6 × 2–4 mm, 3-nerved. The flower stalks are 10–15 mm long, orange. The flower (perianth) is orange-red, 24–25 × 7 mm, with a short stipe. The petals (tepals) are fused into a tube, 7 mm in diameter, green-tipped; the outer petals free to base, the inner slightly broader; filaments pale yellow, the 3 inner, narrow, lengthening before the outer; anthers exerted up to 2 mm; style pale yellow, with stigma exerted 1–2 mm; ovary pale-orange, 3 × 1.5 mm.
Flowering occurs mainly in autumn to early winter (April to June in the southern hemisphere).
Aloe howmanii is rare, but its inaccessible cliff face habitat, ensures its long-term survival.
Distribution and habitat
Aloe howmanii is known only from the Chimanimani Mountains, in southeastern Zimbabwe. It grows on sheer cliffs of sandstone rocks, at an altitude of 1 678–2 380 m. It is distributed from the Bundi Gorge, to the Musapa Gap. Plants grow pendent with the inflorescence upturned. The soil is poor in minerals and acidic. The vegetation consists of sub-alpine grassland and fynbos, with species of Erica, Leucospermum and Protea. Other species common in its habitat include, Plectranthus chimanimaniensis and P. hadiensis, many species of grass and sedge, as well as Xerophyta retinervis, and a species of Watsonia. Rainfall in the habitat is high and ranges from 1 000–2 000 mm per annum and is experienced mainly in summer, in the form of thunder showers. The summers are cool, very moist and humid, with frequent fog.
Derivation of name and historical aspects
Aloe howmanii was named after Roger Howman, the Native Commissioner at Ndanga and Zaka, who collected a plant on a sheer cliff during Easter 1940 (West 1974). It was named by Gilbert Reynolds in the Kirkia botanical Journal in 1961 (Reynolds 1966).
Aloe howmanii is pollinated by sunbirds. The plants proliferate from the base and when damaged by fires, will simply re-sprout. The south-facing cliffs provides ideal protection from large herbivores. The distinct, translucent, hyaline leaf margin ensures that sufficient light is allowed into the inner surface of the almost rounded (subterete) leaves, an adaptation to the shady cliffs. Plants escape fires because of their rocky habitat. Plants in habitat have only few leaves (2 pairs) along the apical portion of the stem. In cultivation the stems have up to 6 pairs of leaves.
Seeds are dispersed by wind in winter and spring (July–August), just before the onset of the summer rains.
No cultural or medicinal uses have been recorded.
Growing Aloe howmanii
Aloe howmanii is easily grown, planted in a cool climate and is best propagated by cuttings. Cuttings ranging from 100–150 mm long root rapidly in moist sand, in spring or summer. A rooting hormone is not required. The plants grow rapidly, shooting from the base. It is best planted in a mineral-poor, sandy, acidic soil, in light shade. Ample compost should boost its performance.
Aloe howmanii can be grown both, as a container plant, or in moist grassland gardens, where frost is not severe. It should preferably be grown in dry stone walls or on vertical walls where the plant can become pendent. The species proliferate from the base, forming small, hanging shrublets, with up to 10 stems. It is best grown in well-drained, sandy soil and an annual compost dressing will improve its growth performance. In warmer climates it should rather be grown in a cool greenhouse and kept dry during winter. When grown in containers, the plants should be protected from severe frost. They are fairly pest-free, but will rapidly rot if kept too wet or in poorly drained soil.
- Gunn, M. & Codd, L.E. 1980. Botanical exploration of southern Africa. Balkema, Cape town.
- Reynolds, G.W. 1966. The aloes of tropical Africa and Madagascar. Trustees of the Aloesof South Africa Book Fund, Mbabane.
- West, O.A 1974. A field guide to the aloes of Rhodesia. Bundu Series, Longman, Rhodesia.
E.J. van Jaarsveld
Kirstenbosch National Botanical Garden (Retired)
Extraordinary senior lecturer and researcher, Department of Biodiversity and Conservation, University of the W. Cape.
Plant Type: Shrub, Succulent
Soil type: Sandy
Flowering season: Autumn, Winter
Flower colour: Orange
Aspect: Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Average