SA Orchids: Habenaria

This is a very large pantropical genus with 35 species in southern Africa. The genus is almost entirely confined to the summer-rainfall area, where the plants grow singly or in small groups in forest, savanna, dune scrub, marsh or grassland. The species of this genus flower mainly in summer, later in the year than other terrestrial orchids. Two species (H. arenaria and H. laevigata) are known from the winter-rainfall region. Habenaria species have small to medium-sized flowers. They are frequently delicate and bizarre in structure and are mostly greenish, yellowish or whitish in color. They often emit a sweet scent in the evening to attract moths which act as pollinators.

Description

Habenaria species have small to large underground root tubers and erect stems 20 to 80 cm in length. Leaves are lanceolate (lance-shaped) or ovate (round), and are borne either along the stem (cauline) or only at the base (basal). If basal, the leaves lie flat on the ground. The flowers are mostly green, white, yellow and green or white and green; the few exceptions with brilliant red flowers are not found in South Africa. In our species the flowers are resupinate (i.e. the lip faces down) and usually small, but there are some medium-sized or large-flowered species. Petals are either unlobed or deeply two-lobed. Lips are usually three-lobed and have a long spur that is sometimes swollen at the end. The column is frequently rather complicated, with long organs sticking out of it (stigma processes, lateral rostellum arms, anther canals). The plant is deciduous, with the entire above-ground part of the plant dying back each year.

Cultivation

Plants of the genus Habenaria are rarely found in collections of living plants as they have very little appeal to growers due to their inconspicuous flowers which lack brilliant colours. The species which are cultivated, however, are usually those that have beautifully marked foliage.

Plants are best grown in deep pots (e.g. 20 cm depth, place tubers at 10 cm depth) in a well drained medium consisting of 50 % river sand, 40 % leaf mulch and 10 % vermiculite. Plants are best grown in a temperate environment with 50-70 % shading and excellent ventilation.

Regular watering should be given during the growth season, from spring to autumn. As soon as autumn cooling sets in reduce watering to once every two weeks. During cold winter months do not water. It is, however, vital to watch that the medium does not dehydrate completely. To prevent this drench the pot occasionally and allow to dry. Do not keep the medium damp. Only after new shoots emerge at the end of winter commence with watering once every two weeks for the spring season and once or twice a week as required for the summer season.

A slow release fertiliser such as Osmocote can be applied during spring. Pests to watch for are aphids.

Selected species
H. arenaria ('dune orchid'), H. epipactidea, H. laevigata, H. malacophylla, H. cornuta, H. clavata, H. dives, H. falcicornis, H. nyikana, H. schimperiana, H. dregeana, H.lithophila

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