Disa

Disa is a genus of mainly ground orchids, as well as a few species growing on rock surfaces or on other plants (but not as parasites). Annual above-ground stems, some with additional sterile shoots, grow from globose or ellipsoid below-ground tubers.

The leaves growing from the ground, at the plant base or up the stem are linear, lanceolate or ovate. Most plants have green leaves at bloomtime, flat or folded in. A few species are hysteranthous, bearing leaves when there are no flowers.

The inflorescence is a lax or dense spike or corymb, cylindrical or flat-topped, rarely one-flowering. Some species have resupinate flowers, a few doubly resupinate. Resupinate means that the flower turns upside down, the lip that developed in bud at the top presented below in the open flower. Flower colours range widely from white, red, pink, yellow and brown to green, blue or purple.

The floral bracts are usually lanceolate and acutely pointe, in some species dry and membranous. The sepals are free, often ending in abrupt, small, pointed tips. The median sepal is often helmet-shaped and bearing a sac-like or elongated spur. The lateral sepals are flat or boat-shaped, spreading or recurved.

The lateral petals are usually smaller than the sepals, ovate to oblong or sickle-shaped and fused at the base with the gynostemium, the central column comprising both male and female floral parts. The petal tips usually have lobes or pairs of them facing the inside of the flower. The lip may be linear, strap-shaped, narrowly lance-shaped, spoon-shaped or egg-shaped. It is sometimes pendent, notched, scalloped or fringed.

The tip of the column or gynostemium has an erect, horizontally reflexed or pendent anther with parallel lobes. There are two pollinia containing the pollen grains, connected to one or two sticky pads, the viscidia. The pad-like stigma may be stalked. The rostellum, the projecting part that separates the male and female parts, may be three-lobed. The inferior ovary is twisted in some species.

There are about 162 Disa species in Africa, Arabia and on some of the nearby islands, the plants botanically divided recently into 18 sections. About 131 of the species occur widely across southern Africa. Some species are rare and localised, others widespread and fairly common.

The genus is named after Disa, a mythical woman of the far north. Her exceptional qualities made the ancient Swedish king of the time summon her in ridiculous demand to appear before him, neither clothed nor naked, neither walking nor riding. She appeared in a fishing-net, one foot on a buck, the other on a sledge drawn by two men. Needless to say, she became queen and the Disa genus could be appropriately named in 1767 by Swedish botanist, Peter Bergius.

Disa uniflora, the spectacular red disa or The Pride of Table Mountain stands out as an ornamental. The plant in picture is Disa baurii (Liltved and Johnson, 2012; Leistner, (Ed.), 2000; Wikipedia).