Three white Disa orchids are Verloren Valei specials, although infrequently seen.
By Gerrit van Ede
There are three Disas found on Verloren Valei that are basically white with some spots. While they are specials on the Reserve, they are not seen that often. Of these three, Disa aconitoides has the widest distribution—in fact, my first sighting of this Disa was at home near Pretoria. In contrast, Disa alticola has a very small footprint and, luckily for us, this includes Verloren Valei. The third, Disa Saxicola, has a disjointed footprint and is found in a small area in KwaZulu-Natal and a far larger area in Limpopo and Mpumalanga.
A closer look at these three species will show they each grow in very different biomes, and you will not usually find them growing together. To find all three being protected in one reserve is just fantastic.
It’s well worth keeping an eye out for these three lovely white orchids. If you are lucky enough to spot one, establishing the nature of the habitat will help you identify which particular one you have found.
Disa aconitoides
The species we call Disa aconitoides is in fact a subspecies, being Disa aconitoides subsp. aconitoides. But as this is the only subspecies that occurs in our region—South Africa and Swaziland—we are happy simply to call it Disa aconitoides. The name apparently means “looking like Aconitum”, a genus in the Ranunculus family. There are two other subspecies elsewhere in Africa.
This is the largest species of the three Verloren Valei specials, and the flower stem can stand up to 600mm high. The plant itself is not large, with five to 10 leaves spaced on the fertile shoot. The leaves are up to 80mm long and not more than 20mm broad. A sterile shoot is seldom produced. There can be up to 50 off-white to pale mauve flowers spaced (lax) on the inflorescence. Flowers often have darker mauve spots. Another characteristic is that flowers commonly face downwards at an angle of 45º.
This species occurs sporadically on grassland biomes, flowering between December and January at Verloren Valei. What makes it even more difficult to find is that the flower stem often does not stand upright, but bends downwards, making it hard to locate this species to show visitors.
Disa alticola
This little gem is to me reason enough for the existence of Verloren Valei! It is listed as Vulnerable on the Red Data list, and is endemic to the high-altitude areas in Mpumalanga. Its name, alticola or “dweller in high places”, reflects this characteristic—the plant is only found 2 000m above sea level, but my own impression is that they prefer an altitude of 2100m and higher.
Disa alticola is only found in a few of these high-lying areas, and Verloren Valei is fortunate to have several places where it is present. It occurs in small to medium-sized colonies, usually on quartzite sand over solid rock sheets, nearly waterlogged in the summer rainy season and dry in winter.
The plant, with a flowering stem, is about 150-170mm high. Three to four small linear leaves, each around 60mm long, carry a dense beetroot-red inflorescence with 10 to 35 white 10mm-broad flowers. Flowers may have a few red-mauve blotches on the helmet-shaped (or galea, in Botanical jargon) median dorsal sepal.
Flowering time is December and January but, depending on the weather, flowering is short-lived. Plants that are not flowering are easy to miss.
Disa saxicola
This beautiful little orchid prefers some shade and likes moisture. The name saxicola means “rock-dweller”, and it may be found in small colonies in suitable habitats, such as rock-strewn slopes near water streams, moss-covered ledges and moist spots not far from water. Their habitat is always well drained, moist and, in most cases, shady for at least part of the day. Disa saxicola can also grow on rocks, but obviously only when a suitable substrate in cracks or hollows is present, and the rocks are moist. In some areas, the plant is sometimes found growing on tree trunks.
It is never found in open grassland, waterlogged areas or even on the edges of a stream.
My first sighting of Disa saxicola at Verloren Valei was at the northern end of the Reserve where I spotted a north-facing area that was greener than the surrounding hillside. When I and my companion, Allen Abel, got closer to the spot, we could see that it was a moss-covered area under a slight overhang on a steep slope. As expected, we found Disa saxicola present and flowering.
The flower stem can be up to 400mm high. The plant has only a few leaves arranged on the stem (cauline leaves). The inflorescence may carry six to 25 flowers. Flowering time is December to January.
