Plants in the Lüderitz environs – Black Mountain and blood finger

Text and photos by Luise Hoffmann

Arriving at Lüderitz you may feel that you have reached a very remote and rocky place. Nevertheless, this little town and its surroundings harbour many surprises. Most fascinating of these is the great variety of plants found on the peninsula south of Lüderitz.

After a rare good rainy season you may find large areas covered in a low-growing succulent known as blood finger (Mesembryanthemum cryptanthum), so-named due to its stems and leaves that can be green but are usually very red. The cylindrical stems can have a diameter of up to 10 millimetres and the rather inconspicuous flowers are white to pale yellow. A great number of different mesembs – as they are referred to for easier pronunciation – occur in the southern Namib.

There are two explanations for the name. These are mesos, Greek for ‘in the middle’, embryon, Greek for ‘embryo’, and anthemon, Greek for ‘flowers’, which refers to the central attachment of the seeds in the ovary, while mesembria (Greek), means ‘midday’ and refers to the flowers opening at midday, hence the German common name Mittagsblüher for this genus. The species name cryptanthum refers to the relatively small ‘cryptic’ flowers of this plant. The large bladder cells often found on these plants are a water-storage adaptation to their dry habitat.

Mesemb & Drosanthemum

Other plants of a different colour show up very well against the red background; here it is Drosanthemum luederitzii, whose leaves are also typically covered in glistening bladder cells. The Greek word drosos meaning ‘dew’ refers to this feature, which is also found on the sepals, to which the Greek word anthos refers. This species is found as far north as Swakopmund.

In combination with several other plant species, blood finger splashes the forbidding desert landscape with colour. The stunning colour combination of this view is composed of a small greenish-turquoise lake tinted by salts dissolved in the water. The opposite slope is covered in blood finger.

The so-called Black Mountain began its existence millions of years ago, when basaltic lava erupted onto what was then the bottom of a primeval ocean. Tectonic turmoil first buried these lava intrusions at great depths where intense heat and pressure metamorphosed them into black amphibolite, which was then thrust upwards far above sea level and eventually exposed by the forces of erosion.

Tripteris and Augea

There is an incredible diversity of plants in this area. The plant with the swollen leaves is called Augea capensis, German Dicker-Finger-Busch; Afrikaans kindervingertjies and kinderpieletjies. It is a very succulent yellow-green annual often found along road verges in sandy soil. The fleshy, waxy-looking leaves widen towards the tip, ending in a minute sharp point. The 10-chambered fruit, fleshy at first, becomes brown and papery and splits open when dry. The genus, Augea, was named after Johann Andreas Auge, a German gardener and collector, and the species capensis, after the Cape of Good Hope.

Didelta carnosa has large yellow flowers and the broadly triangular flower bracts persist on the plant. It is known as green didelta, in Afrikaans as perdeblom, and occurs from Aus towards Lüderitz and down to the Orange River and eastwards towards the Karas Mountains and Warmbad.

Didelta carnosa

Many other plants are quite small and to really appreciate the multitude of different shapes you have to get out of your vehicle and bend down or crouch. You will be richly rewarded. Plants resembling miniature trees most likely belong to the genus Othonna, Greek for ‘linen’ or ‘sail’, probably referring to the bristles of the fruit that facilitate wind dispersal.

Like the central Namib, the Lüderitz peninsula also has its lichen fields. The extent and composition of the lichen communities in Namibia is unique and much research into these organisms still needs to be done. A lichen is a composite organism consisting of an alga and a fungus.

These two components have a symbiotic relationship, the fungus attaching the plant to the substrate while the alga absorbs moisture – mostly from the atmosphere – and food through photosynthesis. The fungus controls the shape of the lichen, which can be upright and resemble grey-green grass or it may encrust stones, rock faces and even other plants in bright yellow, orange or black.

Various lichen

Lichens are the first organisms to colonise bare habitats, forming a crust that protects the soil from wind and even water erosion and so prepares it for other more developed plant species. They can survive long periods of drought but are very vulnerable to being trodden on or driven over.

Even being pressed into the substrate by just a centimetre or two by the weight of a passing vehicle alters the angle at which they face the sun and the prevailing moisture-laden wind and this may set them back by decades. This is one of the reasons why drivers should always stick to existing roads and even tread softly when walking among lichens.

The growth of lichens is usually favoured by high humidity, cool temperatures and low-light intensity, all of which are provided by the frequent occurrence of fog along Namibia’s coast. They are well adapted to absorbing available moisture very rapidly, but also dry out rapidly. They grow extremely slowly and their lifespan can be measured in tens and even hundreds of years.

Zygophyllum and synamtophyllum

Because they are unable to withstand air pollution, one of their uses is as an indicator of pollution. Certain European lichens have been used in the manufacturing of perfume, antibiotics and colouring agents, while in Namibia springbok have been seen grazing on them.  The Damara tern sometimes lays its single egg in a scrape among the lichens.

Read more about the fascinating flora and the geology of the vicinity of Lüderitz in Wildflowers of the Southern Namib by Coleen Mannheimer, Gillian Maggs-Kölling, Herta Kolberg and Silke Rügheimer, and in Namibia’s Fascinating Geology by Nicole Grünert.

Article originally published in the Flamingo May 2009 publication