The Phyto-Philes: Horse's Teeth
Created | Updated Mar 9, 2014
Horse's Teeth
Willem says: 'The Phyto-Philes are for plant lovers of every size and shape, colour and flavour. As with my Colours of Wildlife column, I'll be featuring one species per article, illustrated with sketches, paintings, and/or photos. Over time I hope to be showcasing the amazing diversity of weird and wonderful plants that occur in South Africa, while also from time to time looking at the flora of other countries. While featuring many spectacular species, I'll not be neglecting the smaller, more humble kinds that are nevertheless fascinating in their own right.'
What? An article about horse's teeth? Isn't this supposed to be a column featuring plants? Be not confused O Reader, this is indeed a plant, as you'll see when you inspect the pictures! It is a plant called 'horse's teeth' because of its resemblance to the ridged cheek teeth of a horse!
A Most Noteworthy Weirdosity
Among the many, many weird plants of South Africa, this is one of the standouts. Like some others you will probably need to closely inspect my pictures just to work out just what is going on here. My drawing shows a plant as it appears in nature most of the time: you will see these strange, flat, parallel ridges, somewhat greenish, only just protruding above the gravelly surface of the soil. These are only the tips of the leaves – compare them with the leaf tips of the Stone Plant. But while stone plants have rounded leaves, the horse's teeth has leaves with the tips flat with angular edges as if the tip of the leaf has been cleanly snipped off! Its scientific name is Haworthia truncata, being named for Adrian Hardy Haworth, an English botanist with an interest in South African succulents. The species name 'truncata' means 'truncate', that is to say with the tip cut off.
Cultivated plants of this species tend to look rather different. They grow mostly above the soil surface as you can see in the photos of the two specimens I include here. (They're not my own specimens, I took these photos of ones in the collection of another local succulent enthusiast). Also in the smaller specimen the leaf tips are a bit more rounded, but you can see the 'cut off leaf tips' clearly in the larger specimen. Also these ones show you how the leaves actually look: they occur in rosettes of neatly arranged parallel leaf rows. The tip of the leaf is semi-transparent. Just as in the stone plants, these transparent 'windows' in the leaf tips allow light to enter and hit the photosynthesizing chloroplasts deeper in the leaf body.
This species grows in the dry, semi-desert region of the Little Karroo in the south of South Africa. Because most of its body is buried below the soil, it can retain moisture and survive very long dry periods. Below the leaf rows it has short, fleshy roots with which it can rapidly absorb moisture from the infrequent rains. It is also very inconspicuous, especially during the dry summer when the leaf tips may even contract to below soil level! (This is done by the fleshy roots: when water evaporates from them, they shrink and shorten and pull the rosette down as they do!) It is therefore not often browsed by animals, but ostriches might peck them out. Unfortunately, ostrich farming is a big business in the Little Karroo and this might endanger the plants in many locations!
The Little Karroo receives its sparse rainfall mainly in winter, which is the active growth season for this species. It grows quite slowly, even in cultivation. It flowers in spring. Its inflorescence is thin and bears a few small whitish flowers. Haworthias are relatives of aloes, but have far less striking flowers. They are pollinated by long-tongued bees, mostly. The fruit are capsules which dry and split open to release the black, papery seeds.
The Haworthias
This species is just one of many others constituting the genus Haworthia. This genus only occurs in southern Africa, in nature, but is cultivated all over the world today. Haworthias are mostly very small succulents. They are bewilderingly diverse in their rosette shapes, colours and patterns. Apart from the horse's teeth, there are a few others that also grow with only the leaf tips exposed, but they look quite different. There is another form of the horse's teeth, the variant maughamii, which has rounder leaf tips not arranged in parallel rows. I hope to feature more Haworthias here soon, I have quite a collection of them!
Growing Horse's Teeth
This species unfortunately is rare in nature today, mostly as a result of people collecting them from the wild. There is no reason to do so any more, since the species has been in cultivation very long and growers can supply the market's needs much better than the natural population can. Seeds as well as plants can be ordered over the internet, and the plants can also be found in specialist succulent nurseries. They are especially avidly grown in Japan, where a few not-so-natural varieties have been developed as well. But I like them the way they look in the wild! To grow them from seed, sow the seed in a light soil of sand and loam with some gravel/pumice/perlite and also a bit of fine compost, covering them with a layer of at most 4mm (about a sixth of an inch). Keep moist but not wet, and warm … early summer is a good time. They should be kept in a sunny position. Germination should happen in a week or two. The seedlings can be planted out after their first season of growth. As with the Adromischus plants, horse's teeth can be grown from leaves, but this takes long and is not always reliable. Remove an entire leaf, preferably one of the lower ones, from the plant body in Autumn. Let it dry and form scar tissue for a week or two, and then plant it in a coarse, gravelly medium. Be patient; it will form roots over several months.
The main rosette will also produce offset-rosettes over time, and these can be detached and planted out to multiply the plants. It can also be grown from root cuttings. This has helped it a bit to survive collection from the wild: some rosettes have been dug out but leaving a root or two still in the ground, from which new rosettes have sprouted. This species can tolerate a few degrees below freezing in the wild, but likes a hot climate. It grows best in full sun or light shade.
