Succulent plants come in all shapes and sizes. Some of them, like baobabs and certain cacti, are enormous and able to store great quantities of water. At the other end of the scale we find the results of a trend towards reduction that can be seen in several unrelated families such as Aizoaceae, Asphodelaceae, Ateraceae, Crassulaceae, Euphorbiaceae and Portulacaceae.
These miniature succulents are small and compact, not taller than a few centimetres, often little branched, without visible internodes and with more or less spherical leaves or stems.
Among succulent plant enthusiasts, miniatures are long –time favourites. This is hardly surprising, because even a small space can harbour a nice collection of them. There is also an amazing abundance of shapes and colours. Last but not least, there is a great variety in their survival needs.
There are many reasons for having a closer look at these dwarf-sized plants. Particularly interesting is the way they cope with the challenges of their environment and make use of opportunities. Not only are these plants interesting, but they are also very beautiful.
Being small has advantages and disadvantages. The most obvious advantage about being small is that you will need little water, food and space to thrive.
Because dwarf succulents can store only a small amounts of water at a time, their storage organs have to be filled at regular intervals, so the supply should be dependable. For that reason, the great majority of them occur in the Succulent Karoo, especially in Namaqualand with its predictable winter rainfall supplemented by even more reliable fog and dew.
The Succulent Karoo is not the only winter-rainfall desert in the world. Others are the southern Atacama Desert in Chile, the north-western part of Baja California and the southern coast of Morocco. The first two deserts support a lot of succulents, but few if any of these are miniatures. In that sense one could say that these little gems are a southern African ‘invention’.
Small succulents are often restricted to places where water easily runs off, like gravel plains and quartz fields. Between and under rocks and stones, rainwater is collected providing moisture for small plants. Dew and mist condenses on rocks and the moisture accumulated at their bases and in crevices.
Succulent organs filled with water are quite heavy. In miniature succulents most of the body weight is near the ground so that there is little or no need to build and maintain a strong support system. Because the plants are so compact they are far less exposed to external influences than other plants.
In the areas where succulents grow, wind is usually present ad is often hot and strong. The continuous replacement of air around the plants has a dehydrating effect, so that evaporation can be extreme. Apart from this the wind transports sand and dust, causing sand abrasion which may damage the plants and remove hairs or wax cover. Because of surface roughness, wind speed is zero at ground level, and wind becomes stronger with increasing height above the ground. It follows that the lower the plants, the less likely it will be to suffer from wind damage.
A drawback about being small is that smaller leaves and stems have a larger surface-area-to-volume ratio than larger ones. Due to this their transpiration is relatively higher and they are more prone to heat stress. The fact that dwarf succulents have more or less spherical leaves or stems helps to alleviate the problem.
Hiding underground also has its disadvantages. Because less surface area is available, photosynthesis is reduced, so growth is slowed down. Famous window plants that have found a way to reduce this problem are the vygies (Lithops, Frithia and Conophytum). Other examples are Haworthia and Bulbine.
The Succulent Karoo contains the richest concentration of succulents in the world. Whereas only about 140 species of stem succulents grow here, there are about 1700 species of leaf succulents, about 700 of which are small and compact.
Article adapted from Frans Noltee featured in VELD&FLORA, March 2013.