Category: succulents

The survival of the fattest: Where do succulents grow?

Succulents are mainly found in areas where dry periods are regularly followed by a rainy season, so that the plants can fill their storage organs for the next dry season. This means they are relatively rare in regions where precipitation is very unpredictable or the dry periods are often longer than a year.
In other words, although we tend to think of succulents as typical desert-dwellers, in fact they rarely occur in extremely arid areas. (An area is usually called arid when it receives 70–150 mm precipitation per year and semi-arid when the figures are 150–400 mm per year).
In some coastal deserts with extremely low rainfall, such as the Atacama in South America and the Namib in southern Africa, succulents can survive and even thrive because of the runoff from nightly fog. To give you some idea of the importance of this phenomenon: for Swakopmund in Namibia, fog is recorded on 150 days per year.
The presence of succulents is limited by low temperatures, especially when these occur in the growing period. Several species though can stand temperatures as low as -10°C for a short while.
Factors such as soil type, drainage, wind speed, aspect, relief etc. play a role too. As a result of all this, succulent plants are not only found in more or less extended dry zones, but also in smaller pockets of dryness in environments that are generally much wetter (think of places like dunes, inselbergs, rocky outcrops etc.)

There are 2 main distribution centres for succulents:
Firstly we have the dry areas of the new world: Arizona, Mexico, central and South America. Here we mainly find cacti, but there also many other succulents.
The second centre is formed by the dry regions of Africa, including the Canary islands, Madagascar and Socotra, as well as the southern part of the Arabian peninsula. Far richer than any other region here is the Succulent Karoo, the winter-rainfall area of southern Africa, which includes one of the mist deserts mentioned above.
Europe, Asia and Australia are home to relatively very few succulents.

In conjunction with this post a new photo gallery is published with pictures of
— habitats where succulents are known to occur and of
— succulents showing  much more of their natural environment than usually in my pictures.
Go to gallery.


For other posts in this series click here.

The survival of the fattest: What are succulents, actually?

The one thing that sets succulents apart from all other plants is the ability to store water to allow the plants to remain active even in periods when no water is available.
Although this does not make them immune to extreme lack of water, it of course helps to alleviate problems caused by temporary droughts.
Succulence is often described as a structural phenomenon, something you can see and feel, so that plants are called ‘‘succulent’’ when the leaves, stems and/or roots have a swollen appearance.
We can also look at succulence  from a functional perspective, wondering how it affects the way a plant functions and survives in its habitat.
As these posts are not intended for professional botanists but for amateur plant aficionados, they are mainly concerned with the visible adaptations succulents have developed.
When looking at a collection of succulent plants it is easy to see that “some of them are more succulent than others”.
It is sometimes less easy, or even nearly impossible, to say whether a certain plant should be called a succulent or not. In other words, succulence is a continuum and there is no clear cut-off point between succulent and non-succulent plants.

Not all
succulents are
created equal

So when we talk about ‘‘succulents’’, we should bear in mind that this is in fact shorthand for more correct but also slightly complicated phrases, such as ‘‘plants with notable succulence’’ or ‘‘very succulent plants’’.
There are many different kinds of succulent features, which may be combined in several ways and water may be stored in more than one organ. For these reasons it is very difficult to give a comprehensive (as well as comprehensible) definition of what succulents are.

The following definition is easy  to understand:
      “A succulent is a plant that stores water in its tissues as a mechanism to survive periods of drought in the growing phase.”
List of southern African succulent plants, G. F. Smith e.a., 1997.

The two definitions below are more comprehensive:
     “A succulent is a plant possessing at least one succulent tissue. A succulent tissue is a living tissue that, besides possible other tasks, serves and guarantees an at least temporary storage of utilizable water, which makes the plant temporarily independent from external water supply, when soil water conditions have deteriorated such that the root is no longer able to provide the necessary water from the soil”
Life Stategies of succulents in deserts, D. J. Von Willert e.a., 1992.

     “Succulence can be defined as follows: = storage of utilizable water in living tissues in one or several plant parts in such a way to allow the plant to be temporarily independent from external water supply but to retain at least some physiological activity.”
Living under temporarily arid conditions ­ succulence as an adaptive strategy, Eggli U. and R.Nyffeler, Bradleya 27/2009, pages 13-36.

Succulence is a tried and tested solution for plants living in dry environments, but it is not the only possible strategy for surviving there. In the wild, succulents are often growing together with plants that use very different adaptations to stay alive.
The ability to store water has developed independently in around 50 different plant families. For many plants it is apparently important to have some degree of succulence, as it occurs in 4-5 % of higher plants. Estimates vary from about 8000 to plus or minus 13.000 -out of approximately 260.000 species (depending on what you call a succulent and how you define a species).

As it is of little use to store something that you cannot keep safe, succulents have also developed a variety of means to conserve the stored water.
It is this combination of storing and conserving water that causes the peculiar appearances of these plants.

When you follow this link, you will be taken to a gallery giving you some idea of the enormous diversity in size, shape and structure of (mainly South African) succulents.

For other posts in this series click here.

The survival of the fattest: Introduction

A photograph of Lithops olivacea in the wild, for comparison with the drawing below of the same species in cultivation.

The drawings above, were in the first book on succulents I ever saw. They showed plants apparently called “living stones” and made such an impression on me that over sixty years later, I still know exactly how and where I came across them. Because they looked so peculiar, at first I thought they were figments of the artist’s imagination, but I soon found out that plants like these really existed and this was the start of a lifelong fascination.
From the beginning, one of the most intriguing aspects of succulents to me has been the way in which they manage to survive in the most difficult situations. Over time I visited many countries to look for succulents in their natural habitats and this only added to that feeling of wonder.
In 2001, my wife and I moved to South Africa, which gave me more time and opportunity to see and photograph succulents on their home turf.
Some years later, I was asked by one of the local garden clubs to give a talk on succulent plants. Over the years, I had often done this in the Netherlands and neighbouring countries, but this was the first time I was asked to do so in South Africa. I quickly realised that the invitation was both a challenge and an opportunity to give a completely different talk from the ones I was used to give. When I thought about why exactly I was so intrigued by these plants, I was automatically taken back to my first encounter with them. At first it was their peculiar and often even bizarre appearance that was so appealing. As I came to know more about them, I found out that this was in fact the result of a long process in which they developed adaptations to the conditions they have to cope with in their homelands.
I decided to make this the subject of my talk and called it “The survival of the fattest” (with apologies to Charles Darwin).
As the series of posts of which this is the first instalment, is based on and inspired by that talk, it seemed fitting to give it the same title.
Because succulents show such a bewildering variety in adaptations, it is not easy to recognise and understand the common elements. I have tried to arrange the material in this series of posts in such a way that at least some order is created out of chaos.
There is always more than one way to tell a story and the author has to choose which way to take. Each choice excludes a number of other possible ones. I can only hope that the choices I have made here do justice to the subject as well as appeal to the reader.
The main purpose of the pictures in these posts is to show what beauty can result from adversity; the text is meant to explain the mechanisms behind it all in understandable language. As I have lived in South Africa for a long time now and most of my pictures have been made there, it seemed logical and practical to approach the subject mainly from a South African perspective. This also makes sense because the dry parts of Southern Africa are among the richest succulent areas in the world; about half of all succulents occur here.

Other posts in this series:

What are succulents, actually?

Where  do succulents grow?

Problems and solutions, part 1

Problems and solutions, part 2

Collecting water

Storing water

Succulent diversity A-Z

At this moment,  I’m working on a series of posts about succulents and how they survive in nature. The plan is to publish them interspersed with the usual posts and as the regular visitors have come to expect, the visual aspect will play a very important role.
As a kick off, I have created a new  picture gallery  with 70+ pictures showing the enormous range in size, shape and general morphology of (mainly South African) succulents.
If you would feel like making a comment, either positive or negative, please do!

Kalanchoe synsepala

This characteristic species always reminds me of strawberry plants, as it is the only Kalanchoe producing runners (sometimes up to over a meter long!). It is not uncommon in open, rocky places in the mountains of Madagascar’s Central Plateau.

The plants usually have a short thick stem and the leaves are variable in size, shape and colour, usually 6-15 cm long and 4-7 cm wide, glabrous or with short hairs; the margins may have strong teeth and are sometimes dissected.
The compact inflorescences have up to 30 white to purple flowers with a 7-12 mm long, 4-angled tube.

Cynanchum perrieri

One can come across this species on the gneiss and granite plateaux of Madagascar’s Central region at altitudes between 1200 and 1600 m, where it grows in full sun with Pachypodium densiflorum, Aloe capitata var. capitata, Euphorbia leucodendron ssp. leucodendron and other succulent and non- succulent plants.

It has  stems 0.8-1.5 m tall and 9-13 mm across, usually erect, not twining, round or slightly angled, covered with wax and smooth or slightly rough.
The inflorescences have 10-15 greenish-yellow, cup-shaped flowers.
Pictures taken near Zazafotsy, 12th  June 2017.

Haworthia mucronata var. mucronata

H. mucronata is a very variable species, often even at varietal level. One of the few constant characters is the fact that the leaves are soft , incurved and slightly pellucid, with translucent margins and keel.
Var. mucronata occurs from the Barrydale area  to north of Oudtshoorn.
All pictures were taken at the same spot within Barrydale itself: the first five on 8 Aug. 2017  (late winter/early spring), the last two on 28 Jan. 2016 (midsummer).


 

Aloe acutissima var. acutissima

Densely branched bushes of this variety, up to a meter tall and to more than a meter in diameter, occur from Fianarantsoa in the central highlands of Madagascar to Tulear in the southwest and Beloha in the south; in the highlands they are locally abundant.
They grow in thin soil on granite, gneiss and limestone rocks, often in the shade of other bushes.
The plants are variable in the size of the stems and leaves as well as the flowers.
On average the leaves are 30 x 4 cm, grey-green with reddish tinge, without markings.
The inflorescence is to 50 cm long, undivided or with 2-4 branches; the flowers are coral-red with pale red tips.

Antimima solida

The first name that comes to mind on seeing a plant of this species is probably Argyroderma fissum (unless you are a real expert of course).
The two species share the same growth form as well as size and shape of the leaves; often they also grow near to each other. Fortunately the fruits are rather different and stay on the plants for a long time. (The Antimima has fruits with 5 locules, whereas in Argyroderma fruits there are at least 10 compartments).
The finger-shaped leaves are up to 3 cm long. The flowers come mostly in threes and appear in May-July; they are pinkish-purple and 1.8-2.5 cm in diameter.

In some places the species forms large mats on flats or gentle loamy slopes with an open cover of quartz pebbles. According to the literature, it occurs in the Vredendal-Vanrhynsdorp area, but last year I also found plants in the northern half of the Knersvlakte.


Huernia guttata subsp. guttata

In this subspecies the stems have 4 or 5 angles; they are 2 to 10 cm long and 1-1.5 cm thick, grey-green, sometimes with faint purple-red spots.
The striking flowers are 2-7.5 cm in diameter and appear in November-April.
Plants are found from Somerset East to near Willowmore, between Uniondale and Joubertina and also between Oudtshoorn and Calitzdorp, under bushes on stony slopes.
The pictures shown here were all taken in the latter area and represent the former subsp. calitzdorpensis  (the plant in the third picture was growing next to the road, hence the specks of dust).