succulents Archives - Page 59 of 60

Machairophyllums flowering after fire

In an earlier post I referred to a fire that raged on the nearby Rooiberg about a year ago.
Approximately half a year after the fire we discovered a great number of flowering Machairophyllums in the burnt areas.
Although there are several populations on the Rooiberg, we had never found a flowering specimen before and we wondered why that was. Had we never been there in the right time of the year and of the day (the flowers open after dark) or did the plants, like so many others occurring in fynbos, need a fire to trigger flowering?
Last Sunday we decided to visit the mountain again and see if we could find out if the Machairophyllums in the not burned areas had flowered so profusely last year as well. This is easy to establish because the fruits stay on the plants for a long time. We saw a couple of hundred plants in perfect condition, but only very few with (max. 2-3) fruits. If you look at the accompanying pictures (taken last October), you will see how profusely the plants flower after a fire.
All in all It seems safe to say that this species of Machairophyllum -and probably the others too- may not be totally dependent on fire to trigger flowering, but that it certainly makes an enormous difference.
When I say “this species of Machairophyllum “ you probably wonder exactly what species we are talking about here. Comparing all the information from literature, I come to the conclusion it is most probably M. albidum. Apparently other people too have a problem deciding which is which in this genus: The Illustrated Handbook of Succulent Plants recognises 7 species but also says “The genus is under study and four or five species may only be distinguishable”.

#2012-10-23_DSC8026_lznres
This picture was taken at 6.32 PM, when there was still just enough light to use

Fifteen minutes later the light had gone. so I had to use flash for this and the next two pictures

Two interesting Euphorbias from the southern Great Karoo. Part 2: The start of a hybrid swarm?

Because this area harbours a variety of interesting succulents, we had high expectations of what we might come across. Nevertheless, the rest of the trip was rather boring. That is, till the moment George pointed out a big clump of what we both thought was Euphorbia stellispina, in a field next to the road. Finding that species in itself, would have been nice enough, but when we walked up to the plant, we discovered that it was much more special: about all the plant’s features were perfectly in between those of E. stellispina and E. heptagona. The result was spectacular.

Two pictures of the purported hybrid

When we searched the immediate surroundings, we found plants of both these species, which strengthened the idea that our plant was a hybrid between the two.

E. stellispina

E. heptagona

To make the find even more exciting, after some looking around we came across another hybrid between the same parents.

More interesting than beautiful

Here the results of the mix are totally different and far less appealing. On the other hand it is exciting to witness what may be the beginning of a hybrid swarm and it would be interesting to follow the population’s behaviour over some time.

Two interesting Euphorbias from the southern Great Karoo, part 1: E. braunsii

Last month my friend George Hatting and I decided to spend a Sunday looking for plants in the Prince Albert area. We had both been there before and discovered some interesting plants. After a nice drive over the spectacular Swartberg Pass, we arrived in Prince Albert and took a gravel road road from there heading east. Shortly after leaving town, we stopped at a place that looked promising and found a couple of beautiful small Euphorbia’s. They clearly were plants of E. braunsii, which is well known from the area.

This is how E. braunsii usually looks in the wild (well, normally without fruits, of course). Photo taken near Prince Albert on 10 Oct. 2012.

The peculiar thing was that they were in leaf, something I had never seen before and which is apparently a rare phenomenon. Digging into my literature I found no mention of the leaves, let alone a description or picture of them. The most likely explanation for this is that the leaves are short lived, as in the related (or maybe even identical) species E. rudis from Namaqualand and Namibia. Whatever is the case, I was quite chuffed to be there right on time to photograph the leaves, especially as they add an extra dimension to an already charming plant.

The four pictures above were taken on 24 Febr. 2013

Next time we will look at a natural hybrid we discovered on this same trip.

Miniature succulents, part 2

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 they are so compact, they are also far less exposed to external influences than other plants.

Plants like this Conophytum praesectum from near Pofadder are small enough to benefit from shade cast by pebbles

The fact that a great part of the plant is near to the soil has another -and rather unexpected- advantage. In the areas where succulents grow, wind is usually present and 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 (especially seedlings) 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 plant, the less likely it will be to suffer from wind damage.
A drawback of being small is that smaller leaves and stems have a larger surface-area-to-volume ratio than large ones. As a result, 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. With regard to minimising evaporation, a sphere is the ideal shape, as it combines the minimum surface area with the maximum internal volume. (The surface area of a flat leaf is about 40 times bigger than that of a perfect globe with the same contents).

In the rare Muiria hortenseae from the southern Little Karoo, the two leaves making up each body are fused almost completely, so that the flowers have to force their way out

In some cases, pairs of leaves have grown into one, so that each pair resembles a little globe. Densely packed leaves or stems can attain similar results.

In Crassula pyramidalis the leaves fit so densely together, that it first sight the plant looks like a stem succulent rather than a leaf succulent

Water loss from the surface of the plant can further be minimised by (the plant) hiding underground. In dry periods, the plants are often completely hidden in the soil, covered with the sand and dust blown over them. Only when the bodies fill out at the beginning of the rainy period do they appear above ground again.
Experiments have shown that in Lithops the rate of water loss is about a fifth lower in plants that are embedded in the soil than in those totally exposed.
In addition, the daily variation of temperature in the leaves is reduced. This is important during the hottest part of the day, when the parts of the plant that are furthest away from the soil surface, stay cooler than those nearer the ground.
Hiding underground also has its disadvantages. Because less surface area is available, photosynthesis is much reduced, so growth is slowed down.
The famous window plants have found a way to reduce this problem. These plants occur almost exclusively in the dry winter rainfall areas of southern Africa and are found in just a few families- most commonly the vygies (Aizoaceae, several genera). Other examples are Haworthia and Bulbine.

Haworthia truncata has a limited distribution area around Calitzdorp and Oudtshoorn. It is one of a number of Haworthias with windows

A perfect specimen of waterglasie (Bulbine mesembryanthoides)

The classic example is Fenestraria rhopalophylla: The plants are practically stem less and have club-shaped leaves with a translucent area on top.
As only a small part of the leaves is exposed to light, photosynthesis would normally be seriously hampered. The window at the top however, combined with translucent water-storage cells deeper inside the leaf, makes it possible for light to penetrate into the leaf and reach the inside of its mantle. Here, (there) are cells that contain chlorophyll and make photosynthesis possible.
The plants grow in the mist zone on the coast of northern South Africa and southern Namibia where the leaves are drawn into the ground by thick contractile roots. Usually the plants grow in deep sand, but sometimes they are found in pockets above dolomite rocks. Although the plants are only a few centimeters across, the root system may cover up to 2 metres. The mat of fine roots just underneath the surface is able to absorb the condensation of the moisture brought in by the sea fog, which is the main source of water for these plants.
The leaves are usually flush with the sand so that they do not suffer from the strong winds that blow almost daily.

This F. rhopalophylla ssp. aurantiaca was photographed south of Port Nolloth, in close proximity to the sea

The so-called stone plants – among the smallest flowering plants in the world- have followed a slightly different route. They have very thick leaves, often with dark green dots in their leaf tops. These dots contain no pigment and may be either large single cells or a group of smaller ones. They lie just below the epidermis and serve as micro windows, which may take up to over 40% of the leaf surface. In winter, when the sunlight is weak, the non-pigmented zones help it to penetrate into the leaves.

Lithops localis near Prince Albert, showing its many micro windows

A peculiar adaptation is shown by many members of the mesemb family (Aizoaceae), especially the dwarf ones, which are able to recycle water from old leaves to new ones.
This phenomenon was already discussed in an earlier post (Water recycling in succulents, 4th Dec. 2012), so please have a look there if you are interested.

In this article, I have tried to highlight some of the intriguing adaptations miniature succulents deploy in order to survive. Of course, these are only a few of the techniques and strategies they have in common with other succulents. But that is another story, for another day.

***

The original version of this article appeared in the most recent issue of Veld & Flora (March 2013). If you are interested in the immensely rich flora of South Africa, it is well worth visiting their website: www.botanicalsociety.org.za.

***

Since I wrote the article I acquired a new piece of software (Inspiration) which allows the user to make mind maps, concept maps, flow charts etc. in a very intuitive and easy way. I had tried out similar programs before, but never liked the results, nor the way they worked. To my mind, this program scores well on both points.

As I am currently working on a book on how succulents survive in the wild, I thought it might be helpful to use a diagram such as the one below, to make complicated processes and relations a bit clearer.
It would be great if readers would have a critical look at this diagram and tell me if it works for them. Many thanks in advance!

Miniature succulents; masters of survival. Part 1

A few months ago I mentioned an article that I had written for “Veld & Flora” . Now that this has been published, I will share it with you here in a slightly modified version.

***

Succulent plants come in all shapes and sizes. Some of them, like baobabs and certain cacti, are enormous, 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, Asteraceae, Crassulaceae, Euphorbiaceae and Portulacaceae. These miniature succulents are both small and compact, not taller than a few centimeters, often little branched, without visible internodes and with more or less spherical leaves or stem(s). (In case you don’t know: an internode is the part of a stem between the points where leaves or branches develop).

Sometimes the trend involves neoteny. This is a situation in which plants or animals retain juvenile or embryonic characteristics throughout their life span, but nevertheless are able to reproduce. (A famous case in the animal kingdom is the Mexican axolotl).

An interesting example in plants is the genus Oophytum, which only occurs on the Knersvlakte. It is a member of the Mitrophyllum group that only produces juvenile leaves. In effect, they are therefore perpetual seedlings.

Among succulent plant enthusiasts, miniatures are long-time favorites. This is hardly surprising, because even a small space can harbour a nice collection of them. There’s also an amazing abundance of shapes and colours, so that even without flowers there is always something to marvel over.
Last but not least, there’s great variety in their survival needs. In other words, both beginners and advanced growers will be able to find plants that fit their knowledge and ability. To grow some of these plants from seed to maturity is quite a feat, whereas others are much more amenable.
Even if you are not interested in keeping plants in captivity, there are many reasons for having a closer look at these dwarfs. In this article, we will focus on the way they cope with the challenges of their environment and make use of its opportunities.
Being small has both advantages and disadvantages, some of them evident, others much less so. Often the situation is rather complex. The solution for a problem may create a new problem, which in some cases is then (partly) remedied by another solution. Trying to understand this balancing act is an interesting exercise.
The accompanying pictures will hopefully convince you that these plants are not just interesting; they are also beautiful and visually stimulating.
The most obvious advantage of being small is that you need only little water, food and space to thrive. (Of course, the opposite is also true: when there is an abundance of these necessities, small succulents cannot compete with faster growing plants).
Because dwarf succulents can store only small amounts of water at a time, their storage organs have to be refilled 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 hygroscopic fruit of this Argyroderma delaetii is still open early in the morning, as a result of the heavy nightly dew

The Succulent Karoo is not the only winter-rainfall desert in the world. Others are the southern Atacama Desert in Chile, the northwestern part of Baja California and the southern coast of Morocco. The first two especially, 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”
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. During the growing season, which is not just moist but also cool, these miniatures profit from the warmth of the soil.

One of the few miniature succulents occurring outside the Succulent Karoo is this beautiful Frithia pulchra from Gauteng

Not many stem succulents qualify as a miniature, but this Euphorbia pseudoglobosa from the Little Karoo certainly does

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 often collected, providing moisture for small plants. In addition, dew and mist condenses on rocks and the moisture accumulates at their bases and in crevices. (Apart from water, this kind of habitat often also provides shade and protection from predators).

This Conophytum pellucidum, photographed near Kamieskroon, looks quite happy with the little bit of extra water that collects at the foot of a rock slab

To be continued.

An outstanding Huernia (Huernia praestans)

H. praestans was described by N. E. Brown in 1909 and judging from the name he gave it (praestans = outstanding; pre-eminent) he must have considered it to be something quite special. It is recorded from a relatively small area in the western part of the Little Karoo (from Montagu to around Ladismith and Vanwyksdorp).
Up to now I only know the species from one slope with a rather dense scrub vegetation between Hoeko and Ladismith, which is slightly east of the recorded distribution area.

H. praestans, east of Ladismith

When I first saw the plants, I thought they belonged to the much better known H. guttata, which occupies a wide area in the Eastern Cape and the eastern part of the Little Karoo. Its habitats from near Calitzdorp are only 40-50 kms away from the place mentioned above.
The main differences between the two species is the fact that H. guttata only has some bristles in the mouth of the tube, whereas in H. praestans they also occur on the lobes.
All in all little is known of H. praestans and it has been suggested that it is a hybrid between H. guttata and H. barbata. The latter has a very wide distribution area, from the Knersvlakte as far as Grahamstown in the Eastern Cape.

H. guttata, above (with Duvalia caespitosa) and H. barbata, Mom and Dad?

Warts and all

In a recent post (Cover up, 14th Jan.) I discussed how spines, hairs etc. help succulents conserve water. In some families we also come across plants where the leaves are (partly) covered in warts, papillae or tubercles. Although these are often highly decorative, it seemed likely to me that they would first and foremost serve a useful purpose. After doing a bit of research I came up with some interesting information.
It appears that the presence of these projections on stems or leaves has an advantage for the plants in that the breathing pores are hidden in the lower areas between them. This diminishes transpiration and protects the plants from dehydration.
In the case of warts, there is an additional advantage: their epidermis is rich in crystals and lies over cells that store up tannin. This combination makes the plant rather unattractive to herbivores.

Crassula tecta is named after the warts on the leaves (tecta =covered or protected)

Crassula corallina v. macrorrhiza (corallina = coral-like)

In Rhinephyllum graniforme the genus name means file leaf

Haworthia scabra is aptly named too (scabra = rough)

This Astroloba used to be called A. aspera (=rough). The current name A. corrugata has a similar meaning (wrinkled or furrowed)

Ruschia muricata is rough to the touch and that is exactly what muricata means

In the following two species the names make no reference to things like warts or tubercles, but it is clear that this is not because of lack of these.

Aloinopsis spathulata

Stomatium suaveolens

Under cover; ways and means of conserving water

When looking at all those beautiful and unusual forms, colours and textures in succulents, it is easy to think that all this is there for our enjoyment. I’m afraid that is not the case; most of it is purely functional. For me, instead of being disappointing, this fact adds to my pleasure and admiration. What can be more likeable than things that are both useful and pleasing to the eye? In this post we will have a look at some of the contraptions that succulents use to conserve water.
The one thing that sets succulents apart from all other plants is their ability to store water that they can use during periods when there is no external supply. Obviously it is not much use to store a lot of water if you do not have the means to conserve it as well. Managing the stored water sparingly, mainly has to do with reducing transpiration.
The rate at which plants lose water by transpiration is influenced by a number of factors: size and form of the plant, temperature, humidity, intensity of sunlight, precipitation, wind speed, land slope etc.
On some days the temperature of the soil surface may rise as high as 75 degrees C, but a few centimetres higher up it will usually be much cooler (up to 40 degrees less ). The two extremes will be separated by a layer of still air.
Comparable layers with gradients of humidity and temperature are found above plant surfaces; they have a great influence on transpiration. These layers are disturbed or even destroyed by wind. Because of this, many succulents have a cover of hairs, spines, etc. on the surfaces of their leaves or stems. This helps in producing and protecting these layers. Such a cover also gives a certain shade and helps to diminish exposure to strong radiation –especially when it is light in colour. It has been found that tissue temperatures below spines of the cholla cactus (Opuntia bigelovii) can be reduced by as much as 11 degrees C.

anacalbi2011_09_18#069_lznres(001)
In this Anacampseros albidiflora, short hairs on the leaves and long bristles between them, cooperate to keep the plant cool

Pelargonium barklyi is a tuberous plant. Although the leaves are short lived, it is apparently worthwhile to protect them with a cover of hairs

Haworthia arachnoidea gets its name from the spiderweb like cover of hairs. This variety is called scabrispina because the hairs are rough and hard like spines

In Senecio scaposus the leaves look like covered in felt

Many people think that spines are only there to protect the plants against browsing animals. In line with what we have discussed here, I think that spines play a certain role in that respect too, but that it is not the only, or even the most important, one.

In cases like Othonna euphorbioides (above) and Euphorbia stellispina -and in many other plants- the spines are actually hardened remains of inflorescences

Leaf and stem surfaces are often thickened too, or coated with a layer of wax (Senecio stapeliiformis, on top) or cork (Othonna herrei)

External water storage in succulents

The great majority of succulents stores water in stems, leaves and/or roots. Some of them however, mainly members of the vygie family (Aizoaceae) also make use of external storage. They have an epidermis covered with extremely enlarged and swollen cells (so called bladder cells) that are able to store water. Amazingly up to over 50 % of the total amount of water stored by the leaves can be located in these cells.

The cells have another advantage too: they are so big, that they create windless spaces above the stomata (breathing pores) so that transpiration is reduced. When a plant start suffering from drought stress, the cells collapse. This obstructs the passage of air to the stomata, so that water loss is reduced even further

One of the best known examples is the genus Drosanthemum (“dew flower”)

In this species (Mesembryanthemum guerichianum), the bladder cells are especially big on the calyx

Phyllobolus nitidus is named for its shining appearance (nitidus = glossy, polished or shining)

Exactly the same, but different; what post-production can do for your pictures.

A couple of months ago my wife and I were travelling to our farm near Matjiesfontein when we decided to have a short coffee break. As usual, I utilized this opportunity to quickly scan the area. Not far from the road I came across a plant of Cotyledon orbiculata (the beautiful form that used to be called undulata).

This picture shows my first attempt of photographing the plant.
It is not a bad photo, but neither does it convey the feeling I got when looking at the subject.

After cropping the picture this is what I got. Much better I thought, but too realistic.

Cropping in a slightly different way, combined with darkening the picture and enhancing the colours, resulted in this.
It seemed to me I was on the right track, but now the left side of the photo was too busy and distracting.

I had also made another picture, almost identical to the first one, but taken from a slightly different angle. When I closely compared the two, it became clear that the second one would be the best starting point for the picture I wanted.

I first treated the picture the same way as in number 3 and the lowered the contrast.
This is the end result, realistic enough to be of botanical value, but at the same time visually stimulating.