These cacti are easily recognizable by the splendid crown blooms around the apical part of the stem, which can be small or medium in size. These are cacti suitable for expert growers as well as novice growers. Some species, in fact, require a fair amount of experience (among these, Mammillaria luethyi, Mammillaria pectinifera, Mammillaria solisoides, Mammillaria lasiacantha, Mammillaria senilis, Mammillaria herrerae); other species are suitable for anyone (among these, Mammillaria elongata, Mammillaria bombycina, Mammillaria prolifera, Mammillaria polythele, Mammillaria uncinata, Mammillaria bocasana, Mammillaria perbella, Mammillaria mystax). The stems can appear globose, often clustered, very harmonious and in some cases covered with thick hair or very white thorns. (…)

The origin of Mammillaria: where these cacti grow

As regards distribution, Mammillaria are native to the southwestern area of the United States and Mexico, where they grow in many states such as Tamaulipas, Hidalgo, Chiapas, Colima, Puebla, Oaxaca, Baja California, San Luis Potosí, Durango . Some species can also be found in the Caribbean area, in Central America and in some regions in the north of South America (such as Colombia and Venezuela). The range of origin of this genus is therefore very vast and this is also why the Mammillaria have been able to evolve in different ways, giving rise to a large number of species and subspecies.

The main characteristic of the entire genus, regardless of the shape of the specimen, is the presence of tubercles, small “cones” (similar to breasts, hence the name of the genus, from the latin term “mammilla”) which characterize the stem and which can be more or less marked depending on the species. The areoles and spines form at the apex of the tubercles. Some Mammillaria produce a latex that may resemble that contained in Euphorbia. By virtue of this, the distinction between Mammillaria Galactochylus (which contain latex) and Mammillaria Hydrochylus (which does not contain latex) was once in use.

The forms and species of Mammillaria

The thorns can take on many shapes and in some species they are hidden by thick white hair (Mammillaria hahniana). You can have short and pointed spines, long and twisted spines (Mammillaria camptotricha), hooked spines (Mammillaria uncinata, M. bombycina, M. perezdelarosae), as well as “combed” spines (Mammillaria pectinifera) and robust and long spines (Mammillaria compressa, Mammillaria magnimamma). Many species, in particular those traced back to the so-called lasiacantha group, have pure white thorns that completely cover the stem and which can turn gray with age. Among the white-spined species, Mammillaria perbella, M. candida, M. magallanii, M. lasiacantha, M. lenti, M. klissingiana, M. humboldtii, M. albiflora, M. herrerae, M. plumosa deserve mention.

How Mammillaria are grown

As regards cultivation, in general most of the species are also suitable for novice growers, since they are robust cacti and do not require any particular precautions compared to most cacti. Some species, however, can prove particularly challenging, to the point that their cultivation is recommended for those who have some experience with succulents. The particular sensitivity to water stagnation or the presence of taproot, which requires soils that are poor from an organic point of view and rich in aggregates and well-spaced watering.

Exposure and minimum temperatures

Regarding exposure, all Mammillaria want a lot of light for at least 6 hours a day, but only those whose stem is entirely covered with thorns (usually white ones) can stay in direct sun for many hours, as long as they are gradually accustomed to it starting from the end of March.

Mammillaria tolerate the cold well, as long as the soil is dry from the end of September.

Here you will find a PDF sheet entirely dedicated to the Mammillaria genus.

The English association The Mammillaria Society is dedicated to this type of cactus: anyone interested can take a look at their website at this link.

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Photos of some species of Mammillaria

Correlated articles

• How to grow cacti: the handbook
• The section dedicated to soils
• Most frequent questions and doubts
• All cultivation cards in pdf

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L'articolo Mammillaria, a genus of cactus that is essential in any self-respecting succulent collection proviene da Il fiore tra le spine.

In this article we deepen our knowledge of Echeveria laui, we understand why it has this appearance which is certainly not unique in the world of succulents but undoubtedly peculiar, and we learn how to grow it correctly. (…)

Premise

The Echeveria genus is part of the vast Crassulaceae family, leafy succulents with a variable shape from rosette to small tree. All Echeveria are native to the American continent and in particular to Mexico. Echeveria laui, in particular, is native to the Tomelin Caňon area, in the Mexican state of Oaxaca. The name of the genus was coined by the Swiss botanist Augustin Pyrame de Candolle (1778-1841), who in this way wanted to pay homage to the Mexican artist, botanist and naturalist Atanasio Echeverría y Godoy, to whom we owe a great deal of research (together to other botanists and researchers) on Mexican flora and fauna.

The stem of Echeveria is always rosette-shaped, initially flattened but over time tending to rise slightly in height following the development of the central stem from which the leaves branch out. And already in terms of leaves, the laui species differs from the majority of Echeveria: if generally the rosettes of these plants are made up of elongated leaves that end in a point, those of the laui species are blunt, rounded, almost ovoid, and give the together an even more harmonious and “soft” appearance.

Specifically, E. laui is a species (according to some authors it would actually be a hybrid) described for the first time in 1976. The plant immediately received great favor among nurserymen and collectors precisely because of its unique appearance in Crassulaceae family.

The wax coating

The real peculiarity of the laui species, however, is the massive production of wax coating (“farina” or cuticular wax) which entirely covers the leaves. The farina is nothing other than a wax produced by many succulents and some cacti (an example above all, the genus Copiapoa with the cinerea species), which serves to limit the transpiration of the liquids contained in the stems or leaves and to protect the plant from the sun’s ultraviolet rays. The wax is whitish and it is not it that gives the plant its blue color. As in many Echeveria, in fact, it is the leaves that are blue in colour, in the case of the laui more intense: the strong presence of wax accentuates this color and gives the plant a “waxy” appearance or similar to that would be obtained by painting the rosettes with blue paint (a very different thing from the horrible practice of actually painting the succulents with brightly colored paints to increase their sales!).

In some succulent plants – for example Copiapoa – the wax coating can be compact and resist watering. This is not the case with Echeveria laui: it is enough to touch a leaf with a finger to ruin the homogeneity of the colour. For this reason this plant must be watered from below, by immersion, or by wetting only the soil, avoiding watering from above, like rain. Any treatments with products such as Neem oil, copper oxychloride, etc., carried out by nebulization, should also be avoided. Finally, be careful when repotting, for obvious reasons. The task of flaring and repotting a plant by touching it as little as possible is undoubtedly difficult, but with some precautions it is possible to carry out the operation while limiting the aesthetic damage to a minimum. For example, you can grab the plant at the base, especially if you are dealing with specimens of a certain age, since in this way you can only touch the central stem. Or you can delicately hold the plant by the edges of the basal leaves and then grab the block of soil to place it in the new pot without touching the central part of the plant.

Cultivation

The cultivation of Echeveria is simple and within everyone’s reach and the laui species is no exception (except for what concerns watering and repotting, to be carried out with the precautions described above). Echeveria laui is a robust plant and resists prolonged drought as well as cold very well. Like all Echeveria, it fears water stagnation and should therefore be grown in substrates suitable for cacti or in substrates with 40% peat and 60% inert materials such as pumice, lapillus, gravel. Thanks to the strong presence of wax coating, E. laui resists direct sun well (if gradually accustomed from the end of March) but the ideal is to place it in a place where direct sun is limited to half a day. For the rest, lots of indirect light so that the plant can produce wax coating and maintain its compact appearance.

Watering must be moderate: water from mid-March to the end of October only when the soil is perfectly dry and fertilize with a specific product for succulent plants (with low nitrogen content) a couple of times a year.

During the winter, Echeveria should be sheltered from the rain but should not be brought indoors. In fact, these are plants capable of withstanding the cold very well, even up to 2 Celsius degrees above zero, with sporadic peaks at zero degrees. It is essential that the soil is dry from the end of October and that the plant has as much air as possible available. In the cold, the blue rosettes of E. laui can take on beautiful pink shades.

Where to place succulents in winter? Two very useful handbooks.

The growth times of this species are rather slow. The young plants grow relatively quickly in the first two or three years, then they slow down and it takes six to seven years to have rosettes of at least ten centimeters in diameter (the largest specimens can reach 15 centimeters in diameter).

Flowering

The flowering of E. laui is not dissimilar to those of other Echeveria species: the floral stem, up to 30 centimeters long in adult specimens, develops in late spring and between the end of spring and summer. It emerges from the center of the rosette (although in some cases there may be multiple stems, one from the center and others from the sides of the rosette), grows in height and then takes on an arched shape. The actual yellow and orange flowers form from the stem, protected by thick, fleshy bracts.

Propagation

The propagation of this wonderful succulent takes place in spring and can be done through sowing or, more simply, by leaf cutting, as for any other species of Echeveria. It is sufficient to remove a well-formed leaf, let it dry for at least a week in a shaded place so that the “callus” forms on the part detached from the mother plant, and then place the leaf on sand or even peat with a few inerts (pumice, perlite). For the first few weeks you will not have to water but it will be sufficient to mist often. Over the course of a few weeks, roots or new, tiny leaves will begin to emerge from the attachment of the leaf to the rosette. For the first few months we proceed with frequent nebulizations and when the new plant begins to be characterized and equipped with roots we can proceed with the first repotting.

Adversity

Robust plants, Echeveria fear two things more than anything else: water stagnation, which leads to root rot, and cochineal. A common enemy of all succulents, cochineal can be cottony or radical. The first forms white tufts that nestle among the leaves, near the central stem; the second is decidedly more insidious since it hides in the roots and its presence is only noticed when repotting or, unfortunately, when it is too late and the plant shows signs of suffering such as the wilting of the leaves, often followed by induced rot from the weakening of the plant caused by cochineal.

To find out more about succulent parasites, learn to recognize them and intervene when necessary, you can read this article. Other articles on parasites and diseases of succulent plants are collected in this section of the site.

At this link you will find a detailed downloadable PDF sheet (4 pages) dedicated to the Echeveria genus.

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Correlated articles

• Succulents
• Plant of the day
• Differences between cacti and succulents
• Inert and materials
• Repotting: all the articles

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L'articolo Splendid but… untouchable: Echeveria laui, when the sky is reflected in a succulent plant proviene da Il fiore tra le spine.

Those who have been cultivating cacti for some time know it well:  Melocactus  are as fascinating as they are “capricious” and you have to come to terms with it. In this article we deepen the knowledge with this genus, in particular from the point of view of the needs, so as to grow robust specimens and limit losses as much as possible. (…)

Introduction

It is usually said that Melocactus and Discocactus (similar genus in some ways) are plants that are loved and hated at the same time. Yes, because if in fact  Melocactus  have their own undoubted charm, at the same time they are among the most mangy cacti to cultivate. Or rather, all things considered, cultivation is not difficult, the fact is that these plants have a marked “tendency to suicide”: having reached a certain stage (almost always when they have formed the cephalium) they tend to lose their roots and only in rare cases they manage to reform the root system, unlike what happens with most cacti. In summary, it can be said that until Melocactus do not develop the cephalium, they have the same needs as other cacti and are not difficult to grow. Once the cephalium is formed – which is their characteristic element – they become extremely delicate plants,  they cannot bear repotting and do not tolerate low temperatures. All this in cultivation, since these plants abound in nature and manage to be quite long-lived.

Distribution and history

Fundamental, as for all plants, is the knowledge of the area of ​​origin of this genus, knowledge that can provide useful data for the cultivation of these plants. Well, all Melocactus are native to the warm areas of the American continent, in particular south-western Mexico, the Antilles, Cuba, Colombia, Venezuela, Peru, Ecuador and, above all, Brazil. It follows that these are cacti originating from the central belt of the continent, where temperatures are warmer than, for example, those of the American states or northern Mexico. It is precisely for this reason that Melocactus do not tolerate the cold, unlike most other cacti (except for epiphytes).

From a historical point of view, the Melocactus mark a starting point in the story of the study of cacti, since according to many sources, these plants were the first cacti encountered by Europeans during their expeditions to the Americas at the end of the fifteenth century. As far as it turns out, Christopher Columbus himself observed some specimens in the West Indies, precisely in conjunction with his landing on the American continent. It is clear that for Europeans, who did not know cacti in any way since these plants originate exclusively from the Americas, from a botanical point of view that meeting represented an enormous surprise. It is no coincidence that several specimens of these plants were sent to Europe to be subjected to in-depth studies (and it is to be assumed that only a very few specimens torn from their habitat arrived overseas alive and even those few, if equipped with a cephalium, lasted a few months).

If you want to learn more about the distribution of cacti and succulents in the world you can consult this article, complete with maps.

As further confirmation of what is reported by the sources, there would be the fact that the very name attributed to these plants would probably be the origin of the word “cactus”, deriving from the Greek “kaktos“. The latter term had actually been in use for some time to generically indicate thorny plants such as thistle or artichoke and on the occasion of the Melocactus discovery it was decided to keep it, simply by having it preceded by the terms “melon” (i.e. melon) and “ekinos” (i.e. “curly”, or “thorny”). It follows that the first Melocactus were classified as Echinomelocactus, a term later shortened to Melocactus. The first scientific descriptions of this kind date back to several centuries after the discovery, i.e. in the mid-eighteenth century and are by Carlo Linnaeus, botanist and “father” of modern scientific classification. In particular, Linnaeus described 22 species of Melocactus in his famous Species Plantarum, published in 1753. Over the years, many studies followed one another and today this genus has around thirty species in all.

A short description

Regardless of the species, Melocactus are plants with a globular habit, tending to become short-cylindrical with age. The stems are solitary and have no tendency to bunch or shoot, except as a result of trauma. The dimensions of these plants can be defined as medium and range from twenty centimeters in height of M. matanzanus (the smallest and earliest species to form the cephalium) up to one meter in height, without however counting the cephalium, which can reach about thirty centimeters in the oldest specimens. The stems are generally bright green to dark green in colour, but do not lack the bluish tinge typical of the azureus species. The bodies of the plants are divided into very marked ribs capable of thinning or expanding (“accordion”) depending on the quantity of water present in the stem. The spines vary according to the species: they form at regular intervals along the coasts, they are always pointed and never hooked, slightly curved downwards. In some species they can be robust and short, in others thin and up to ten centimeters long (M. ernestii). The color of the thorns is usually white, tending to gray over time (except in some species, where the spine is brown).

The analysis of the root system is interesting, probably this is the real weak point of these plants. The roots of Melocactus are usually underdeveloped, fibrous in the part close to the stem. Here is what George Thomson notes in his volume “Melocactus” published by Cactus&Co Libri (2009): “This means that even modest damage in the first few centimeters of the root can lead to the loss of the entire root“. And this could actually explain why, once the cephalium has formed, it is advisable to avoid repotting these cacti. Thomson observes again: “The roots are very sensitive and the plants lose them easily in case of prolonged periods of drought or in conditions of stagnant water”.

The cephalium

As we have seen, the cephalium represents the element that distinguishes this genus, although over time other genera of cacti also form what is called “false cephalium” (for example the Discocactus). In Melocactus the cephalium represents the watershed that separates the “juvenile” age from the maturity of the plant, i.e. the moment in which the latter is able to flower, produce fruit and therefore reproduce. Before the formation of the cephalium, the Melocactus develop the stem, which almost always takes on a short-cylindrical shape with age. The Melocactus produces offshoots very rarely and generally do so following an arrest in growth caused by a parasitic attack or, in any case, following a trauma sustained during growth, in particular at the vegetative apex. Once the adult stage is reached, after six or seven years in the earliest species (M. matanzanus) or after at least ten years in other species, the stem stops growing and the plant concentrates its energies on the production of the cephalium, which it forms at the apex of the plants and is composed of short, bristly and thick hair, usually red or white. From this moment on, only the cephalium will grow, which in some species reaches 4-5 centimeters (M. bahiensis), and in others it can reach twenty centimeters (M. peruvianus), giving the plant a bizarre appearance. Here is what George Thomson writes about it in the aforementioned “Melocactus – care and cultivation”: “It has been demonstrated that a large part of the stem of a mature Melocactus comprises only juvenile tissue with a transparent epidermis, and the adult tissue, without stomata, is mostly confined to the central nucleus of the cephalium. This juvenile tissue in the stem of melocactus is probably the reason why it is very difficult, though not impossible, to revive a plant that has lost its roots”.

It is from the cephalium that, during the summer, the flowers are formed, which are tiny in size and vary in color from pink to magenta, and subsequently  the fruits, which appear in the form of oblong, smooth, white, pink or red. The growth of the cephalium in height is annual and in some cases it is possible to observe the layers which make evident the annual development of this curious organism. Finally, in some specimens, it is possible to observe the dichotomization of the cephalium, i.e. its division into two distinct parts according to a phenomenon common to other cacti, in which the vegetative apex can divide (dichotomize precisely) and give life to two distinct “heads” (the phenomenon often occurs in Mammillaria parkinsonii, for example).

Cultivation

Fascinating, particular, bizarre but “touchy” plants, Melocactus are certainly not among the simplest cacti in terms of cultivation. Their life and consequently the level of cultivation can be divided into two phases: pre-cephalian and post-cephalian. Before the formation of the cephalium  the Melocactus can be treated exactly like most cacti and  also tolerate minimum winter temperatures close to zero Celsius degrees. Once the cephalium has formed, cultivation becomes more demanding: the plants no longer tolerate repotting, unless you simply remove the plant from the old container to gently insert it into a new pot without touching the roots (even in these cases, however, some specimens can go into stress and stop growth). Furthermore, since the plant has reached the adult stage, it is advisable  to avoid the winter cold and the Melocactus, from mid-October to the end of April, must be placed in environments sheltered from the rain and where the minimum temperatures do not drop below 15-16 degrees. They can also be placed in the apartment, in a bright place, but they must be watered in moderation no more than once a month and only to prevent the root system from drying out completely. If the stem does not show signs of suffering (in other words if it remains swollen and turgid) it is also possible to limit winter watering to once every two months, so as to further reduce the risk of collar rot.

As far as the substrate is concerned, whether the plant is still young or has a cephalium, the situation does not change and  the Melocactus need very draining and light soils. You can use the tested mix based on peat, pumice and lapilli in equal parts (possibly reducing the peat part and increasing the pumice or adding river gravel or quartzite), or you can create a substrate starting from common clay (a maximum of 20%) by adding a little sand, a little peat (10%) and for the remainder various inert materials such as pumice, gravel or quartzite.

No particular indications regarding  watering and fertilization: during the growing season, Melocactus (with or without cephalium) must be treated like most cacti, with regular watering every two weeks and three or four fertilizations at most. Finally, as far as exposure is concerned, these plants need a lot of light but not necessarily direct sun, which can burn or discolor the epidermis since the thorns are thick enough to protect it from the intense rays of the sun in July and August, especially between noon and 3 pm. A shaded greenhouse, a windowsill, a balcony or a terrace facing Southeast will be ideal and if the direct sun hits the plants throughout the day, it will be sufficient to place the Melocactus in the shelter of shrubs or large plants.

Sowing

The sowing of these cacti is simple and also suitable for those who intend to practice. The fruits are produced autonomously by the plants and emerge from the cephalium during the summer. It is sufficient to extract them by gently pulling the “petiole” formed after the flower has dried, but be careful: it is advisable to wait until the plant has expelled the fruit for at least half of its length. The berry must be able to slip off without any effort; otherwise it should be left in place because tearing the fruit would put the plant at risk, which would end up with a broken and moist berry inside the cephalium (actually, a gateway for pathogens and bacteria). Once the berries have been removed, they are left to dry for a few weeks, then they are opened and the round, black and small seeds are extracted. The sowing procedure is the same that we adopt for almost all cacti (the seeds do not require any  treatment) and growth during the first few years is not particularly slow. With the matanzanus species, for example, 7-8 years are “sufficient” to obtain plants with cephalium.

Main problems

Overall, Melocactus are quite robust plants and if well cultivated they are not subject to adversity in a different way than other cacti. They are certainly  particularly sensitive to water stagnation, especially in winter, therefore it is advisable, with these plants, to always have a light hand when it comes to watering. A phenomenon that frequently affects Melocactus (and which can happen with any cacti, albeit less frequently) is the loss of the root system. Often, even without apparent causes, in the absence of parasites and without having repotted, the roots of Melocactus go into “tilt”. It almost always happens with specimens equipped with cephalium and when we realize it, it’s too late to intervene: the stem dehydrates, deflates and despite watering it does not regain volume. The problem is that a plant with a cephalium seems almost incapable of reforming its root system. In other words, no matter how much care we give to the specimen (flaring it, cleaning the roots, removing the dry ones, placing the plant on pumice), the touchy Melocactus always seems to prefer a slow agony rather than reforming the roots and starting again, as does the most cacti. The sad consequence is that the specimen can remain alive even for two or more years, until the water reserves accumulated inside the stem are completely consumed…

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Correlated articles

Culivation cards in pdf
How to save a cactus without roots
Cacti and succulents: seasonal care
Distribution of cacti and succulents: maps
Growing with Seramis

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L'articolo How to cultivate Melocactus, cacti that with age put on… the hat (“cephalium”)! proviene da Il fiore tra le spine.

Cacti are plants that have made drought resistance their strong point. These are “xerophytic” or “xerophilous” plants, i.e. plants capable of accumulating water reserves for surviving in arid and semi-desert environments. If this is the rule, there is no lack of exception, which is represented by the epiphytic cactaceae. We are still in the Cactaceae family, but these are very particular genera, starting from their habit, which thrive in rainforests and which in sub-desert areas would not be able to survive. Epiphytic cacti are widespread on the market and in cultivation, just think of the Epiphyllum genus, but they have particular and very different needs compared to most cacti, starting from the substrates, passing to the water regime and to the exposure. And this is why it is important to know which genera of cacti belong to the “epiphytic branch”: because in cultivation we will have to ensure very different conditions for these plants compared to those we can – and must – guarantee for genera such as Ferocactus, Echinocactus, Ariocarpus, etc.

In this article, therefore, we see what the epiphytic genera are, what their needs are and how they should be cultivated (…).

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L'articolo What are epiphytic cacti and how to cultivate these plants native to rainforests? proviene da Il fiore tra le spine.

It’s a bit like that shy and reserved distant relative: everyone in the family knows he exists, but little or nothing is known about him, or his history. Those who grow cacti and succulent plants, those who are used to attending market-exhibitions of succulent plants, those who hang out in well-stocked nurseries, have certainly observed more than one specimen. Many enthusiasts have one or more specimens in their cacti collection. Yet, very little is known about this Echinopsis Haku-jo. In the many texts dedicated to cacti (not only in Italian) the plant often appears in photographs but the information is always scarce; online there are only brief synthetic cards, almost always accompanying the specimens for sale. For the rest, nothing. The history of this cultivar (a plant that does not exist in nature but obtained through hybridization and crossbreeding by man) remains shrouded in mystery.

In this article I try to summarize what I have learned in years of cultivation and what I have managed to learn about this intriguing Echinopsis cultivar, whose flowering is among the most bizarre in the whole family of cacti (…).

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L'articolo Echinopsis Haku-jo, the cactus with mysterious origins: it does not exist in nature but it’s very popular on the market proviene da Il fiore tra le spine.

Living tangles of incredibly intricate spines, “globes” wrapped in beautiful, deep yellow spines. This is how Ferocactus johnstonianus could be defined, perhaps hastily but at the same time realistically. We are talking about one of the most appreciated and sought after species among enthusiasts of the Ferocactus genus throughout the world. These are relatively uncommon and poorly propagated plants, not easily available on the market. They also do not grow quickly, and perhaps these are some of the factors that contribute to fueling the charm of johnstonianus. In these days of repotting I have had the opportunity to focus on some specimens of this species that I received a few years ago from my friend Francesco Soldi, a highly experienced italian grower especially with regards to the Ferocactus genus, although today he is concentrating on the Echinocactus genus and in particular on the horizonthalonius species. Well, the plants I got from him a few years ago initially grew very slowly – mostly my fault, because I put off repotting for a long time and used an excessively poor substrate – but in the last two years, also thanks to a slightly richer substrate, have recovered and today they are well characterized and proportioned and are starting to show their full potential.

In this article here is an in-depth look at this splendid species. (…)

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L'articolo Johnstonianus, the most beautiful and sought after species of the entire Ferocactus genus proviene da Il fiore tra le spine.

Keep on reading the article if you want to know how this story goes (…)

Well, if on the one hand, I would still like to see my expression immediately after having smelled that flower, on the other hand, the joke of that nurserywoman has forever imprinted in my memory my first encounter with a Stapelia (in this case a Stapelia gigantea), but above all with its flower, as beautiful and showy as it’s terrible, disgusting in terms of smell. And on the other hand, this is the main characteristic of almost all the plants belonging to the Asclepiadaceae family: their flowers, be they the small ones of the Piaranthus or the huge ones of certain Stapeliads, have a terrible smell. The smell they give off is that of rotting flesh, in particular, and there’s a specific reason Nature has chosen this for them.

Let’s see why this large family of succulents is condemned to produce flowers with beautiful shapes, incredible streaks and yet terribly smelly. Let’s get to know better the Asclepiadaceae, the various genera belonging to this family native to Africa and let’s learn how to correctly cultivate its species.

Origin and provenance

The Asclepiadaceae family includes about two thousand species and almost 250 genera, a quarter of which are succulents. In the last years, the classification has changed the Asclepiadaceae family to a subfamily included in the Apocynaceae family, but for convenience and brevity, I will write here of “family” referring to the Asclepiadaceae. First of all, it must be said that not all Asclepiadaceae are succulent plants: in this large family, you can find herbaceous plants, leafy plants, bushes, trees and even lianas. The origin of these plants is mainly African, in particular the temperate, tropical, subtropical and desert regions of the African continent. However, their distribution is not limited to Africa: some genera of the Asclepiadaceae family are native to the American continent, others to the Arabian Peninsula to China, and others to Oceania. Finally, two species are of European origin: Caralluma mumbyana and Caralluma europaea, actually native to the extreme South of Italy (Lampedusa) and North Africa (Morocco, Tunisia, Libya).

Maps with the distribution of succulents in the world.

Flowers are of various sizes and go from the few centimetres of Hoya to the huge ones, up to about thirty centimetres, of Stapelia gigantea, but they are always star-shaped, with five sepals and five petals joined together at the base.

The most known and cultivated genera

As for the lovers of succulent plants, the most appreciated and cultivated Asclepiadaceae belong to the group (or “tribe”) of Stapeliae. In this group are included: the genera Stapelia, Caralluma, Duvalia, Echidnopsis, Frerea, Hoodia, Huernia, Orbea, Piaranthus, Pseudolithos, Tavaresia, Whitesloanea. Among the Asclepiadaceae not belonging to the Stapeliae group, more cultivated by the lovers of succulents, there’re Hoya (the epiphytic plant with “wax flowers”), Ceropegia and Fockea. The species of the group Stapeliae are almost all characterized by fleshy stems and tufty posture. In some cases, they develop proper succulent branches, in others, they form rounded or short-cylindrical “articles” (as with the genus Piaranthus). In other cases, the stem is like a sculpture, similar to a small monolith or a rock (e.g. Pseudolithos and Whitesloanea). Totally different is instead the posture of Hoya, which develops very long stems from which fleshy, thick leaves come out. Ceropegia has a similar appearance, while Fockea forms big brown caudex (caudex is basically the thick and wide stem) from which long branches with small, not fleshy, leaves of an intense green colour branch out.

Why do the flowers smell?

Let’s start by saying that not all the flowers of the Asclepiadaceae deserve the nickname of “carrion flower” or “stinky plant”, with which Stapelia flowers are usually associated. Many flowers of plants belonging to this family produce perfume or ugly odour, as in the case of Hoya, whose flowers grouped in clusters have a beautiful shiny appearance, perfect, to be defined as “of wax”. Same for the flowers of Fockea, not very evident and without any particular smell or fragrance. They certainly deserve the definition of “carrion flower” many other genera, almost all belonging to the group Stapeliae, particularly the flowers of Stapelia and those of Piaranthus.

Why this curse? Why do such showy, beautiful and colourful flowers give off the smell of rotting flesh? Simply because the pollinating insects of these plants are flies, and it’s to these insects that these plants rely on to multiply. The most emblematic example is Stapelia hirsuta (the plant you can see above, under the title), which produces large star-shaped flowers, blood-red in colour to recall the colour of meat, and smelly, just like rotting flesh. The flies are strongly attracted to it: they pass from one flower to another just as bees do with any flower, pollinate the Stapelia and lay their larvae inside the flower, which, however, drying up, will prove to be a deadly trap for the larvae themselves, condemned to die inside the closed flower. If the smell of rotten meat is typical of the species of the genus Stapelia, many other Asclepiadaceae produce smell even if with different “fragrances”, as in the case of Piaranthus, Orbea and Pseudolithos, just to mention a few. Finally, as for the flowering period, almost all the Stapelia‘s plants group flower in autumn until the beginning of winter. An element, this one, which can interest those who want to enjoy blooming for almost the whole year, if they place side by side to the cultivation of Cactaceae the cultivation of Asclepiadaceae.

Cultivation regime

Staying in the Stapeliae group, which is of interest to succulent growers, it should be noted that Asclepiadaceae need a very different cultivation regime than the one effective for Cactaceae. Firstly concerning the minimum winter temperatures, which should be kept under control so that Asclepiadaceae do not go down 7-8 Celsius degrees. Fundamental, as for cacti, is that the plants remain in full dry soil from October to the end of March. If we see that the stems begin to lose too much turgidity, we can give little water on sunny days. I recover my Asclepiadaceae in an unheated cellar, with minimum temperatures between 6-8 degrees. At night, in the greenhouse, it can go down to 0 degrees, and I prefer not to risk it. Even about the exposure, the differences with most of the Cactaceae are of relief. The Asclepiadaceae of the group Stapeliae do not go exposed to the direct sun if not in the morning. From when the sun gets warmer, around midday, the plants should be sheltered in a greenhouse or by a shading net or, again, placed behind plants and shrubs that can give them shade. If kept in too much sun, Stapeliae suffers, slow down their vegetation and become extremely red. In summary: give them lots of light but not direct sun.

Watering should be done only from the end of March to the end of October but without exaggerating because these plants are sensitive to water stagnation and environmental humidity. Watering should be reduced, therefore, and the soil should be very draining. About the substrate, some grow Asclepiadaceae succulents in mineral soil, without organic (peat or humus), mixing pumice, zeolite, akadama, gravel, etc… Other growers keep them in only pumice, which promotes rooting and retains excess water by releasing it little by little. I’ve been growing these plants in the usual mix of equal parts peat, pumice, and lapilli, but I’m gradually switching to pumice alone, which requires more frequent fertilizing because it doesn’t provide much in the way of nutrients. Alternatively (as I did in the video at the end of this article), you can use a substrate made of pumice with the addition of a few humus (10%) and not much sand to give a minimum of nutrients and to add a good part to the compost, which with only pumice would be too coarse.

The soils to use with succulent plants.

In his book, Giuseppe Lodi advised to grow the Asclepiadaceae “in rather oily soil, but very permeable and sandy at the top”. He suggests it just to ensure that the collar does not remain wet for too long, being easily subject to rot. Always noted Lodi: “It is advisable to put a rich layer at the bottom (more leaf mould than sand and soil), then an intermediate layer with more sand and an upper one even more sandy” (Giuseppe Lodi, “Le mie piante grasse” – Edagricole).
For the rest, the cultivation rules indicated for most succulents are valid: as much air as possible and sparing fertilizations with specific products for succulents only during the vegetative season.

Main adversities

Collar rot and cochineal mealybug are the main problems in the cultivation of succulent Asclepiadaceae. To preventing rottenness, it’s advisable to moderate watering, use correct substrates and give as much air as possible to our plants. Against mealybug, the same cares are more or less valid since proper cultivation is the best prevention. Also, as a preventive measure, it’s possible to use specific products in particular periods. A few passes of copper oxychloride by spraying the stems at the end of the growing season and just before spring, for example, and Neem oil, again by showering during the warmer months (here a specific article). Against mealybug, some recommend inserting two or three balls of mothballs in the soil, a little deep. I have never tried this method, but I have heard of it several times.

Propagation

The multiplication of Asclepiadaceae can be done, as always, by seed or by cuttings. Seeding is necessary for those kinds of plants that do not branch, such as Trichocaulon and Whitesloanea, while cutting is the fastest method to reproduce genera such as Stapelia, Orbea, Caralluma, etc… It’s enough to cut a branch with a sharp cutter, let it dry for a couple of weeks in an airy place, sheltered from the sun and then place it on pumice with a superficial layer of sand. At that point, it’s possible to nebulize the stem and the substrate’s surface once every two or three days, thus favouring the rooting of the cutting. Obviously, reproduction by cuttings must be done during the vegetation period, therefore from late spring onwards and never in winter. Moreover, to avoid rottenness, it is better to sprinkle with copper oxychloride powder both the mother plant in the point where the branch has been cut and the cutting itself.

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Repotting of Asclepiadaceae: the video

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L'articolo The Asclepiadaceae family: African succulents with beautiful but… smelly flowers proviene da Il fiore tra le spine.

In the following article we see in detail where it comes from, what are the cultivation needs of this succulent, what are its weaknesses and how it can be successfully reproduced even by those who are beginners in the cultivation of succulent plants. (…)

Description

Crassula ovata belongs to the large Crassulaceae family (also known as the “Borracina family”), made up exclusively of succulent plants. It is the third family in the world in terms of number of species and genera, immediately after that of the Cactaceae and that of the Mesembreyanthemaceae (now Aizoaceae). Just to give a few examples, the Crassulaceae family includes widespread and appreciated genera such as Aeonium, Adromischus, Cotyledon, Echeveria, Graptopetalum, Kalanchoe, Pachyphytum, Sedum and Sempervivum.

Understanding plant classification: a specific article.

With such a wealth of genera, it is not surprising that the Crassulaceae family is widespread in all continents, with the exception of Antarctica, and the plants attributable to it have adapted over the years to conditions of all kinds, from the ones offered by subtropical and tropical areas up to the mountain areas of the Alps (Sempervivum, for example).

Maps with the distribution of succulents in the world.

The Crassula genus includes between 250 and 260 species, almost all with thick, fleshy leaves. We can have Crassulas of all shapes and sizes, from herbaceous annuals to arboreal perennials. The provenance of this genus is predominantly African, in particular the southern area of the African continent. The ovata species is probably the best known and most widespread of the entire Crassula genus: it can be seen in cultivation almost everywhere in houses, on windowsills, terraces and gardens. It seems that it has been habitually cultivated as an ornamental for at least a couple of centuries. Once classified as Crassula portulacea, over the years the Crassula ovata forms real saplings which in habitat can reach two and a half meters in height, with very thick and robust brown central trunks, loaded with the characteristic intense green leaves , edged in red if exposed to full sun, which emerge from the many ramifications.

If we grow this plant in sheltered and not very bright environments we will have dark green leaves, while if we expose the already well-formed plants to direct sun we will have light green leaves with a beautiful red border. But be careful: from what I have been able to ascertain, these are plants that should be kept in direct sun only for part of the day. Too many hours of sun risk inhibiting its growth and excessively lightening the leaves until they become yellowish. On the other hand, the cold also contributes to a chromatic variation, which leads the leaves to take on a reddish color over the entire surface.

Cultivation

The cultivation of Crassula ovata is decidedly simple and also suitable for beginners. The plant, as mentioned, has a high adaptability and tolerates many of our mistakes. It can be kept in the apartment or in closed places, as long as it is near a bright window, as well as outdoors in full light for a few hours (preferably in the morning until noon).

The suitable substrate can go from the common mix based on pumice, lapillus and peat in equal parts, to a soil a little richer in organic matter (even 50% peat and 50% various aggregates). Clay is also suitable, provided that a good part of organic matter is added (at least 30% peat or earthworm humus) and aggregates such as gravel, sand, pumice. In summary, the soil must be richer than the one we use for cacti but still loose and draining, able to dry in a few days.

Watering can be frequent and abundant (even once every two or three days in the warmer months) in the growing season and heavily spaced in the autumn and winter months if we keep our Crassula in cold environments. I keep my specimens in the greenhouse with low night temperatures around zero degrees and from November to March, for example, I limit myself to wetting them in moderation only when I see that the leaves begin to wrinkle. If, on the other hand, we grow Crassula at home, in winter it is good to water a few more times, but always in moderation because the plant slows down the vegetation anyway.

As far as temperatures are concerned, I have seen that if the Crassula spend several nights below zero it is easy for them to start to deteriorate and lose their branches. I guess it’s a defense mechanism that leads the plant to sacrifice the “periphery” to safeguard the “center”. It has happened to me several times, in the past years, that I have had to intervene by cutting cleanly dried branches during the winter, until I have almost completely pruned the plants. Over the course of a growing season, the central part emits new branches and new leaves and returns to full shape, but it is clear that to have large specimens it will take much longer. For some years now I have kept my Crassula in the greenhouse but covered by a couple of layers of non-woven fabric, so that the temperatures do not drop below two or three Celsius degrees on the coldest nights.

The growth of these succulents is relatively fast and, if you water and fertilize regularly during the growing season, within a few years from a simple twig we will have a beautiful shrub which we can also give a tree shape with appropriate pruning (to be done in late spring).

Flowering

Flowering is winter: generally, in my area (Northern Italy) between the months of November and December. The flowers are small, white and with some pink hues, but all in all inconspicuous. They are very simple and decidedly unattractive when compared to those of other succulent plants, and are collected in inflorescences supported by thin stems that emerge from the grafting of the leaves. The flowers of these plants last a few weeks and this is also thanks to the low temperatures that characterize the flowering period.

Reproduction

The reproduction of Crassula is very simple and is done almost exclusively by cuttings. In spring, it is sufficient to cut a well-formed branch with a garden shears and let it dry in a shady place for a couple of weeks and then plant it for a few centimeters in very sandy soil (or rich in pumice). For the first two/three weeks it will be sufficient to nebulize both the leaves and the surface of the soil every day, then the substrate can be moderately wet directly. A month later, if we see new leaves appearing, it will mean that the cutting has rooted and we will be able to slightly increase the frequency of watering. The following year it will be possible to repot the new plant in a larger pot and in a soil richer in organic matter. Leaf cuttings can also be made, substantially with the same procedure described above, but I have never tried it directly since the branch cutting obviously ensures much faster development times for the new plant.

Pests and diseases

Crassula is a robust and rustic plant. This does not mean that it doesn’t have its own weak point: in fact it seems to be particularly appreciated by the cottony cochineal, which nestles among the leaves and on the branches, sucking the sap from the plant. For this reason it is always good to keep our specimens under control and, if we identify the cochineal, intervene immediately. If the attack is still contained, it is sufficient to remove the insects with a toothpick, but if the attack is massive, the plant must be immediately isolated and treated with specific products.

Other varieties

Crassula ovata can come in several forms, including some man-made cultivars. The most common variant is the “monstrous” Crassula, also known as the “hobbit” Crassula. It differs from the typical shape for the leaves, which are not wide and flat but almost cylindrical and resemble green “tubes” with reddish ends. The cultivation of the “hobbit” form does not present particular difficulties and is substantially identical to that of the traditional ovata.

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Correlated articles

Succulent plants
Substrates for cacti and succulents
Watering succulents
Classification of succulents

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L'articolo Crassula ovata, “Jade Tree” or “Money Plant”: here’s how to grow this beautiful succulent proviene da Il fiore tra le spine.

This peculiar cactus has a debatable scientific name and a slew of common ones.  Echinocatus texensis is an extraordinary cactus, not very well known, and relatively uncommon in cultivation, yet it possesses all the characteristics that make a cactus well-worth growing.  These include its compact and rounded appearance, robust and colourful spines, beautiful blooms, resistance to drought and high tolerance to direct sun as well as tolerating low winter temperatures.  In addition, it has very decorative deep-red fruits (some of the most beautiful among cacti) and a relative simplicity of cultivation combined with a high predisposition for using the “wild” technique.  This means reproducing, as much as possible, the conditions that cacti grow in their habitat, and paying attention to the substrate, direct exposure to the sun, very spartan cultivation, etc.

Origin and habitat

Echinocactus texensis (or Homalocephala texensis according to the original classification by Britton and Rose) is a cactus native to the south-eastern United States, particularly in New Mexico, southwestern Oklahoma and a good part of Texas (hence the name given to this species).  It also grows in some Mexican regions, particularly in the north-eastern areas of the Sierra Madre, in Coahuila, Nuevo Léon, and Tamaulipas states.  According to some sources, this species also grows in Chihuahua, Durango and Zacatecas. E. texensis grows from near sea-level up to 1,000m in very heterogeneous sub-desert areas: from xerophilous (arid) scrub to grasslands, broad clearings in forested areas, plains, valleys, and low hills. This indicates that the soils into where E. texensis sinks its roots can be highly variable, but are primarily calcareous and sandy. One thing is certain, and that is that this cactus almost always grows hidden among grasses or in areas where there is some vegetation consisting of bushes and small shrubs.  The presence of shrubs and grasses indicate a substrate richer in organic matter than that in which some other cacti thrive (eg Ariocarpus and Pelecyphora).  Dying and decomposing as an effect of short life cycles resulting from the aridity of these regions, the grasses enrich the organic component of the soil, and provide nutrients that would not otherwise occur.  We therefore need to bear in mind then that in cultivating E. texensis we should think about using substrates that are not too poor in organic material, in particular with young specimens.

Classification and common names

If the scientific name is debatable from the point of view of classification, namely Homalocephala texensis or Echinocactus texensis, then common names abound.  In the US, where these plants grow, they are called Candy Cactus, Devil’s Head Cactus, Devil’s Pincushion, or Horse Crippler.  In Mexico, E. texensis is also commonly called Mancacaballo, Monco Caballo or Viznaga (Anderson, 2001: 227–229). Regarding its scientific classification, for many years this plant has been included in the genus Homalocephala by Britton and Rose, where it contained just one species, H. texensis.  Later on, several authors decided to eliminate the genus Homalocephala and move the species texensis into the genus Echinocactus, together with the species grusonii, platyacanthus (ingens), horizonthalonius, parryi and polycephalus. In recent years, reopening the debate, many researchers believe it is appropriate to restore the genus Homalocephala, including the species texensis, parryi and polycephalus.  In support of this, a study by several authors (Vargas-Luna et al, 2018), address the issue from a genetic point of view.  In the introduction, the authors argue, “…we propose to recognize a monophyletic Echinocactus and a monophyletic Homalocephala as two distinct genera with their molecular and morphological synapomorphies”. In summary, if we follow their work, the genus Echinocactus will contain only the species grusonii, platyacanthus and horizonthalonius, and the genus Homalocephala will include texensis, parryi and polycephalus.

To further complicate our lives, we find that in the original genus Echinocactus there were four taxa: E. polycephalus subsp. xeranthemoides, E. polycephalus subsp. polycephalus, E. horizonthalonius subsp. nicholii (L.D. Benson) and E. horizonthalonius subsp. horizonthalonius (Coulter, 1896, Benson, 1969).  Strictly speaking, accepting the new distinction, the two E. polycephalus taxa would now be considered to belong to the genus Homalocephala.

Description

Echinocactus (or Homalocephala) texensis is a solitary plant that does not offset, even in old age (unless it has suffered damage to the growing point).  The formative stem shape is globular, but with time it assumes a flattened shape, depressed at the apex.  In nature, the body can be up to 20cm high, with a diameter of about 30cm.  The stem is divided into very pronounced ribs with a thin, sharp edge; in adult specimens, the number of ribs varies from a dozen to 25, Anderson (2001) records 27, and Lodi (1997) 25.  The body colour is light green or dark green (during the winter, it can redden, especially along the ribs) and the areoles, from which the spines appear, are quite widely spaced.  In young specimens, the areoles are woolly, a detail that is common to all Echinocactus, at least in their development phase.

The spines, initially thin and weak, become wide, thick and very strong.  In adult specimens, there are six radial spines (Lodi notes 6 or 7 of them) up to 4 or 5cm in length, and a central spine up to 7cm long (exceptionally even more), thick and broad, flattened, sharp and slightly curved downward at the end. Some may have a short, thick central spine. I think this variability may be determined by a genetic response to local conditions. New spines are red, but they tend to fade to pink, greyish and almost white lower down.  The spine surface shows transverse ridges that testify to the age of the plant.  They are velvety to the touch, and when wet, the spines of E. texensis take on a brilliant, showy, bright-red colour. The phenomena of longitudinal ‘splitting’ of the central spine is sometimes observed in E. texensis, in effect producing a forked central spine. I have observed this in photos, but it has never happened in my collection.

Flowers, fruits and seeds

The flowers of E. texensis are pale pink to white, with a red or orange throat, and emerge at the apex in spring, usually around April.  The corollas can reach a diameter of 5–6cm, and the tepals have the peculiarity of terminal fringing. The yellow stigma lobes provide a handsome contrast.  The aspect and consistency of the flowers are reminiscent of silk.  I am not aware that the flowers are self-fertile (ie able to pollinate themselves).  Nevertheless, I have noticed that both pollination and the consequent formation of the fruit are very easy. The fruits, which form from the end of May, are very large and showy (up to 3–4cm in diameter and 4–5cm long), fleshy, and at the same time extremely firm in texture.  They are bright red and have smooth skin interspersed with small scales.  According to some authors, the fruits are edible, and because they are (or were) utilised for producing candies, these plants are also called Candy Cactus.  However, I do not have any direct evidence of this, and the definition of Candy Cactus could be simply due to the appearance of plants with ripe fruits, which can resemble small sweets. The seeds are medium-sized, not as large as those of Opuntia, for example, but easily handled, oblong and black in colour with a shiny cuticle.

Cultivation

The cultivation of E. texensis is easy enough, much like all species in the genus Echinocactus, with the exception of E. polycephalus, which is regarded as difficult and not recommended for the less experienced.  In over twenty years of growing E. texensis I have noticed only one problem, which is that this plant seems to be inclined to lose its roots much more easily than other cacti.  In my opinion, it may be due to environmental stress or using the wrong potting soil. Over the years, I have experimented with different soils for E. texensis, from purely mineral substrates to mixtures richer in organic matter (peat or earthworm humus).  The results indicate that these plants need a fair amount of organic matter in the substrate, not only when they are still seedlings but also as adults. It is no coincidence that the best results have been obtained by growing E. texensis in a mix of equal parts of pumice, grit and peat.  I had mediocre results with potting soils made of field soil (loam), aggregates such as pumice, and a small part of peat or humus (maximum 10%).  I have never experimented with marl (a type of fine clay) with these plants, but I do not rule out trying it as soon as possible in percentages not exceeding 50% and with the addition of at least 30% organic material. E. texensis, like all Echinocactus, need lots of light. As the plants reach at least three or four years old, from the end of March, they will benefit from being gradually introduced to full sunlight. Proper exposure will go a long way toward forming strong spines and keeping the body low and compact.

As far as temperatures are concerned, these cacti are very tolerant and resistant.  They can easily stand the blazing sun with more than 40°C, provided they are kept outdoors and have plenty of air movement.  During the European winter, if kept completely dry from late September, they can go well below freezing without damage.  I had specimens that have spent a few nights at -10°C and, except for a slight reddening of the epidermis, which disappeared with the arrival of spring, they did not suffer any damage.  According to some sources, E. texensis can withstand temperatures as low as -18°C, but I have no direct experience of this. The watering and fertilising regime does not differ from that of most cacti.  I give plenty of water in the growing season, from April to September, as long as the soil has time to dry between watering, and no water at all from the end of September to the end of March.  Some recommend watering E. texensis lightly, but even using potting soils with 30% organic content, I have never experienced rot, even with heavy watering.  I keep several specimens outside the greenhouse, which have experienced a week’s worth of rain on several occasions with no loss of life or damage.

All my plants, including E. texensis, receive a low-nitrogen cactus fertiliser a couple of times a year during the growing season as the slightly more organic substrate which I use already helps provide some nutrients. I have noticed that E. texensis comes into growth quite early, at least here in Northern Italy, starting from the end of February, when they begin to produce new spines.

Propagation

The only way to reproduce this species is by sowing seed, since they do not produce offsets.  The procedure is probably easier when compared to the sowing of some other cacti by the fact that the seeds of E. texensis are easy to handle because of their larger size.

According to most growers, E. texensis seeds do not need any special treatment, such as scarification, which is necessary or strongly recommended to germinate Echinocactus horizonthalonius, E. parryi and E. polycephalus.  From my experience, E. texensis seeds germinate well without any treatment.  However, some growers suggest that scarification could further increase germination if done correctly. I have always sowed E. texensis in natural light and heat, in April, without any particular procedure, except to soak the seeds for 24 hours with the sole purpose of hydrating them and softening the cuticle, which seems to me to be quite leathery.  I am planning some experiments with both scarified and non-scarified seeds, having many at my disposal originating from plants grown under the same conditions.

How to sow cacti and succulent plants.

Literature

• Anderson, E. F. (2001) The Cactus Family. Timber Press.
• Lodi, G. (1997) Le mie piante grasse. Edagricole. pp 75–76.
• Vargas-Luna, M D et al (2018) Splitting Echinocactus: morphological and molecular evidence support the recognition of Homalocephala as a distinct genus in the Cacteae. PhytoKeys 111: 31–59.
• Vermeulen, N. (1999) Cactus. Idea Libri Srl. pp 56.

Correlated links

Cultivation cards in pdf
Knowledge and curiosity
Echinocactus grusonii: a little history
Wild cultivation

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L'articolo Echinocactus texensis, an in-depth study of the “horse crippler” proviene da Il fiore tra le spine.

Let’s deepen our knowledge of the Lithops genus in this article, in which we will also see the particular cultivation regime that these plants need in order to live in the Northern hemisphere. (…)

Description

Among the genera belonging to the Mesembryanthemaceae (or Aizoaceae according to the classification currently accepted by the majority of researchers), that of the Lithops is certainly among the most full-bodied in terms of number of species and at the same time among the most appreciated in cultivation. These are dwarf plants, ie small even in adulthood, coming from semi-desert areas of southern Africa, in particular from the areas of Namibia and South Africa. The “living stones” are called by Giuseppe Lodi in his splendid volume “Le mie piante grasse” (Edagricole). And “living stones” or “living rocks” is the definition to which we often see these plants associated, due to their flat, rounded appearance, with colors and superior design capable of perfectly reproducing small stones, with which in nature they are camouflage on the soils of origin. On the other hand, the same scientific name indicates this characteristic, being derived from the Greek lithos, i.e. pebble/stone, and opsis, i.e. “appearance”.

Each plant is formed by a pair of fleshy leaves, joined at the base of the short conical stem and clearly separated by a slit at the apex, which is flat and with rounded edges, overall ovoid in shape. If along the sides the stem and the leaves have a uniform colour, which varies from species to species from green to reddish to grey/blue, the upper part of the leaves, i.e. the one that receives light and stores it for photosynthesis, is covered by thin veins (in some cases there are punctiform spots) and rich in shaded colours, these too vary according to the species. The stem is almost completely underground: the plants emerge from the ground for a few millimeters and the upper face of the two leaves has a sort of “window”, i.e. an area without chlorophyll and therefore able to filter the light and let it penetrate inside the plant. The root system develops at the end of the cone which forms the stem and branches off from a fleshy root, dividing into not particularly long peripheral roots. Overall, however, between the stem and the root system, the plant grows several centimeters deep and it will therefore be a good idea to use deep pots for cultivation.

The flowers

Lithops blooms are never abundant: generally one or two flowers at a time, but if we grow these plants in bowls, side by side, we will have a beautiful spot of color during flowering, which in our latitudes (Northern hemisphere) occurs in autumn roughly between the end of October and the beginning of November. The flowers emerge from the crack between the two leaves and are always white or yellow, reminiscent of daisies and open in the afternoon. In this regard, what Lodi notes is interesting: “The difference in color of the flowers is often accompanied by a difference in the shape of the bodies. In the very young plants of Lithops with yellow flowers (…) the fissure between the two lobes does not cross the entire upper face; in those with white flowers (Leucolithops) the fissure crosses the entire upper face” (Giuseppe Lodi, “Le mie piante grasse”, ed. Edagricole).

The moult of the leaves

A peculiar feature of these plants is the moulting of the leaves, which can occur in variable periods (in any case during the winter in the northern hemisphere) depending on the species and age of the plant. It is through the moult that the plant, in fact, is “reborn” and perpetuates itself. The old leaves dehydrate to get completely dry; at the same time, a new pair of leaves begins to form from the buried stem. As they grow, the new leaves will literally break the old ones, which will have collapsed in the meantime. Once the new ones have formed, the old leaves will dry out completely and can be detached by simply pulling them gently with your fingers (operation to be done only when the leaves are completely dry!). Of fundamental importance is not to water the plant while the moult is in progress. In this phase the Lithops do not absorb water and the new leaves feed on the liquids accumulated inside the stems. Watering would be equivalent to soaking the soil so that it remains wet for a long time (in part because the moult takes place in winter and the humidity does not evaporate due to the low temperatures, in part because in this phase the plant does not drink), with consequent triggering of the rot that would lead the plant to death.

Cultivation

The cultivation of these plants requires particular and distinct precautions compared to those required by cacti or other succulents. Overall, however, Lithops are not difficult to grow, provided you know their needs.

The soil must be very poor and draining. You can use a third of clayey field earth mixed with fine sand to which we will add a third of pumice and a third of quartzite (that for aquariums is fine). Alternatively, we can reduce the part of clay a little to add a small organic component (peat or earthworm humus). Lodi advised, for these plants, a substrate composed of three parts of sand, two of clay and one of leaf mold. As far as exposure is concerned, Lithops need plenty of light, even direct sun if they are used to it, for most of the day. In this way they will maintain the compact shape of the stem and the leaves will not lengthen, ending up protruding a few centimeters from the soil, as happens in incorrectly cultivated specimens.

The waterings can be abundant but it is good to reduce them and wait for the substratum to dry completely between one watering and another, also because these succulents are particularly sensitive to humidity and can rot easily if the soil is not correct. On the contrary, like many other Mesembryanthemaceae, they tolerate long periods of drought without problems, so in case of doubt, the advice is always to not water and let more time pass before giving water.

As a rule, let’s say that in the Northern hemisphere the Lithops are watered exclusively from May to all of October, reducing the watering in the central months (July and August) to suspend them completely in November: in fact, they should be watered from when the moult is completed until the plants slow down to face the winter. During the winter months it is not entirely certain that these plants go into stasis, as happens for example with cacti. It is probable that, even if they stop absorbing water, the plants work on moulting in the underground part. No problem with low temperatures: if kept perfectly dry from the end of October, Lithops can winter even at five or six Celsius degrees below zero.

Reproduction

Lithops can be reproduced by cuttings or by division of the tufts, but the most used method is sowing, which follows the rules common to cacti. The seeds are rather small and the undertaking can prove inconvenient for the less experienced, but overall it does not present particular difficulties.

Species and varieties

There are dozens of species attributable to the genus Lithops and even more varieties. Only an expert eye is able to distinguish one species from another or a variety from a cultivar. The design on the leaf surface can help, as well as the color of the plant and its nuances, but the undertaking, for those who are not experts, remains quite difficult. Among the most common and widespread species we should mention the aucampie, the karasmontana, the lesliei, the optica and the pseudotruncatella. As for the colors you are spoiled for choice and there is no shortage of bright green Lithops (once very difficult to find) or blue, gray, brick red or purplish.

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Succulent plants
Substrates for cacti and succulents
Watering succulents
Classification of succulents

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L'articolo Lithops: peculiarities and cultivation rules of the so-called “stone plants” or “living stones” proviene da Il fiore tra le spine.