The main factors we need to take into account are:
When we have learned about these factors, we will be able to apply this knowledge to the requirements of cultivation:
Turbinicarpus species grow in the north eastern and central parts of México, consisting of the, mainly desert, states of San Luis Potosi, Nuevo Leon, Hidalgo, Tamaulipas, Queretaro, Coahuila and Zacatecas. As you can see, the distribution for this relatively small genus is quite large. However, each species is generally only found in small isolated areas. This area of México is characterized by high light levels and fairly low amounts of rainfall.
The types of soil the plants are found in are obviously a major factor that we must take into account. The soil characteristics we need to look at include the composition of the soil, with regard the relative amounts of organic and inorganic components, drainage characteristics and pH.
The localities that these plants grow in vary from steep hill sides, on which the plants can be found in cracks in the rocks where humus has collected or in areas where larger amounts of soil has collected, to large areas of level ground. Most of the species grow in soils with low amounts of organic matter and large amounts of sand/grit/gravel, of various forms, which provides a very well drained soil. This drainage component generally consists of limestone gravel, but there are also species that grow in soils consisting of gypsum, e.g. T. lophophoroides, hoferi etc. In many localities these plants are found growing in pure gypsum. The particle size ranges from small sand grains (to 2mm Ø), to large slabs of rock reaching 20 cm Ø. Having limestone or gypsum as the major constituent also results in the pH being on the slightly alkaline side, generally between 7.1 to 8.0, but occasionally reaching over 9.0. In areas where the amount of organic material is higher, the plants will tend to grow to a larger size than those found in areas with lower amounts and the pH may be lower.
The plants can be found in full sun, but generally grow under some kind of shade. This may be provided by other plants, bushes, grass, etc, or larger rocks.
The following graph illustrates the correlation between annual rainfall and temperature. The blue line indicates the rainfall, with the scale on the left side of the graph and the line in red indicates temperature, with the scale on the right. The corresponding black lines are there to give a smoother line through the data. The months start in January and end in December, as if you couldn't guess !
The graph is composed of an average of data from 5 different localities in which Turbinicarpus species can be found. In each of these localities the amounts of rainfall and temperature will be slightly different to all of the other localities, but the general shape of the graph is always the same !
As you can see, there is a very strong correlation between these two factors. The year starts with relatively low rainfall and temperatures; there follows a rapid increase in the average temperature, which reaches its summer peak in May. In the meantime the average rainfall has remained fairly steady until April when there is also a rapid increase, which reaches its summer peak in June. When each of these factors reach there peaks, there are steady drops for a couple of months until July; at which time the temperature levels off until August and the rainfall increases to a new peak in September, that is generally higher than the peak rainfall in June. And now both the rainfall and temperature begin a rapid decrease for the winter.
Please note that the temperature values given on the graph are only averages and do not give the most accurate picture. In fact the ground temperature can vary from below 8 °C to 47 °C and above.
Like other cacti, species of Turbinicarpus have developed means of reducing water loss. They have a thick water proof cuticle that keeps water in and tries to keep pests and diseases out. Cacti have also recessed their stomata in deep pits over their bodies. (Stomata are pores in the epidermis of plants that allow the plants to "breath", they also allow water to escape when they are open.) By recessing these pores in pits, the amount of water that is lost is drastically reduced. Cacti, along with many other plant groups found in arid conditions, also only open these pores during the night, when the temperatures are much lower, thus reducing water loss even further.
But the most obvious adaptation to their environment is the development of large tap roots. The tap roots are used as water storage organs and send out longer, thinner lateral roots that absorb water from the soil. These root systems can provide over 80% of the total body mass of a plant, a fact that is very important to remember. During the periods of the year when water is available, the roots will absorb as much water as possible. Sometimes they will take in so much water, that the plants body will split open. During periods of drought the plants are able to use this stored water to survive. As this reserve is gradually used up the roots will slowly shrink and contract, pulling much, if not all, of the body under the surface of the soil.
The photograph on the right, of a plant from my collection, shows a typical tuberous rooted Turbinicarpus plant beginning to go into the winter dormant stage during October 1998. The body comprises perhaps 30-40% of the total body mass, the rest consists of the large tap root that ends in 3 or 4, thick lateral roots which subdivide into ever finer roots. It is these thread like roots that absorb the water and the fleshy tap root stores this water during the periods of drought. The long fleshy roots also have the function of anchoring the plant in the soil. This not only helps prevent the plant from being pulled out of the ground, but also means that as the main mass of the tap root starts to shrink, the body of the plant will be gradually pulled down, into the soil. Which keeps the plant away from the heat of the sun during the hottest periods and also reduces the chance of being eaten by an animal looking for a source of water.
In species formerly found in the genus Rapicactus, the root system is different to other Turbinicarpus species. Rapicactus consisted of plants like T. mandragora, and its subspecies subterraneus and zaragozae. In these species the body is separated from the tap root by a very thin, woody section. (Apparently, if the body of the plants dies, from drying out or being eaten, then the underground part will be able to generate a new body. Can anybody confirm or deny this ?)
In species of Turbinicarpus that have the thick, flexible, inward curving spines e.g. T. schmiedickeanus and its related taxa klinkerianus, gracilis and the relatives of T. macrochele etc., it has been shown that these species are able to absorb water with their spines. They can do this because the spines are filled with tube cells that run the length of the spine, which enable the absorption of water by capillary action. As can be seen in the photo on the left, these types of spines always have some degree of transverse cracking at fairly regular intervals. These cracks will obviously increase the amount of water that can be absorbed by the spines. This adaptation is probably primarily a method of absorbing water drops that form on the spines when a dew or fog forms.
In the species with this characteristic spine type, these spines are generally not persistent in habitat. This may be because they are knocked off by small stones or animals, or they may just fall off during the periods of shrinking and expansion caused by changes in water capacity. This means that this water collecting strategy is not as efficient as it could be. It is also interesting to wonder how the plants prevent water loss back through the spines !
Another possible adaptation is with regard to seed dispersal. Most species of cacti, in fact most seed producing plants, try to disperse their seeds as far as possible from the parent plant and many strategies have evolved for this purpose. In cacti this is usually done by enclosing the seeds in a brightly coloured, sweet tasting, juicy fruit, which animals such as insects, birds and small mammals will take back to their nest or eat. The seeds are covered in a protective coat so that they are not digested. When the animal defecates, hopefully some distance away from the parent plant, the seeds will germinate and they will have a supply of moist, organic matter to aid their growth.
However, in Turbinicarpus, together with some other cacti species growing with them, the seed is produced in a small, inconspicuous fruit and, in the case of most Turbinicarpus species, the fruit is hidden within the dense covering of wool produced on the top of the plant. In this way the seed is held on the body of the plant, possibly for a couple of years, until the seed finally falls onto the soil and germinates. This results in fairly compact groups of individual plants and because the parent plants grow well in this micro-habitat, hopefully the offspring will too.
Unfortunately there is also a down side to this strategy. Because the plant populations will tend to be confined to a small area, a side of a single hill for example, it is very likely that if any unscrupulous collector finds this habitat, they could quite easily remove every plant. I should add that not only are cactus collectors responsible for destroying these habitats, but there are also encroachments by humans, for habitations, road building etc. This has happened in the past, is happening now and, unfortunately, will probably happen for a long time to come.
The information given above, provides details of the conditions the plants receive in habitat. What we need to do is try to simulate, as best we can, these conditions in our greenhouses so that we can provide the best possible conditions for our plants. Unless you live in a climate that is the same as that encountered in habitat, at least some of the information must be adapted to fit in with the conditions that exist in captivity. As long as they are not left standing in water for any length of time, particularly during periods of low temperatures, Turbinicarpus species tend to be very resilient plants.
Please note that I live in England, where winter starts in about October and ends about March. They are wet and can reach temperatures as low as - 16°C. The summers are not as wet and temperatures can reach highs of 32°C. The information and advice given below are only guidelines and lessons that I have learned over the past 10 years, or so, of growing these plants. You may want, or need, to adapt them to suit your own particular situation. All I can say is that they work for me......most of the time.
The soil should be very well drained and contain nothing that will acidify it too much. I use a soil mixture of one part John Innes no. 2 soil, one part of sand (up to 2mm Ø) and one part coarse grit (up to 4mm Ø). I remove any lumps of fibrous matter from the John Innes before it is mixed with the other constituents. This is done because I believe that they will provide areas of soil that will retain water and may cause problems of rotting later on. The resulting medium is mixed thoroughly, making sure that any lumps of loam or peat are broken down.
For Turbinicarpus species that grow in areas where the soil consists of mainly gypsum, e.g. T. lophophoroides etc., they may be grown in soils that are composed of at least some part gypsum. Some people grow plants in neat gypsum, others add only a small percentage.
Pot choice is also a factor that must be taken into account, both clay and plastic pots can be used. The only significant (to the plants) difference, is that clay pots dry out quicker. The most important thing to take into account is the depth of the pot. We have already seen that species of Turbinicarpus can have massive tap roots and in fact one of the "secrets" of successfully cultivating plants with large tap roots, is remembering that most of the plant is underground. So we need to provide enough room for the root to grow, but not allow the root to be surrounded by too much soil. I tend to use BEF type square pots for most of my plants. For small (up to 2cm Ø) seedling plants I use 5cm Ø pots and pot them up to 7cm Ø deep pots when the roots reach the bottom. The most difficulty I have with these plants is with species such as T. valdezianus, dickisoniae and pseudomacrochele ssp. krainzianus fa. minimus, as all of these tend to have the usual long tap root, but they also tend to have a narrower diameter. So there will be comparatively more soil around the plants, for a given pot size, than for the more globose or offsetting species. This means that these species will, in my experience, need to be watered with more caution than the others. Another technique which can be used for these species is to place a couple of plants in the same pot.
There are also many species which have a shallow root system, this includes most species previously included in Gymnocactus and plants related to T. lophophoroides. For these species I use a dwarf pot which reduces the chance of the plant rotting
When potting plants I place some pieces of gravel (6mm Ø) in the bottom of the pots to prevent too much of the soil being washed away during watering. This is then covered with a layer of about 1cm of our soil mix and the plant held inside the pot at a level so that the "neck" of the plant is just below the rim of the pot. Soil is added and gently pressed around the plant, up to a level about 1cm below the "neck" and the pot is then top dressed with coarse grit, I use the same grit as in the soil mix. I then give the plant a light spraying with water, to remove any soil from the body.
I have found, here in England, all species that have reached a size of about 2.5cm Ø can stand as much sun and heat as they can get. Plants of this size and over are grown on a shelf in the eaves at one end of the greenhouse. Temperatures can reach as high as 50° C, so extra ventilation is provided during the hottest months. Growing them in this position means that the soil dries out very quickly, resulting in less of a chance of over absorption or standing in water logged soil. Growing them under these harsh conditions has the effect of making the plants grow quite slowly, resulting in tight compact plants and not the bloated blobs frequently encountered when species of Turbinicarpus are grown under easier conditions and also the spination is more robust. The only down side to this approach is that if any seed falls into the pots, the high temperatures tend to either prevent germination or kill any resulting seedlings. So if you want to grow them like this and propagate from your own seed, you must remove the seed as soon as the fruits ripen.
We learned above that in habitat Turbinicarpus species only receive significant amounts of water when the temperatures are warmer, so this is the factor that will govern whether we can give any water to the plants. Here in England this means that most of my plants only receive water between March and October. The exceptions being the early flowering species like T. schmiedickeanus, and related taxa such as andersonii, rubriflorus and T. valdezianus. These are given a small amount of water, from a spray, as soon as any flower buds are seen. But make sure there is some ventilation.
The most important thing to remember when watering the plants for the first time, after a period of dry winter dormancy, is that we must only give small amounts of water to begin with. If they are given a good soaking as soon as the warmer weather arrives, the roots will absorb as much water as possible, which may result in the plants bursting. You have been warned !
Once the warm weather has arrived and the plants have expanded to their normal size, you can give water as frequently as required. I generally water all of my plants, not only the Turbo's, about every one or two weeks during the warmest periods. During these warmer spells the Turbinicarpus pots will have dried out completely within two days. I have found that between the middle of July and the middle of August, the hottest period here in England, the plants tend to go dormant. During this period I only give half the amount of water I would normally give. This seems to correlate well with the drop in rainfall and temperatures in the graph shown above.
I tend not to feed Turbinicarpus species more than about twice each year. This is partly because they do not require that much feeding, but mainly because the other plants I grow are Notocactus, Gymnocalycium and Weingartia. These genera prefer a soil with an acid pH (below 7). I accomplish this by using a feed that gives a slightly acid solution and, as we have seen, Turbinicarpus species tend to prefer a slightly alkaline pH (above 7).
As soon as the colder weather starts to appear, here in England that is about October, I reduce watering to heavy spraying of the gravel topping and in November watering is stopped altogether, except as stated above for the early flowering species.
In my experience of growing Turbinicarpus and other choice species of cacti under the conditions detailed above, I can honestly say that I have never had any trouble from any type of pest. The relatively high temperatures tend to cook any pest stupid enough to try to feed on my plants. (Just pause for a moment and think of that big fat juicy mealy bug, frying in its own juices ! Doesn't it just make you feel so happy and warm inside ? But not as warm as the mealy bug, ha ha hahaha !!!)
However, as soon as the first warmer days of February appear, I give all of my plants a spray with a contact insecticide. Just to reduce the chances of any unwanted visitors over wintering in the greenhouse.
The only disease generally encountered in Turbinicarpus is rotting, caused by too much water or watering when it is too cold. Unfortunately, due to the fact that most of the plant is underground, it is difficult to catch rotting before the plant is past helping. If you do catch the rot, during potting is usually the time, remove all traces of the damaged tissue and keep removing the tissue until no traces of the brown infected areas are left. Cover the cut area with some form of fungicidal powder, in the past I have used Benlate powder or hormone rooting powder. The later contains fungicide as well as the rooting hormone. The plant should be left in a warm, shaded position until the damaged area has callused, generally this takes about two weeks. Once the damaged area has healed you can place the plant in a pot of the slightly moist, sterile medium of your choice, sand, vermiculite, normal soil mix etc., and leave in a warm, light position. Providing bottom heat will encourage regrowth. Hopefully in a couple of weeks there should be signs of regrowth.
There is also the special case of what to do if the plant splits, due to over watering. I have only ever had one Turbinicarpus species split and I successfully managed to save the plant and keep it alive for a number of years. The thing to remember is that if the split is very large, mine was about 2cm, then in all probability the plant will eventually succumb. This may be from the scared tissue being a weak point and allowing further splitting in later years or allowing attack by fungi.
I first noticed that a T. macrochele had split in early march, after being over zealous with the water. I immediately removed the plant from its pot, which stops any more water from being absorbed by the roots and therefore reducing any further splitting. I completely filled the split with Benlate powder. This is a fungicidal preparation that contains Benomyl. I assume any fungicide will work, the main purpose for using the powder to fill the split is to try to remove some of the liquid from the plant and therefore reducing the chance of any further splitting. Believe me it works ! The plant was left like this until early summer, about the beginning of May, and fortunately no more damage had occurred, in fact the split had almost closed. The plant was then planted back in its old pot, but it was only submerged up to just below the level of the split with soil. The rest of the pot was filled with topping grit. This plant lasted another 3 years before it gave in and died, but during that time I was able to propagate it from its seed.
If this happens to you, just remember that it's probably going to die sooner or later. So make sure you take special care of it and try to propagate from it, either from seed or by removing any offsets which may be produced as a consequence of the damage caused.
Another problem I have encountered is in relation with the fact that some species can absorb moisture through their spines. Here in England the winters can be very damp. If these species absorb this moisture with their spines, there is a chance that a black mould will form on the surface of the spines, causing an unsightly discoloration. So what I do once or twice over the winter is to give these species a light spray with a fungicide, just enough to wet the spines. This seems to have prevented any further attacks over the past couple of years.
Propagation of Turbinicarpus species is easily carried out by means of seed. Seed can be sown in small 5cm Ø pots two thirds filled with a sterile 50:50 mixture of John Innes seedling compost : sharp sand. The seed is evenly distributed around the surface of the pot. The pot is given a good watering with a solution of fungicide and then placed inside a sealed plastic bag and placed on a window sill. Temperatures should be kept below about 30°C. Germination should be fairly fast, certainly within 3 weeks. The growing seedlings should be watered occasionally, to keep the soil slightly moist, and any dead seedlings should be removed. When the seedlings are about 1cm high or start to force each other out of the soil, they should be potted up into individual 5cm Ø pots containing the usual potting mix. The growing seedlings should be kept out of the full sun until the typical thick epidermis has appeared. Then treat as adult plants, but just make sure they do not scorch in the hottest sun.