About the genus
Turbinicarpus is a genus of choice, slow-growing cacti, which has had many names changes and has included Rapicactus, Gymnocactus, Normanbokea and Kadenicarpus. They are all from Mexico and are very slow growing but can flower when the plant is only 2cm in diameter.
The first Turbinicarpus was described by Bödecker in 1927 as Echinocactus schmiedickianus. Backeberg included it as a subgenus named Turbinicarpus in the genus Strombocactus. It was raised to the rank of genus in 1937, and the first species described was T. klinkerianus by Backeberg and Jacobsen in 1948.
They are mostly found on limestone soils, with some in almost pure gypsum, and many species grow on sloping sites in cracks and niches. Their taproot acts as an anchor in the loose stony soil, but more importantly serves as a water storage organ for periods of drought. The species are often depressed in the soil or level with the ground and may prove difficult to spot until they flower.
How to grow them
Turbinicarpus requires full sun in order to maintain good body colour and spine development. Winter temperatures can be set at 6°C, but providing the plants are kept dry and humidity levels are kept low by good ventilation on bright days, the plants can happily withstand colder temperatures for brief periods. During hot midsummer periods, the plants may go into dormancy, so reduce watering then. The plants should remain completely dry for the winter months.
The golden rule when watering Turbinicarpus is to never water when the substrate is still wet. Watering should commence in the spring, depending on weather conditions, and the plants should initially be given a light spray. Several species with papery spines, such as T. schmiedickeanus, can absorb water through their spines. Never introduce water too quickly as the plants may take up too much and split. Once the plants have swelled up after their winter rest, the water can be increased. Water thoroughly each time, and this should be about every two weeks. Water sufficiently to ensure it runs from the bottom of the pot but try not to water over the top of the plant, especially if it is a hot sunny day, as this can scorch it. Always choose a bright sunny day to water and do it early morning to allow excess moisture to dry up.
It is important not to over fertilise. Overfeeding and overwatering will produce bloated unnatural-looking plants. These are miniature plants and really one liquid feed per year using a general cactus fertiliser applied during the spring is probably all that is needed.
Regarding propagation, as most species are solitary, they do not produce offsets. Fortunately, most species are easily propagated from seed, and success levels are good. Seedlings tend to grow away quite quickly and can produce flowering-sized plants within just a few years.
Turbinicarpus do not seem to be very susceptible to pests. The one problem that all species can succumb to is rot, easily killing any plant within just a few days, therefore a well-drained substrate with high non-organic content is essential.
Photos: Philip Andrews
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