Introduction Conophytums grow in the western part of South Africa and also in south-west Namibia. This area has rain falling in the winter and with dry summers. Therefore plants in the wild are winter-growing and conos persist in this behaviour in cultivation.
Watering Conophytums have a summer “resting” period, during which time the existing leaves dry up and protect the next-season's leaves in a papery sheath. Watering is resumed about the end of July and is quite heavy for about two months, perhaps once a week depending on weather. During this period the new leaves develop rapidly, splitting the old sheath, and in most species the flowers are then produced. As it gets colder and the day length decreases in the autumn, watering is reduced to a level of about once every three or four weeks through the winter. Certain species, e.g. Conophytum calculus, start to produce obvious wrinkles when they need a drink and I use these as marker plants to determine when the collection needs water. Around about mid February, the conditions start to improve and frequency of watering is increased once more; it is during this period that the new leaves are starting to form inside the existing ones. Watering is stopped in early April and the plants enter their dry phase. I do not water my conos at all during the summer, but some successful growers do continue with very light watering, particularly of the smaller-headed species. Please note that any spraying or overhead watering during this period can result in tannins being leached from the sheath, discolouring the new heads below. I like my conos to grow as hard and compact as possible, therefore little feeding is required. I use low-nitrogen liquid feeds, once during early spring to help the new leaves form and also once in the autumn if plants have not been repotted.
Light The beauty of many conos is in their body coloration and high light levels are needed during the growing season to maintain this. Therefore during the winter, plants should be placed in the brightest possible position in the greenhouse. About the beginning of May, we often experience our first very hot and sunny days of the summer and there is a big danger of conos scorching at this time. In fact this is probably the biggest problem in growing the genus. The effect of the sun is often not seen until plants start growing in the autumn, when south-facing heads on the clumps are seen to be dead. In an attempt to avoid this problem, I paint white shading on the glass over the conos in April; removing it again in September. Alternatively if you have a small collection, move the plants to a shadier part of the greenhouse for the summer.
Temperature In general I would recommend a greenhouse with frost-free conditions. In the wild, some of the conos that grow at higher altitudes do experience frost and snow. It should be possible to select some conos to grow under unheated glass (a friend grew a Kamiesberg form of C. pellucidum in an alpine house for some years). My greenhouse does not go below 3oC during the winter. Good ventilation is important, especially in summer and try to avoid temperatures over 40oC.
Potting I always use plastic pots for conophytums; clay pots in small sizes dry out far too quickly. In sizes of 9cm and over, use pans rather than the deeper pots because most conos are shallow-rooting. Very small plants are best grown several to a pot to avoid too much unused compost. A standard growing mixture is equal parts of soil based compost and small quartzite grit, but any free-draining loam-based soil mix is suitable. Conos are very adaptable and it’s worth experimenting with soil mixes to find one which suits your particular conditions. Ideally plants should be repotted about once every two years, but I have many plants that have been untouched for much longer. The best time to repot is early in the growing season, July-August, but it can be done at almost any time while the plants are in growth. There actually seems to be more new root formation during the winter than in the autumn. Clean as much of the old compost from the roots as possible using a pointed label or stick and a small brush.
Pests The genus is relatively trouble free but root mealy-bug can sometimes occur. Watering with a suitable insecticide (imidacloprid is particularly good as the active ingredient) once during the autumn is suggested as a prophylactic measure. Western flower thrips are often seen on cono flowers, but they do not seem to do any damage. Spraying with a contact insecticide during the growing season will provide some control. Sometimes snails and tortrix moth caterpillars start munching the plants and both are best hunted at night. General hygiene and appearance of conophytums is improved by carefully removing old sheathes after the new leaves have broken through. Removal of dead flowers avoids them becoming a source for botrytis.
Cuttings Old plants tend to loose vigour and are best broken up into cuttings. You can also propagate desirable plants by removing growths (bodies/heads) from around the edges of a clump, but I often find it easier to knock the plant out of its pot to do this. In both cases, cuttings should be taken after the leaves have developed properly in the autumn and September and October are the favoured months, when the plants are most vigorous. I have even taken cuttings successfully as late as February, but artificial bottom heat is usually necessary to root cuttings during the winter. A cutting should consist of just one or two growths with no more than a couple of millimetres of stem below the soft tissue. Put them in the greenhouse with your other conos and keep the soil moist. Rooting should take place within weeks in autumn but one or two months later in the season.
My thanks to Dr Terry Smale for permission to use this growing guide.