South America is the home of the large genus Gym-nocalycium, which includes more than 80 species. Many are often found in cultivation and some, or rather their colour forms, have even become ‘fashionable’ plants. Mention has already been made of G. mihanovichii, which comes in red, orange, pink and yellow. This is caused by lack of chlorophyll and the plants would not be able to survive under normal conditions, for they are incapable of carrying out photosynthesis. That is why they must be grafted in the seedling stage on to stock which provides them with food. These colour aberrations have become very popular, chiefly in Japan, where they are raised and multiplied by special nurseries.
The species is a flattened spherical shape, about 7 cm (2-3/4 in) across, later becoming cylindrical and attaining a height of 15 cm (6 in). There are usually 11 ribs broken into tubercles separated by sharp cross grooves. Each areole produces 5 radial spines about 0.5 cm (1/4 in) long. The skin is grey green, appearing reddish in the sun. Theare relatively large, about 6 cm (6-1/2 in) long, white with a red centre.
Gymnocalycium quehlianum is native to the mountains of Cordoba in central Argentina. Because it grows at high altitudes it does not tolerate excessive sunlight and heat combined with a dry atmosphere, which other cacti find congenial. In its native habitat it grows in grassy places and thus it is best to provide it with light shade in summer. Watering, which generally alkalizes the, causes the plant to lose its roots for they are intolerant of an alkaline environment. It is therefore recommended that gymnocalycium be grown in fine crushed brick, the re-quired nutrients being supplied by being added to the water. Cultivation will thus pose no problems and the plant need not be moved for years.