Origin and Habitat: Unknown.

• Aztekium ritterii f. senilis hort.

• Aztekium ritteri Boed.
• Echinocactus ritteri Boed.
• Aztekium ritterii f. cristatum hort.
• Aztekium ritterii f. montruosa hort.
• Aztekium ritterii f. senilis hort.

Description: Aztekium ritteriSN|4248]]SN|4248]]i f. senilis is a nomen nudun (an avowed new name unaccompanied by a description or diagnosis) sometime used in the trade to indicate a woollier form of Aztekium ritteriSN|4248]]SN|4248]]i distinguished by its areoles densely covered by tufts of soft tangled greyish-white hair. The true self and the origin of this plant is controversial, some suppose that it may be a mutation or a new variety. However the density of wool in the areoles is greatly influenced by the conditions of culture: plant on their own roots usually have few felty hairs only on the upper areoles, while in grafted specimens the hairs are more numerous. In any case the "senilis form" is very peculiar and seldom seen in specialized collections.

Cultivation and Propagation: Aztekium are by far the most challenging and difficult cactus to grow, they are of extremely slow growth - probably the slowest of the entire cactus family. They usually take several years for growth to be even noticeable. Once a specimen is established on its own roots it is no trouble to keep it ,and becomes an easy plant to manage.
Water requirements: They need good drainage and regular water in summer. They should be dried out completely for their winter rest when they will withstand temperatures down to to -4°C for short periods.
Light requirements: They prefer some shade.
Propagation: It usually multiplies by seeds. The seeds are extremely fine and germinate readily, but the seed germination rate is very low for everyone (less than 5%). The minute seedlings are very sensitive for the first two months. But many of them perish, and taking them to a viable size is very difficult. The seedling are so small that a drop of water moves them like crazy. They are usually grafted to increase growth speed. In any case, grafting produces rather atypical plants which tend to be more obese and to offset much more readily than plants growing on their own roots. The offsets of grafted plants are often produced from areoles high up on the plant body, rather than at ground level. It is also possible to root the offsets from grafted plants, but with little success.