A rare and unique cactus, the Tephrocactus geometricus are small low growing globular segmented cactus that grow branched into small clumps. The stems are blueish green that will redden to purple in full sun exposure. New growth is dark purple. Spines are black. This is a very slow growing cactus, only one globe per year may grow.
In the summer months, water only when the soil has dried out completely. Always err on the side of underwatering. They are built to withstand drought, and overwatering is one of the quickest ways to kill them. Water less in the winter months and only when there is a stretch of sunshine in the forecast.
These cacti prefer lots of sun, at least 5 to 8 hours of direct sun daily. Indoors a south facing window is ideal. Outdoors place them where they will receive plenty of sun exposure, but protect them from intense, peak afternoon sun.
The Tephrocactus do not require fertilizer though it can be added to give container grown plants a boost or to supplement poor soil. Apply a water-soluble, balanced fertilizer monthly, diluted at half strength.
The soil must have good drainage, and it must be porous. Combine cactus mix with sand, pearlite, or another mineral that helps with the porosity. In case you could not find the cactus mix, you may opt for using potting mix. Keep in mind that the mineral must be present in a greater quantity than the cactus mix, for example, 25% cactus mix, and 75% mineral.
this plant can go in hot temperatures as well as frosting times. Just be sure it is not receiving water, and everything will be right.