Botanical Name — Tephrocactus geometricus
Plant Family — Cactaceae
Tephrocactus geometricus is native to the Argentina Catamarca and Bolivia border. They grow in an extreme desert habitat, between violet and red rock in flat or moderately steep sandy soils. Tephrocactus geometricus are small low growing globular segmented cactus that grow branched into small clumps. The stems are blueish green that reddens to purple in full sun exposure. New growth is dark purple. Spines are black.
- These cacti prefer lots of sun, at least 5 to 8 hours of direct sun daily.
- Indoors a south facing window is ideal. Outdoors seat them in a place where they will get plenty of sun exposure, but protect them from intense, peak afternoon sun.
- Tephrocactus geometricus likes it hot! Above 70 ºF in the summer is preferred.
- During the winter they prefer cooler temperatures between 50 to 60 F. The cooler temperature will encourage flowers. They can tolerate light frost down to 25 F.
- 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.
- These plants prefer a sandy, sharply draining mix. Cacti or succulent potting mix is great. You can amend a regular potting soil with sand or pumice up to 50% to improve grittiness and drainage.
- Large flowers that are white to light pink with a darker midstrip. Flowers last only one day.
- These plants 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.
- Propagation by seed or cuttings.
- Since seeds are extremely difficult to germinate, cuttings are an easier way to propagate.
- Cutting can be taken at the base of the segment of a plant. Let callus a couple of weeks and plant in dry soil and keep dry till rooted. Since these plants are slow growers and you can graft the cutting to speed up the growth rate.
- Tephrocactus geometricus are not prone to pests. Though not super common, they are more likely to fall victim to bacterial or fungal infections. Affected plants may need to be destroyed to prevent the spread of disease to other nearby plants.
- Root rot can also be a concern and is triggered by overwatering. Always err on the side of underwatering.
Maintenance (pruning, legginess, repotting)
- Little maintenance is required to grow these plants. They do not require frequent repotting unless they are out growing the planter. Repot once every two to three years to refresh the soil.
- They are prone to fall apart because they have very weak segmental attachments. Plants need to be handled with extreme care to keep them all together when repotting.
- Tephrocactus geometricus are not known to be toxic to humans or pets but should not be ingested.