Tephrocactus geometricus

Botanical identity and natural origin of Tephrocactus geometricus

Tephrocactus geometricus is native to Catamarca in north-western Argentina, where it grows in desert and dry-shrubland habitat.

Tephrocactus geometricus is accepted as a species and has also been treated as Tephrocactus alexanderi subsp. geometricus.

Care for Tephrocactus geometricus

• Shape and light: Very bright light and direct sun help new joints retain their compact rounded form. Increase exposure gradually after a lower-light period.
• Temperature: For active indoor growth, aim for 10–26 °C. Give it warm conditions while actively growing. For a cool resting period, keep it at about 6–14 °C. Keep the plant frost-free.
• Humidity and airflow: Average room humidity around 40–50% is sufficient; keep the plant well ventilated.
• Water: During active growth, water once the mineral-rich cactus mix has dried completely. During the cool resting period, keep the mix dry.
• Feeding and repotting: Use a light feed while the plant is actively growing. If the mix stops draining quickly, replace it with fresh mineral-rich cactus mix. When roots occupy the available space, shift the plant into a pot only a little larger.
• Handling and stability: The stacked joints can loosen after knocks. Use a stable pot and handle the clump from below when moving it.
• Propagation: Detached healthy joints can root after the wound has dried and formed a callus; the species can also be raised from seed.

Common problems with Tephrocactus geometricus

• New joints stretch and lose their rounded shape: Increase light gradually.
• Segments wrinkle after the mix has stayed dry for a long time: The plant may need water, or the roots may be damaged. Check the roots before changing the watering frequency.
• A joint turns yellow-brown, translucent or soft: Rot is developing. Remove the affected segment, cut away rotten tissue back to firm healthy material with a clean tool, discard all rot and let clean wounds dry before re-rooting.
• Waxy white insects or small fixed brown bumps appear between joints: Mealybugs or scale may be present. Isolate the cactus and use a product labelled for the identified pest and indoor ornamental plants, following the label interval.

Tephrocactus geometricus has sharp parts

• Keep this plant away from children and pets because its effects after chewing or swallowing are unclear.
• Fine glochids and larger spines can lodge in skin, paws, mouths or eyes and cause painful irritation.
• Handle it carefully. Contact a veterinarian or medical professional after a serious injury, especially to the eye.

When was Tephrocactus geometricus first published, and what does it mean?

Tephrocactus means ash-grey cactus. The epithet geometricus means geometric.

Charles Lemaire established the genus Tephrocactus in 1868 in Cactées, page 88.

Alberto Castellanos first described it as Opuntia geometrica in 1934 in Kakteenkunde, volume 1934, page 172. Curt Backeberg later placed it in Tephrocactus as Tephrocactus geometricus in 1936 in Kaktus-ABC, page 111.