Tephrocactus geometricus (Black Spine Form)
Tephrocactus geometricus is a distinctive species from northwest Argentina, known for its sculptural shape and chalky blue-grey color. The stems grow as rounded segments - almost perfectly spherical on some plants - with a matte surface that looks a bit like stone. These segments stack and branch slowly, eventually forming low clusters.
This is one of the more sought-after members of the Tephrocactus genus, and it’s easy to see why. In cultivation, it prefers excellent drainage and plenty of light, but it’s more cold-tolerant than many globular cacti and can handle light frosts when dry. Water sparingly in winter.
Tephrocactus geometricus is slow growing and doesn’t offset rapidly, which makes larger specimens especially prized. Avoid repotting too often - the segments detach easily, but re-rooting can be slow. Best suited to collectors who appreciate patience and clean architecture.
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