Star Rock Cactus (Ariocarpus trigonus)

Star Rock Cactus

Ariocarpus trigonus

Its star-shaped rosette holds desert quiet, a slow-growing living sculpture. Succulent cactus; common names: Star Rock, Living Rock Cactus.

Full sun
0.5/week
Moderate
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Plant Needs

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Sunlight Full sun to bright indirect light; provide partial shade during intense midday summer heat to prevent sunscald
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Watering Allow soil to fully dry between waterings; avoid overwatering to prevent root rot, especially during dormancy
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Temperature Thrives in warm, dry conditions; tolerate brief light frost down to 5°C but avoid prolonged cold or freezing temperatures
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Characteristics

  • Leaf: Modified into small, triangular tubercles arranged in star-shaped rosettes; no visible spines.
  • Flower: Pale pink to white, funnel-shaped, 3–5 cm diameter, blooms from the rosette center.
  • Stem: Compact fleshy rosette with a large underground taproot for water storage.
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Care Guide

Watering

Water thoroughly when soil is completely dry; reduce frequency during extreme heatwaves

Fertilization

Diluted cactus fertilizer once monthly. Do not fertilize during dormancy; use a low-nitrogen, high-phosphorus fertilizer to support flowering

Eggshell powder topdressing:Grind dried eggshells into fine powder; sprinkle lightly on soil surface; avoid direct contact with tubercles to prevent irritation
Pruning
  • Remove dead, shriveled tubercles to maintain a tidy rosette shape
  • Trim damaged or rotting taproots only during spring repotting
  • Avoid excessive handling to prevent scarring of the fleshy tubercles
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Non-toxic to cats; no adverse effects from ingestion or contact

Humans: No known toxicity to humans; safe for handling and proximity

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Garden Uses & Culture

Culture: N/A

Usage: Ornamental succulent for rock gardens, container collections, or xeriscaping