Alocasia macrorrhizos

Where Alocasia macrorrhizos grows naturally

The natural range of Alocasia macrorrhizos extends from the central Malay Archipelago through New Guinea and the western Pacific to northern Queensland. It grows vigorously in warm, rainy tropical regions, often in moist lowland ground where gaps in the canopy provide filtered light.

How to care for Alocasia macrorrhizos

• Light: Give it abundant filtered light or gentle morning and late-afternoon sun after acclimation. Strong midday sun can scorch the broad leaves.
• Humidity: Maintain relative humidity around 60–75% where practical.
• Watering: During active growth, water when the upper few centimetres have partly dried and the deeper root ball remains lightly moist. Check below the surface because large pots can stay wet in the centre.
• Airflow: Provide gentle air movement around the large leaves and protect them from strong draughts and heated air.
• Temperature: Keep it at about 20–30°C, with a warm root zone during active growth.
• Substrate: Use a rich, open mix of coco fibre or peat, medium bark and pumice or perlite. A large plant needs useful water retention and fast drainage.
• Feeding: Feed regularly with a complete fertiliser at low to moderate strength during active growth. Reduce feeding as growth slows and flush the pot periodically.
• Support: Add discreet support if a tall plant becomes unstable, leaving free space for each new leaf to open.
• Repotting: Use a heavy, stable container with generous drainage, increasing its size gradually as roots fill it. Keep the thick stem at its existing depth and repot during warm active growth.
• Propagation: Basal shoots or rooted corms can be separated once they have enough roots to establish independently.
• Handling safety: Before repotting or unpotting, disturbing the root ball, cutting, pruning, division or propagation, wear gloves and keep Alocasia sap away from skin and eyes. After handling, wash hands and clean tools.

When Alocasia macrorrhizos needs attention

• One lower leaf turns yellow while the crown stays firm: A single oldest leaf can yellow during normal turnover and needs no action while healthy new growth continues.
• Several leaves yellow, the plant wilts in wet substrate or the base softens: Check root-ball moisture. Water thoroughly and drain when genuinely dry and firm at the base; if wet, stop watering and empty standing water. If decline persists, wear gloves and keep sap away from skin and eyes before unpotting or cutting. Retain all firm roots and remove only directly confirmed brown or black roots that are mushy, hollow or slimy, or outer tissue that slips away. If roots are firm, do not cut them. Repot surviving roots in fresh airy medium in a clean draining pot sized to them, then wash hands and clean tools. Seek professional diagnosis before cutting if the lower stem, base or crown is soft or the boundary is unclear.
• A broad leaf tears after handling: Give foliage room and prevent repeat contact. Leave a clean, dry injury in place while it remains firm and stops changing.
• A tear becomes water-soaked or brown spots multiply: Isolate the plant, keep foliage dry, stop splashes and mark lesion edges. If a small number of severely affected leaves must be removed, wear gloves and keep sap away from skin and eyes before cutting with disinfected tools; discard them, disinfect tools again, then wash hands and clean tools. Continued spread, recurrence, movement into a petiole, crown or base, soft stem tissue or several affected plants needs professional diagnosis before further cutting or chemical treatment.

Alocasia macrorrhizos: toxic if chewed

• Pets: This Alocasia is toxic to cats and dogs. Keep the plant and any cut pieces where pets cannot chew them.
• Children and handling: Keep it out of reach of children. Sap from damaged tissue can irritate skin and eyes, so wash your hands after pruning and avoid touching your face.
• Why it irritates: Alocasia tissue contains insoluble calcium oxalate crystals. Chewing or contact with sensitive tissue can cause immediate local irritation.
• Possible symptoms: Mouth exposure can cause burning pain, drooling, swelling, nausea or vomiting, and difficulty swallowing.
• After exposure: For a pet, contact a veterinarian. For a person, remove any plant material from the mouth and rinse with water; seek medical or poison-control advice if symptoms are significant. Breathing difficulty or rapidly increasing swelling needs urgent medical attention.

What macrorrhizos means

Macrorrhizos combines Greek makros, “large” or “long”, with rhiza, “root”, giving the meaning “large-rooted”.

Carl Linnaeus named the species Arum macrorrhizon in 1753 in Species Plantarum, page 965. George Don later published the combination Alocasia macrorrhizos in 1839 in Hortus Britannicus, third edition, page 631.