Alocasia macrorrhizos

Natural range and habitat of Alocasia macrorrhizos

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.

Growing Alocasia macrorrhizos

Stem support: Keep the pot stable as the plant gains size. Add support only if a stem actually becomes unstable.

Space: Plan for a massive plant with a thickening stem. Give it substantial floor and overhead room and use a pot heavy enough to balance it.

Watering: During active growth, check moisture well below the surface and water while some moisture still remains deeper around the roots, before that part of the pot becomes dry. When growth slows and the pot dries more slowly, extend the interval between waterings. Soak the root ball evenly and let surplus water escape before the plant goes back into its outer pot.

Potting mix: Use a fertile mix that holds moisture and has enough chunky material to stay airy and let excess water drain freely.

Light: Give it abundant filtered light indoors and introduce stronger sun gradually.

Temperature: Alocasia macrorrhizos grows steadily at about 18–30 °C. Move it away from the coolest part of the room before temperatures stay under 15 °C.

Humidity: Maintain the growing area close to 60–80% humidity around the foliage. Provide enough light circulation to keep the air from becoming still. A bright, sheltered indoor position suits it, away from heater and air-conditioning airflow.

Feeding: Feed with a complete houseplant fertiliser while new leaves are growing, at modest strength. Increase the feeding frequency modestly while new growth is strong. Leave out fertiliser during periods of slow growth.

Repotting: Give the roots more room as they fill the pot, moving up gradually in container size.

Propagation: Separate a rooted basal offset, preserving as much of its established root system as possible. Pot the offset separately and keep conditions warm while its roots settle.

Alocasia macrorrhizos: common problems

• Lower leaves turn yellow and droop while the pot remains heavy: Hold off on the next watering and examine the roots and base. Mushy, collapsing or foul-smelling tissue points to rot. Keep all firm tissue, remove only clearly rotten parts and replace damaged potting mix with a fresh, airy one.
• New leaf stalks grow longer and the plant starts leaning towards its main light source: Move it to a brighter position with indirect light reaching more of the plant. Turn the pot gradually over time so future growth is better balanced. Existing stretched stalks will not shorten.
• Brown leaf margins keep returning: Look at how evenly the root ball has been drying, then check for hot, dry air and a build-up from feeding or hard water. Fix the most likely cause and use the next leaves to see whether the problem stops.
• New growth emerges misshapen with surface scarring or pepper-like dark dots: Before the leaf unfurls fully, check the inner folds and nearby new growth for thrips or fresh droppings. If you find clear signs, isolate the plant before treatment. Use a treatment labelled for thrips on indoor ornamental plants, and repeat it only as directed on the label.

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.