⚠ CriticalAlocasia Corm Rot — Overwatering During Dormancy
Commonly affects: Alocasia spp., Alocasia amazonica, Alocasia odora
The underground corm (bulb-like storage organ at the base of the plant) becomes soft, mushy, and discoloured — ranging from light brown to near-black. In healthy Alocasia, the corm is firm, pale beige, and dry. Rotted corms have a distinctly sour or fermented smell. When the corm rots, the plant loses its anchor and energy storage, typically causing sudden total collapse of all stems and leaves.
Potential Causes
- 1Continued regular watering during dormancy, when the plant's metabolic rate is too low to consume soil moisture before rot pathogens colonise
- 2Cold, wet substrate creating anaerobic conditions that favour Pythium and Fusarium — Alocasia corms are particularly vulnerable below 15°C
- 3Corm damage from physical handling during repotting creating entry points for fungal infection
- 4Planting the corm too deep or burying it in dense, water-retentive substrate without adequate drainage
Solution Steps
- 1Unpot the plant immediately and remove all substrate from around the corm. Inspect under good lighting — soft, discoloured sections indicate active rot.
- 2Use a clean, sharp knife or scalpel to cut away all rotted corm tissue, working back to firm, pale flesh. Sterilise the blade with alcohol between cuts.
- 3Dust all cut surfaces with powdered sulfur or activated charcoal and allow the corm to air-dry in a warm, bright location for 24–48 hours to form a callus.
- 4Treat the remaining healthy corm with a dilute fungicide solution (thiophanate-methyl) for 15 minutes as a soak before replanting.
- 5Repot in a very well-draining mix (equal parts perlite, orchid bark, and a small amount of potting soil) in a pot only marginally larger than the corm.
- 6Do not water for 7–10 days after repotting — allow the callused tissue to stabilise before exposing the root zone to moisture again.
Prevention Tip
When Alocasia enters dormancy (typically in autumn/winter, signalled by leaves yellowing and dying back), reduce watering to once every 2–3 weeks — just enough to prevent the corm from desiccating completely. Never water on a fixed schedule during dormancy.
Related Issues to Explore
Root Rot — Pythium & Phytophthora Infection
Pythium and Phytophthora are the primary agents of corm rot — the same fungicidal and substrate protocols that treat root rot apply to corm recovery.
Read guide
Winter Dormancy Stall — Alocasia's Seasonal Growth Pause
Understanding the dormancy cycle that triggers reduced growth is essential for correct corm care — watering during dormancy as during active growth is the primary cause of corm rot.
Read guide
