Root Rot on calathea
What's Happening
Calathea root rot develops when rhizomatous root systems remain in waterlogged, oxygen-depleted soil for 5-7 days. Unlike fibrous-rooted plants, Calatheas store energy in thickened rhizomes at the crown (base of stems). When soil saturation exceeds root oxygen demand, anaerobic bacteria (Erwinia chrysanthemi, Pythium species) proliferate, consuming root tissue and releasing toxins. Early stages show yellowing lower leaves and slowed growth; advanced stages exhibit mushy stems, foul odor, and plant collapse. The thin, delicate root hairs—critical for nutrient absorption—die first in saturated conditions, triggering a cascade of decline even before visible symptoms appear.
How to Fix It
- 1
Immediate unpotting: Gently remove plant from pot; shake off all soil to expose root system
- 2
Root triage: Trim ALL black, mushy, or foul-smelling roots with sterile scissors until only firm, white/cream tissue remains
- 3
Crown inspection: Check rhizome at leaf bases—firm potato-like texture is healthy; soft/mushy indicates crown rot (may be unrecoverable)
- 4
Sterilization: Soak remaining healthy roots in 3% hydrogen peroxide solution (1:1 with water) for 20 minutes to kill bacteria
- 5
Callus period: Lay plant on dry paper towel in shade for 48 hours to seal cut surfaces and prevent reinfection
- 6
Repot in fresh sterile mix: Use 50% peat, 30% perlite, 20% orchid bark; ensure pot has drainage holes; use plastic pot (not terracotta)
- 7
Recovery watering: Wait 1 week after repotting before first watering; then resume when top 1 inch dries
How to Prevent It
Use pots with drainage holes exclusively; water only when top 1-2 inches of soil are dry; never let pot sit in standing water; avoid terracotta which wicks moisture too aggressively; ensure bright indirect light to drive transpiration; use well-draining soil mix with 40%+ perlite/bark.