Root-Rot on calathea
What's Happening
Calathea's fine, fibrous root system lacks aerenchyma tissue (oxygen-transport channels) found in wetland plants, making it extremely vulnerable to anaerobic conditions. When soil remains saturated 5+ days without drying, oxygen levels drop below 2mg/L threshold. Beneficial aerobic bacteria die; anaerobic pathogens (Pythium, Fusarium, Erwinia) proliferate, producing toxins that destroy root cortex tissue. The infection spreads from root tips upward, turning roots black/mushy with characteristic foul odor. Unlike succulents that store water, Calathea's high transpiration rate from large leaves means root failure causes rapid collapse—often within 48-72 hours of critical root loss.
How to Fix It
- 1
Unpot immediately and gently rinse ALL soil from roots under lukewarm water
- 2
Trim ALL black, mushy, or foul-smelling roots with sterile scissors until only firm white tissue remains
- 3
Soak remaining roots in 3% hydrogen peroxide (1:1 with distilled water) for 20 minutes to oxygenate and sterilize
- 4
Dust cut ends with cinnamon powder (natural fungicide) or dip in rooting hormone with fungicide
- 5
Allow roots to air-dry on paper towel 24-48 hours in shade to callus wounds
- 6
Repot in fresh, sterile aroid mix (50% orchid bark, 30% perlite, 20% coco coir) in pot with drainage holes
- 7
Wait 5-7 days before first light watering; maintain 70-80% humidity to support recovery
What You'll Need
How to Prevent It
Water only when top 1-2 inches are dry—finger test or moisture meter. Use chunky, well-draining aroid mix with 40%+ inorganic material (perlite, bark). Always use pots with multiple drainage holes. Switch to terracotta for natural moisture wicking. Never let pot sit in standing water. Aerate soil monthly with chopstick to prevent anaerobic pockets. Bottom-water only when necessary to control saturation.