Root Rot on begonia
What's Happening
Begonia roots succumb to anaerobic bacterial and fungal pathogens (Pythium, Fusarium, Erwinia) when soil remains saturated for 7+ consecutive days. The fibrous root systems lack adaptations for waterlogged conditions; oxygen levels below 2mg/L trigger cellular death that spreads from fine root hairs into larger root structures. Unlike succulents, begonias cannot switch to anaerobic respiration, making them particularly vulnerable to 'drowning' in peat-heavy mixes that retain moisture excessively.
How to Fix It
- 1
Emergency unpotting: Remove plant immediately from wet soil; gently rinse ALL soil from root system with lukewarm water
- 2
Surgical triage: Trim ALL black, mushy, or foul-smelling roots with 70% alcohol-sterilized scissors until only firm white tissue remains
- 3
Sterilization bath: Soak remaining roots in 3% hydrogen peroxide solution (1:1 with water) for 15-20 minutes to oxygenate tissue and kill surface pathogens
- 4
Callus period: Lay plant on dry paper towel in shaded area for 48 hours allowing cut wounds to seal and form protective scab
- 5
Repotting protocol: Use fresh mix of 50% high-quality potting soil, 30% perlite/pumice, 20% orchid bark; pot size should match root ball exactly with no excess soil
- 6
Recovery monitoring: Water only after 7 days post-repot; expect 4-8 week recovery before new growth emerges; do not fertilize for 6 weeks
How to Prevent It
Water only when top 2-3 inches bone-dry; use terracotta pots for moisture wicking; ensure drainage holes allow water exit within 30 seconds; avoid peat-heavy mixes without perlite amendment; maintain bright indirect light to support transpiration