Stem Rot in String of Pearls — When the Threads Go Soft at the Base
String of Pearls (Curio rowleyanus (formerly Senecio rowleyanus))
Symptoms
- individual strands turning limp and collapsing near the soil line
- stem tissue at or below soil becoming brown, water-soaked, and soft
- beads on affected strands yellowing from the bottom up
- entire strands pulling free from soil with no resistance — root and stem detached
- gray-brown discoloration in the stem when cut open
Causes
Pythium or Rhizoctonia fungal pathogen in wet soil
Unlike root rot, which affects the underground root mass first, stem rot in String of Pearls attacks the stem at the soil surface — the point where moisture, organic matter, and fungal pathogens converge. Pythium ultimum and Rhizoctonia solani are the most common causes. Both require persistently wet soil to establish. Because String of Pearls stems are so slender, a fungal collar rot can kill an entire strand within 48–72 hours of infection.
Propagation cuttings planted with damaged stem ends in wet soil
When propagating String of Pearls from stem cuttings, damaged or crushed stem tissue is vulnerable to pathogen entry. Cuttings placed in wet soil without callusing first will often develop stem rot within days. The succulent parent plant may also develop rot where cuttings were taken if cuts were made with contaminated tools.
Splashing water directly onto stem-soil junction
Watering from above in a way that pools water at the base of strands keeps the stem-soil junction continuously moist — a localized overwatering effect even when the bulk of the pot is appropriately watered. Hanging baskets watered carelessly with a can that floods the center are especially vulnerable.
How to Fix It
- 1
Remove the affected strand immediately by cutting it at the first visibly healthy tissue above the rotted section. Do not try to save the rotted portion.
- 2
Inspect all neighboring strands. Gently trace each stem to the soil surface and feel for soft tissue. Rotted stems feel water-soaked and slightly slimy compared to firm healthy stems.
- 3
Allow the soil to dry completely. Do not water again until the soil is bone dry throughout the pot.
- 4
If multiple strands have rotted or the crown is affected, unpot the plant. Cut away all soft, brown, or water-soaked stem tissue. Dust cut surfaces with powdered sulfur or activated charcoal. Allow cut surfaces to callus for 48 hours before replanting in fresh, dry succulent mix.
- 5
Save healthy cuttings from unaffected strands. Let cut ends callus 24–48 hours, then lay on dry succulent mix. These will root and can replace the affected plant.
Prevention
- Water at the pot's edge or bottom-water to keep the stem-soil junction drier
- Allow cuttings to callus 24–48 hours before placing in soil
- Use sterile potting mix and clean pots when propagating
- Maintain correct watering frequency so soil does not remain wet for extended periods
Quick Summary
| Plant | String of Pearls (Curio rowleyanus (formerly Senecio rowleyanus)) |
|---|---|
| Category | Disease |
| Likely causes | Pythium or Rhizoctonia fungal pathogen in wet soil, Propagation cuttings planted with damaged stem ends in wet soil, Splashing water directly onto stem-soil junction |
| Fix steps | 5 steps — see above |