Troubleshooting
Soft-Stemmed Begonia problems — and how to fix them
Soft-Stemmed Begonia (Begonia mollicaulis) is generally low-drama, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Stem base rot (Pythium/Rhizoctonia)
The unusually soft stems collapse at soil level when the compost stays wet; use a very open mix, water sparingly, and ensure excellent drainage.
Mealybugs
White cottony masses appear at stem joints and leaf axils; treat by dabbing with isopropyl alcohol on a cotton bud and following up with insecticidal soap.
Prevent soft-stemmed begonia problems before they start
Most soft-stemmed begonia issues are care-mismatch, not bad luck. Dial in the basics:
Soft-Stemmed Begonia problems — FAQ
Why is my soft-stemmed begonia stem base rot (pythium/rhizoctonia)?
The unusually soft stems collapse at soil level when the compost stays wet; use a very open mix, water sparingly, and ensure excellent drainage.
Why is my soft-stemmed begonia mealybugs?
White cottony masses appear at stem joints and leaf axils; treat by dabbing with isopropyl alcohol on a cotton bud and following up with insecticidal soap.