Question
I have three tropical hibiscus trees. They were growing and flowering beautifully all summer, but I live in western North Carolina and had to bring them in for the winter. After bringing them in the house they started to drop their leaves and now only two of them have any leaves at all. Also one of my trees has developed a bright yellow colored substance that looks like a fungus in the dirt around the base of the plant. Can you tell me how to fix this problem? Also I think that another of the trees has developed root rot or a similar problem. Half of the tree has leaves and looks healthy, but the other half of the tree has died completely and when I checked to see if it was dead the stem just pulled right off in my hand and it looked like it had rotted from the inside out. What would cause this?

Answer
Hi Ellen,
Thanx for your question.  It does sound to me like you have a fungal issue and one that is best resolved by destroying the affected plants.  It is common for tropical hibiscus to drop leaves in the winter.  The low position of the sun in the sky and the shortened day lenghth pushes the plant into a semi-dormancy.  Generally, this isn't harmful to the plant and it is recommended that watering be kept at a minimum, just enough to keep the plant alive during this period.  Excess watering will cause fungal and mold problems.  The air is full of mold and fungus spores and the disease in your plants could have come from anywhere.  Cut away all dead and/or affected parts of the plant and discard.  The plant that has the yellow mold around it should be dug up and all the diseased roots removed.  Spray with a fungicidal spray you can find at a local nursery.  Plant in a different pot with different soil or discard the whole plant.  If the plants survive, next time you bring them in, water them minimally as too much moisture and cool temps during dormancy are the common causes for fungal infection.  I hope this helps.
Tom