Expert: C.L. Fornari - 8/8/2009

Question
My hydrangea plants started to get a brown spot on the stems and leaves and eventually the leaves started withering and turning brown. I could not see any bugs or mites to cause this.  They became to withered and brown that I cut them back to the ground.
They are starting to grow again and the leaves are starting to get brown spots again.  Is this a fungus and if so what do I use to stop this?  

Answer
Sandra,
This is a leaf spot fungus - usually hydrangeas only get this if they are constantly sprinkled with water. If you live in an area where there has been an unusual amount of rain this summer, that would cause what you see. If you havean automatic irrigation system that is hitting them frequently, this too causes leaf spot on hydrangeas. You can't do anything about the rain, but irrigation should be adjusted so that it doesn't hit leaves and only goes on every four or five days at most. Soaker hoses are the best way to water these plants.  You could try using an organic fungicide such as Serenade, but if they are splashed with water frequently even the most heavy-hitting fungicide won't help.

Sometimes you get leaf spot from other sources of water - drift from lawn irrigation, dripping from air conditioner etc. and this will do the same thing.

all the best,
C.L.