Garden Pests and Diseases: Black Spots on Peony, 0 by DonnaMack

DonnaMack wrote:
Birder is right in that this is not a big deal, but I\'ll make a bet that your previous owner did not cut down their peony foliage at the the end of the season, and that they had not done it for years. I have a client with a bunch of peonies they had not cut down for years and they had this. A person I used to work with had it too.

I think that what you are describing is phytophthora blight. It\'s a fungal disease that produces black spots. Nothing fatal.

See this:
http://blog.pennlive.com/gardening/2012/07/black_spots_all_o...

I used a fungicide on both groups of affected peonies last year and this year it is much reduced. It\'s not a terrible thing - it\'s just not pretty. I personally cut my peonies to the ground each fall, and have year after year and I have never experienced what you are seeing.

Don\'t worry. It won\'t kill them. It just will rob you of the beauty of the fall foliage (see below).

It\'s too late to do anything about it now, but you might want to make sure that you cut down all of your peony foliage at the end of the season and use a good organic fungicide like sulphur (made cheaply by Bonide and Safer). Use it more than once a couple of weeks apart. Make sure that the temperature is under 80 degrees so that you don\'t burn the foliage. Spray the ground around them. Repeat it in spring, since the spores may still be around.

Peony foliage can actually be quite beautiful in the fall. I leave mine up as long as possible.

I do not know what effect it will have on your tropicals but I suspect the answer is none.