I've had no luck with Do Tell for some reason, finally got a 1st year plant to put out a bloom last year after several tries so I don't know if I have any good advice....that said, there are plenty of varieties of peony that really need to be divided more often than others. Some develop more of a "woody crown" on the roots than others and start to fail after a while. Once divided and with the woody part of the root minimized they can be replanted and will grow well again. I honestly don't know if Do Tell is one of those....Another thing that I would check is the ground immediately over the root, below the foliage. Make sure it's not sunken and that it doesn't have water sitting on it too much after rains or watering. The other more vigorous peonies on either side might be crowding the roots. If it's not one of those 3 things I'm stumped, sorry. Also want to tell you there is a more active peony forum at https://garden.org/forums/view/peonies/ , some of us are on both but there are a lot of experienced peony growers who only go to that one, might get someone with specific variety knowledge there. Good luck, Do Tell is a very pretty peony, hope you can save it!

Thanks for all the suggestions. I'm sure it's not standing in water. I'll try dividing it and planting it somewhere else and see if that helps. It performed magnificently for me for many years - it was one of my favourite herbaceaous peonies in my garden - so I hope that will revive it.

Will you be digging it up soon? I would be very interested to know the cause of its decline. If it is not too much trouble, can you post a pic of the root after it is dug with the dirt removed? It may help others with similar problems in the future. Thanks.

I'll take a photo when I dig it up, likely in about three weeks.

Since your plant has been in the ground for ten years do not be surprised how it looks. It may be completely woody.

Interesting. I had thought that peonies could live happily undisturbed for decades. Is it like lizbest1 said, that it depends on the variety? (I have about 20 peonies that are about that age, and most are doing fine.)

Thanks lizbest1, you were totally right. The crown was woody and rotted. Unfortunately, what growth there was seems to have been sprouting from rotten roots. Now that I see, there's no wonder it was doing poorly - the real surprise is that it was putting up any kind of growth at all. I literally have not been able to find a single healthy eye, so I'm not sure what to do about replanting.

I'd go with the stems and roots around the edges, looks like you have some decent feeder roots. I'd just get rid of most of the middle

Thank you for sharing your pic of Do Tell. I have never seen a root with such badly rotting crown. It is really strange that this peony is so susceptible to this development than the peonies that are nearby. In fact, you have a tree peony next to it. I have always heard that tree peonies are more prone to rotting than herbaceous and yet your tree peony looks extremely healthy. If it is a fussy peony, I am amazed that you have been able to grow it and had it done well for 10 years!

Some peonies just struggle. There is no reason for it. Surrounding plants are not effected nor do they have an effect. Most people will have at least one plant of some kind that they just can not grow even though their neighbor or friends may not have any problems. Do Tell is one of those plants that I have learned through other peoples comments that either do extremely well or struggle and eventually die. Some from the time they were planted others several years later.