This is one of our peonies.
It is a beautiful pink and blooms for quite awhile. I got it at the Urbana Farmers’ Market, where I am the Market Manager. When I bought it, it was only about a foot tall and there weren’t any buds on it yet. The vendor looked at the stem and said it was pink. She looked at another one and said it was white.
I thought that was rubbish… until I started looking at the stems as the peonies bloomed. It really does seem to be a good rule. I can’t say this works for every single peony out there, but it does appear to be a good rule of thumb at least.
We only have the dark pink peonies. Our vet, Dr. Corbett in Vinton, has several different peonies. I managed to get some pictures of his to see if the myth can be corroborated. It seems to work.
Light pink peony at my vet's office. (well okay, the cat's vet's office)
Stem from the light pink peony
White peony from Dr. Corbett's house
Stem of a white peony
A single peony at Dr. Corbett's house. "Single" means that it only has a single layer of petals.
Stem from the single dark pink peony at Dr. Corbett's
The single peony bush at Dr. Corbett's house
I haven’t seen anything published on this, but it appears to be a good rule of thumb. See if it works in your garden.