Cold weather seldom bothers peonies. In fact they need a good cold period in order to grow properly. Certainly the lack of sun could definitely be the problem. Competing with too many other plants around them isn't helpful. A long-time peony grower suggested I not plant my new peonies too close to a Virbunum.

It also could be that they need a good dose of a good organic fertilizer like Espoma's Plant Tone, some Green Sand, and Super Phosphate if they haven't been encouraged in a long time. Good luck!

Thank you for your help! I'll try thinning out some of their neighbors and fertilizing them.

i think it may just be too early. i live across the river from detroit an peonies don't usually start here until mid-june. just wait them out. my irises have barely started, so i wouldn't be worried about the peonies just yet.

The original poster mentioned " I'll try thinning out some of their neighbors and fertilizing them". You can not just thin the stalks to make them bloom. If you were speaking of dividing that should be done in the fall. Which probably would be a good idea but wait until it is after September 1 to divide.