I bought one new peony from a local garden centre and I also have one old peony that I transplanted to a different location this spring. Both a herbaceous peonies. Because I learnt peonies require full sun so I planted them in a sunny location in my backyard where part of the garden bed gets some morning sun and hot afternoon sun for about 6 hours. I never thought peonies in southern Ontario would get too much sun, but mine seems getting burned a little?: new flower buds become black and stop increasing size and eventually dry out in a few days. Is this a sign that the plants are getting too much sun? The leaves all seem just fine.
Hello – Peonies need at least 6 hours of sun so I think your location is not the issue. Fungal disease or frost damage can cause peony buds to turn black and dry out (often called Bud Blast ) but the issue is also common on newly planted peonies. The buds are formed in the fall. Come the spring as they start to enlarge, the newly established root system is not yet robust enough to fully support the buds and they eventually dry up. As your foliage is in good shape, I suspect this is the case with your two new peonies. Your peonies will take a year or two to get established. An earlier post on our site offers advice on re-establishing peonies. Click on the link below to access the posting. Enjoy your garden.
https://www.torontomastergardeners.ca/askagardener/peony-not-blooming/