Hello: For the past few years the buds on several peonies are deformed, especially on an older planting of Red Charm. Recently, the same deformation is occuring on Lemon Chiffon which is only 3 years old. The buds are large, packed tightly and often have a hole in the centre and never open properly. If you have any ideas as to what is causing this problem, I would appreciate and information so very much as I cannot find an answer or solution to this condition.
Thank you for contacting the Toronto Master Gardeners. I’m sorry to hear about your suffering peonies! They’re one of my all-time favourite Spring blooms, so I can relate to how frustrating this must be!
Based on your description of the problem, especially the holes in the buds, it sounds like you may have Rose Chafer beetles (Macrodactylus subspinosus) preying on your peonies. The link provided to the OMAFRA site has excellent photos that when enlarged, can help you identify the insect.
The adult Rose Chafer feeds on a wide variety of flowers, fruits and leaves, and active from late May/early June until late June/early July. These insects lay their eggs in soil, and pupate in the spring, with adults feeding for 3 to 4 weeks. The females lay their eggs in the soil among weeds and grasses before they die. They prefer sandy soils, so this may also be a clue, if this is your soil type. The larvae feed on roots in the soil, with grubs burrowing below the frostline to overwinter.
This previous Toronto Master Gardener post provides several methods for controlling Rose Chafer beetles as well as links to additional resources. If you discover adults, put them into a pail of soapy water to kill them. Cultivation of the soil near the plant may also help to destroy egg clusters. Rose Chafers are a relatively slow-moving insect, but they are good fliers, which can allow them to travel some distance to find your plants.
If however the deformed blooms are misshapen in other ways, your problem may originate elsewhere. Sometimes several combined factors can contribute to no or poor blooming in peonies. This Toronto Master Gardeners post lists 8 potential factors for peony issues you could investigate, in case they are at play in your own garden. Another ailment impacting peonies is bud blast, which has a few interpretations but can be safely described as environmental and cultural factors, or fungal diseases, that individually or combined can lead to poor blooming performance. This article by the Missouri Botanical Garden covers bud blast in depth.