It is typical for peony buds to have ants crawling all over them. There has been quite a controversy as to the purpose of this or whether the ants should be removed or left alone. It has been proven that they do no harm to the peony plants or flowers. The peonies do not get any known benefit from the ants.
It has been said ants on buds of peony flowers enable the blossoms to bloom. Ants are often also given credit for fluffing out the petals of the flowers once they do bloom. This is just a myth. The flowers would open and fluff even in an ant-free environment.
Peonies have glands called extrafloral nectarines that deposit sap on the buds. This sap is made up mostly of sugar but also contains protein, amino acids and other nutrients. No wonder ants love peony buds; they are attracted to the buds' sweet sap.
Even though ants are not instrumental in opening the buds, they do serve a purpose. Ants are aggressive and will either eat or drive other pests away that harm peonies. Therefore, it is best to just leave them alone and let them feast on the sap.
Ants do not stay around long after the flowers bloom and the nutrient-rich sap is no longer produced. It is only created while the flower is still a bud. A few ants may be reluctant to leave the flowers, but once they are fully open, the ants will be gone.
It is important to prevent bringing ants inside when using peonies as cut flowers. There are several ways to do this. Cut the flowers and dip the head of the flower in a bucket of clear water. Gently swish it around until all ants fall into the water. Remove the flower from the water and shake gently to remove excess water and any ants that have held on. Another method is to cut the flowers while they are still buds. Wait until the bud starts to open and the color of the petals can be seen. Lightly squeeze the bud. If it is hard, do not pick yet; it is not ready. Once the bud feels like the consistency of a large marshmallow, it is ready to pick. Wipe all the ants off the bud before taking it into the house. Put the stems in water and the bud will open within 24 hours.