Because people sometimes find common ants on a bouquet of peonies, a mythical explanation is that peonies need ants to bloom. Not true.
Ants and peonies do help each other. Ants eat the sweet nectar on peony blooms, and the pugnacious ants discourage some other floral-feeding insects, to the ant and peony mutual benefit. Ants don’t harm the peonies or cause peonies to open. If ants on the bouquet are a problem, dunk the flowers gently in a pail of water to remove them.
Common ants are less often called pollinators (like bees and butterflies) for the pollen they disperse when gathering nectar.
Ants do have a role in some seed dispersal. Just as wild cherry fruit attracts birds which disperse the seeds, some 11,000 species of wildflowers have an appendage on their seeds that is an ant food source.
Some seeds drop in place, and ants carry other seeds to the nest. Violets have these seed appendages. Violets may appear to move short distances with the help of ant seed dispersal. The November/December 2020 The American Gardener has more on the topic.