"Flower Power" was a 1960s slogan, used by hippies and other people who were against war and violence. These people used flowers as a symbol of life, of love, and of peace. They wore flowers, made art with flowers and images of them, and gave them away often. Hippies sometimes placed flowers in the rifle barrels of marching soldiers.
Songs such as San Francisco, Be Sure to Wear Flowers in Your Hair by folk musicians The Mamas & the Papas were associated with flower power.