Nearby, Irene Loonga Alobo adjusted a fuzzy panda hat bought at the Great Wall and smiled at the attention it drew. "It's very cute and very comfortable," Alobo said. "But also, it's nice that China shares pandas with zoos across the world so everyone can enjoy them."

For the adults accompanying the group, those moments of delight formed part of a larger picture.

For Del Christensen, executive director of Iowa Sister States, the value of youth exchanges lies not only in what students see during a visit, but in what stays with them after they return home. "These young people may not be leaders today, but they may become leaders in the future, and the understanding they gain now will help them then," he said.

Reflecting on the friendship tree, he reached for an image that captured the continuity between generations. "The roots are the old friends that have been made between the United States and China," he said. "But all the branches and leaves are the new young friends."

Tamela Dawn Visalden, a teacher from Iowa on her first trip to China, said the visit showed her how much such exchanges can matter, especially for students who might otherwise never have had the chance to travel abroad.

Calling the "50,000 in Five Years" initiative "an amazing opportunity", she said it gave young people from the US not only a chance to experience Chinese culture, but also to interact directly with Chinese students. "My hope is that we can continue to come together and build a strong bond," she said.

For Berrone, that movement from observation to relationship is where the meaning of exchange begins. Its deeper value lies not in ceremony alone, but in the habits it builds — dialogue, respect and a willingness to learn from difference. "I cannot go to China and expect to find New York. Just like if you come to New York, you don't find Shanghai or Beijing," he said. "You have to respect the surroundings and cultural differences and learn from those."

Back beneath the ginkgo tree, the wish cards tied to its branches appear weightless in the spring breeze. Yet what they carry — peace, curiosity, gratitude and friendship — is anything but small.

Each exchange, Berrone said, is "like throwing a stone in the lake". No one can say exactly where the ripples will end up. Perhaps that is part of the point: their force is often felt later — in memory, in recognition, and in the quiet ways a brief encounter can widen into something lasting.

Contact the writers at zhaojia@chinadaily.com.cn