Four entrants, Jo Thompson, James Basson, Kazuyuki Ishihara and Jihae Hwang, were at Chelsea this year.
The event is held in a large replica 17th-century Dutch theme park.
Its proximity is close to Nagasaki, blitzed by an atomic bomb in world War II. The brief is themed on gardens for world peace and was conceived by Japanese designer Kazuyuki Ishihara.
Thompson, returning a second time, said: "My experience last year, where I narrowly missed a gold medal, has helped me to plan this year’s design. The Butterfly Effect garden is my response to the atomic shadows I saw at the Peace Park and museum.
"The intricate and beautiful shadows of leaves and flowers, burnt onto walls by the blast, made me consider the fact that such delicate patterns could be caused by something so brutally ugly."
Event newcomer Richard Miers said: "My garden, Serenity, is a pocket of living green in an urban environment with a very English subtext. There is a symmetry and use of numbers that challenges the way the Japanese think about outdoor spaces.
"The unraked gravel is a practical solution to surfacing on a budget. The herbaceous planting, ferns and moss mounds are however my interpretation of Japanese design so there is an east meets west element to this place."
Visitors to the Gardening World Cup will see work by the best designers from New Zealand, North America, Europe and the Far East. The competitors have two weeks to build their gardens ahead of a televised Oscar style ceremony on 28 September.
Lim in Chong
David Davidson and Leon Kluge