American Express on Tuesday began letting lovers of Zynga games plant money trees on "Farmville" acreage.
The financial services titan known for high-status credit cards unveiled an alliance with the San Francisco based social games star.
Players of Zynga's popular "FarmVille" will be able to earn in-game virtual money as rewards for using specially branded prepaid Serve cards from American Express for shopping out in the real world.
"We're thrilled to expand our relationship with Zynga and provide an easy way for players to earn Zynga virtual game cash by learning about Serve and signing up to receive the many benefits of our digital wallet," said American Express president of enterprise growth Dan Schulman.
"As the commerce landscape continues to change, and online and offline spending converges, Serve is focused on partnering with companies like Zynga to create unique value for our customers in the environments they love."
"FarmVille" lets players tend to virtual crops with help from friends at leading social network Facebook or Zynga's recently-opened online playground at zynga.com.
Players were given the option of planting "Serve Money Trees" on their make-believe farms.
Those who plant trees are prompted to register Serve cards, load them with real money and then use them for purchases at US shops where American Express cards are accepted.
Doing so gives rise to crops of "Farm Cash" that can be harvested and spent in Zynga games.
"We're excited to partner with American Express to invent new ways for people to experience Zynga play in more parts of their day," said Mark Pincus CEO and Founder of Zynga. "Together we can add surprise and delight to everyday shopping."
American Express planned to expand the ways virtual cash crops could be cultivated, and the reward system was to eventually spread to "CastleVille" and "CityVille."
Information about the program was available online at serve.com/Zynga.
Explore further: Mexico City proposes regulations for Uber