PopCap Games launched a social game adaptation of its Plants vs. Zombies tower defense franchise on Chinese social network Renren today. The developer told us last month that “what happens in Asia stays in Asia,” so we don’t expect to see a United States release of the title for Facebook anytime soon.

Plants vs. Zombies is played in series of increasingly difficult battle encounters where zombies progress across a lawn toward a house. The player fights off the zombies by planting various flowers, shrubs, and other garden variety plants in the lawn that then attack the zombies with different powers or defend other attacking plants. The social element for the Renren game comes from player “towns” that the player decorates to reflect their combat style (see below). Players can visit each other’s towns, but beyond that we’re not sure what they may do with this feature.

The Renren game also adds a new gameplay mode to Plants vs. Zombies called Rampage, where players must fight off a two-minute zombie onslaught. Scores in Rampage mode are tracked on a leaderboard. The game will feature weekly Rampage challenges.

Plants vs. Zombies for Renren was developed by PopCap’s Shanghai studio, which opened its doors in summer of 2008. PopCap’s strategy for Asia has been one of patience and emphasis on regional development, meaning that the developer avoids direct translations of its games to the region. Instead, the regional studio builds the game for the regional audience from the ground up, ensuring that the gameplay fits the audience. This is why we haven’t seen a Plants vs. Zombies game for Facebook here, yet; according to John Vechy, PopCap co-founder and VP of corporate strategy and development, PopCap has already cancelled roughly three different Facebook versions of the game so far because they didn’t feel right for the U.S. audience.

PopCap’s next move for Facebook will likely come from its newly-acquired studio, ZipZapPlay. The developer is also reportedly considering an initial public offering before the end of the year.