Plants vs. Zombies 2, the long-awaited sequel to PopCap Games’ incredibly popular tower defense title, has hit 16 million downloads worldwide in its opening week.

Electronic Arts is calling it their most successful mobile game launch ever, with players collectively planting 4 billion plants, destroying 2 billion zombie waves and grabbing 11 billion pieces of sunshine.

The title, available exclusively on the iPhone, iPad and iPod touch for now, is somewhat controversial given that it uses the free-to-play model, rather than an upfront fee on the App Store like the original. It seems that players are unfazed by the strategy though.

Press Release