PopCap’s “Plants vs. Zombies,” a game in which you must fight off oncoming hordes of zombies using nothing more than, as the title suggests, plants, has climbed to to top of the charts and is now one of the highest grossing app on iTunes.

What’s most remarkable about this feat is the fact that Plants vs. Zombies became the third highest grossing app on the iTunes store in 9 days. Since then, it has been downloaded over 300,000 times, and has grossed in excess of $1 million.

So, what has made Plants. vs. Zombies so successful in such a short period of time? Here’s what Mike Schramm of The Unofficial Apple Weblog has to say:

“It’s a high quality game, first of all, and PopCap has a reputation for making those already. Second, the game itself had a fairly high profile even before release, since it was extremely successful on the PC as well. And finally, you have to think that the price figures in as well — I thought the game would sell for PopCap’s usual $5, but they actually sold it two dollars less than that. They’d probably have still made a lot of money, but I don’t know if they’d be talking about 300,000 sales at a price just two dollars higher.”

It is simply astounding that Apple’s App Store has grown from a small marketplace featuring only a few hundred apps, to a booming business where, with the right product, one can make millions in the span of less than two weeks.

Expect to see a full review of Plants vs. Zombies on iPhonefreak in the next few days!

Download Plants vs. Zombies here [$2.99]

Play the online version of Plants vs. Zombies here

[TUAW]