How do I plant cocoa beans?

I've got two cocoa beans and would love to plant them, but I can't seem to figure out how.

You cannot plant cocoa beans in Minecraft versions below 1.3.1. As the wiki says, they can only be used as dyes and to make cookies and they can only be found in chests in dungeons.

As of 1.3.1, you can plant cocoa beans on the side of jungle trees to grow cocoa plants, from which you can harvest more cocoa beans.

As of the 1.3.1 release cocoa beans may be "planted" on the trunks of jungle trees. There they become a green pod that turns orange as it grows. When harvested the mature pods release several beans.