Even Jesus needs to eat. So when he hungrily approaches a fig tree and finds—gasp!—only leaves, he curses it. And we're not talking about giving it the middle finger. He actually dooms it to death and perpetual barrenness (11:12-14). Later that evening, on their way back from Jerusalem, Peter notices that the poor little fig tree is utterly withered (11:20-21).
Okay, so why on earth does Mark include this information? It can't possibly be to make us think Jesus is spoiled and testy, can it?
The key is the text that falls between these two incidents in 11:15-19—that is, after Jesus curses the tree, but before they see it withered. Mark actually uses this technique quite a bit. He inserts one story between two parts of another story; the pros call that "sandwiching" (you can also see it in 6:7-31 and 5:21-43). The trick is to realize that the two stories that compose the narrative BLT are to be interpreted in light of one another. Is anyone else getting hungry?
Back to this particular case. The inner story here in details Jesus's "temple tantrum", during which he crashes the commerce party in the temple precinct. His objection isn't to the temple, but to the way it has been corrupted by its current leadership.
Think about that in terms of the whole fig tree scenario. Jesus's curse of the fig tree takes on the figurative or even allegorical significance of a curse against the temple itself. Of course, many of the early recipients of Mark's gospel would have known about the destruction of the temple by the Romans at the end of the Jewish War in 70 CE. Could Jesus's curse be another reference to this event?