2011-09-22 : For Garruk’s second ability, the greatest power among creatures you control is determined when that ability begins resolving.

2011-09-22 : For Garruk’s third ability, the number of Wurm tokens you put onto the battlefield is determined when that ability begins resolving.

2011-09-22 : If the greatest power among creatures you control is 0 or less, you’ll draw no cards. You won’t discard any cards this way.