One last thought: If you are looking for a really good motion blur (usually only matters in animation) the best way to do that is to render out a velocity channel through Render Elements. Use that in Combustion to generate Combustion's motion blur. It's a faster way when dealing with a large sequnce of frames and can be adjusted in Combustion.
I think we would all like to conquer this challange in Max, but if push comes to shove with your still, you can always render the leaf out as "selected" with an alpha and apply the motion blur with a Photoshop filter (a bit of a hack, but will work).