Depends on what kind of tree to some extent. Depends on just how deep these leaves are when mulched as well. Also how much shade the grass is in. How new the grass is or how well established. I mulch some, shatter up and then pick up some, rake some. Leaves several inches deep do not mulch to well. Leaves several inches deep that get heavy wet snow on will mat down and kill grass and cannot be mulched worth a darn. Small sharp leaves just do not mulch at all in clumpy K31 grass as they embed themselves into the bottom of the clumps and then smother the fine fescue leaveing you with nothing but grass clumps after a few years. The same tree that provides those leaves here have long flexible stems that seperate and will weave themselves into bermuda grass so thick the grass suffers in the spring and the only way to get them out is mow the fall bermuda down to the ground or rake them up. The same tree provides seed pods a foot long to a few inches long and distributes them over a hundred feet around the tree often times several inches deep. These pods left in place will kill everything under them by spring and mulching them is pretty much impossible. The only person that can tell if mulching leaves is correct for the time and place is the person taking care of the leaves.
