Leaf stains on your concrete can seem like an impossible task when it comes to removal. The natural bleaching of the sun will likely remove the stains in time but if you are looking for a way to remove them faster you can try using a detergent designed to remove organic stains. Dry granular detergents are useful as they will add additional friction. Make sure you use a pressure washer to clear the debris and allow the detergent to soak in for a few mins. Then scrup vigorously. Oxyclean is another detergent that can help also.