Is it beneficial to leave grass clippings on the lawn after mowing?
Grass clippings left in lawn after mowing -- good or bad?
Certified GKH Gardening Expert
It is good if the clippings have time to dry out, or are not overly wet. If they are very wet, or it rains often in your area, then you may want to pull up the clippings and compost them. It all just depends on your environment really.
Grass clippings return valuable nutrients to soil, but they can cause fungal infection if they are too moist, or don't have time to dry out.
These articles will offer more information: