I love blade edging because it gives all hard and soft edges a clean line; much better than anything a line trimmer could do. But as you bury the metal blade into your edges, you inevitably kick up dirt which collects in the blade cover. Then, later it falls out in a black soil ball and becomes noticeable.
When you do your clean-up blow, you must sweat the details. One of them is eliminating the black soil ball from your lawn by either blowing it away or better yet, picking it up.
Leaving it on your freshly cut lawn is not an option.
Vas Sladek, B.Sc., CLHT