I removed the cuttings in past years, but it doesn't seem to have an effect. I think every inch of soil is throroughly saturated with a large variety of seeds. After whacking it down it's just a smooth carpet of green. So I gave up on the removal as not worth the effort.
If you leave the cuttings they'll decompose and fertilize the soil, giving advantage to fast growing weeds. Possibly also add nitrogen deposition from surrounding industry/agriculture to that, and you have an ideal cycle for lots of biomass. Mowing like twice a year and removing cuttings on the other hand can and usually does break that cycle, can take some years, resulting in less fierce growth, and more slow-growing species.
Is this a garden of a yard you are maintaining? Cultivating a garden before you see weeds cuts down on the weed seed bank. One of those things that takes rigorous practice for a year or more before it is obviously having a long term positive impact.
It's the opposite of a garden, it's a rural lot next to several million acres of wilderness forest. Everything growing here is a volunteer, there is no lawn, I've planted nothing.
And there's plenty of wind constantly bringing more volunteers. This time of year I can almost see them growing.
