I use mower clippings every time, to fill in spaces where I want to kill weeds and expand my flower and shrub plantings. My garden and yard are completely untreated with chemicals, so I have no problem with safety for my plants or pets. You may have heard that using clippings spreads weeds, such as crabgrass or dandelions. As you can see from this photo, when the clippings are in the sun, they become airy and dry. Any seeds that the mower picks up will have a slim chance of rooting, because they aren’t sitting in dirt. All they have is this dry medium that also gets broiled under the sun. I use clippings in the summer, and add a layer of leaves in the fall, then add compost and topsoil the following spring/summer when I’m ready to plant. I may use a patch like this within a bed, to save the labor of weeding, but I also like to build weed-free borders around my beds with this layering method, and expland the area of beds, as above.