Jun 17, 2022 · The smaller the gap, the harder it'll be for weeds to pop through. 3. Regularly Spray Vinegar on Weedy Areas. Acetic acid in vinegar helps dissolve the membranes of growing weeds, which kills them. Vinegar is a natural way to tackle the dilemma of weeds in rocks, but it likely won't do the job after one application.. Treat the soil with a pre-emergent herbicide before mulching. In some cases, especially around trees and shrubs, you can also lay down landscape fabric before mulching. It lets air and water into the soil but blocks weeds from growing. Edging around your mulched beds can also help discourage stray seeds from winding up in your mulch. .