Mulching beds is an important part of a sustainable landscape.
Pulling weeds is a job that never stops. Every time weeds are removed, new weed seeds germinate, creating the problem all over again.
Mulches work to stop this by blocking sunlight from reaching the soil service. Most weed seeds need light to germinate. The light tells them they're close enough to the soil surface to sprout and grow a new plant.
Cover a weed seed with mulch, and these seeds will sense that they are too deep into the soil and will not germinate. To create this barrier preventing weed growth, mulch must be applied thick enough to have the sunlight-blocking effect. Apply organic mulches at least two inches thick for the best weed control.