Weeds are nasty, ugly, and invasive. They steal water and nutrients from the plants you love. If you pull them out, they grow right back. They hog the sun, and act like garden bullies. Even so, you can't bring yourself to spray them into oblivion. So, how do you naturally keep them out of your garden? Simple. With mulch.
Weeds need light and warm soil to survive. To use mulch as a natural weed inhibitor, you need to put down at least 3 inches. That's enough to keep most weed seeds or roots from being activated. They won't have enough energy to push through.
Different mulches have different uses. Pebbles and small stones can be considered mulch, but they are not organic and don't amend the soil. Straw is often used in vegetable gardens, but it tends to contain many weed seeds. Grass clippings are also popular, but they lack aesthetic appeal. Your best bet is bark mulch, such as Scotts® Nature Scapes Advanced Color Enhanced Mulch. It gives your garden a clean, finished look while holding down weeds. Also, since it's organic, it amends your soil as it breaks down.
If you have a bed of perennials, wait until the flowers push through. Then lay down mulch all around them. Put your annuals in first and then mulch the surrounding area. At three inches or more of mulch, your weed problems will be minimized.