The answer to 'mulch has weeds' is that weeds can easily grow in mulch if the mulch is not properly maintained. Mulch provides an ideal environment for weeds to take root and thrive, as it retains moisture and blocks sunlight from reaching the soil. Common causes include using low-quality mulch, not replenishing it regularly, or not properly preparing the area before applying the mulch.
Symptoms of weeds in mulch include seeing new weed growth popping up through the mulch, or the mulch becoming discolored and matted down as weeds spread. To solve this issue, you'll need to remove the existing weeds, then reapply a fresh layer of high-quality mulch 2-4 inches deep. It's best to call a professional landscaper if the weed problem is extensive or if you're unsure how to properly maintain the mulch going forward.