Leave the mulch alone for best weed suppression. You should rake or hoe it if you want to work the bark into the soil and improve the drainage and aeration, like if you are growing seeds or veggies or planting new annuals. Most weeds come from above when you have a bark mulch, and it is hard to sprout on top of bark. When you hoe or rake you expose bare soil that is full of old weed seeds and the sunlight can now cause these once buried seeds to germinate. That said, you must hoe or pull any weeds you see in the bed as early as possible. Letting weeds go to seed will just cause more weeds to sprout all over your garden. Remove the weeds but disturb the mulch as little as necessary. So who wins that bet? Keep growing, Marianne Binetti